subprojects: Prepare for release

The C glue code depends on its fields for now.

inject/inject.vala

@@ -147,7 +147,7 @@ namespace Frida.Inject {
 		public extern void init ();
 	}
 
-	public class Application : Object {
+	public sealed class Application : Object {
 		public string? device_id {
 			get;
 			construct;
@@ -426,7 +426,7 @@ namespace Frida.Inject {
 #endif
 	}
 
-	private class ScriptRunner : Object, RpcPeer {
+	private sealed class ScriptRunner : Object, RpcPeer {
 		public TerminalMode terminal_mode {
 			get;
 			private set;

lib/agent/agent.vala

@@ -11,7 +11,7 @@ namespace Frida.Agent {
 		PROCESS_TRANSITION
 	}
 
-	private class Runner : Object, ProcessInvader, AgentSessionProvider, ExitHandler, ForkHandler, SpawnHandler {
+	private sealed class Runner : Object, ProcessInvader, AgentSessionProvider, ExitHandler, ForkHandler, SpawnHandler {
 		public static Runner shared_instance = null;
 		public static Mutex shared_mutex;
 		private static string? cached_agent_path = null;
@@ -1621,7 +1621,7 @@ namespace Frida.Agent {
 	}
 #endif
 
-	private class LiveAgentSession : BaseAgentSession {
+	private sealed class LiveAgentSession : BaseAgentSession {
 		public uint registration_id {
 			get;
 			set;

lib/base/buffer.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class BufferBuilder : Object {
+	public sealed class BufferBuilder : Object {
 		public ByteOrder byte_order {
 			get;
 			construct;
@@ -307,7 +307,7 @@ namespace Frida {
 		NUL
 	}
 
-	public class Buffer : Object {
+	public sealed class Buffer : Object {
 		public Bytes bytes {
 			get;
 			construct;
@@ -466,7 +466,7 @@ namespace Frida {
 		}
 	}
 
-	public class BufferReader {
+	public sealed class BufferReader {
 		public size_t available {
 			get {
 				return buffer.bytes.get_size () - offset;

lib/base/channel.vala

@@ -0,0 +1,240 @@
+namespace Frida {
+	public sealed class ChannelRegistry : Object {
+		public signal void channel_closed (ChannelId id);
+
+		private Gee.Map<ChannelId?, weak IOStream> channels =
+			new Gee.HashMap<ChannelId?, weak IOStream> (ChannelId.hash, ChannelId.equal);
+
+		~ChannelRegistry () {
+			clear ();
+		}
+
+		public void clear () {
+			foreach (IOStream stream in channels.values.to_array ()) {
+				var channel_stream = stream as ChannelStream;
+				if (channel_stream != null)
+					channel_stream.abandon ();
+			}
+			channels.clear ();
+		}
+
+		public void register (ChannelId id, IOStream stream) {
+			stream.set_data ("channel-registry-entry", new Entry (this, id));
+			lock (channels)
+				channels[id] = stream;
+		}
+
+		public IOStream link (ChannelId id) throws Error {
+			IOStream? stream;
+			lock (channels)
+				stream = channels[id];
+			if (stream == null)
+				throw new Error.INVALID_ARGUMENT ("Invalid channel ID");
+			return stream;
+		}
+
+		public void unlink (ChannelId id) {
+			lock (channels) {
+				if (!channels.unset (id))
+					return;
+			}
+
+			channel_closed (id);
+		}
+
+		private class Entry {
+			public ChannelRegistry parent;
+			public ChannelId id;
+
+			public Entry (ChannelRegistry parent, ChannelId id) {
+				this.parent = parent;
+				this.id = id;
+			}
+
+			~Entry () {
+				parent.unlink (id);
+			}
+		}
+	}
+
+	public sealed class ChannelEndpoint : Object, Channel {
+		private IOStream? stream;
+
+		private ByteArray write_queue = new ByteArray ();
+		private bool writing = false;
+
+		private Cancellable io_cancellable = new Cancellable ();
+
+		public ChannelEndpoint (IOStream stream) {
+			this.stream = stream;
+
+			read_loop.begin ();
+		}
+
+		public async void close (Cancellable? cancellable) throws Error, IOError {
+			io_cancellable.cancel ();
+		}
+
+		public async void input (uint8[] data, Cancellable? cancellable) throws Error, IOError {
+			if (io_cancellable.is_cancelled ())
+				throw new Error.INVALID_OPERATION ("Channel is closed");
+
+			write_queue.append (data);
+
+			if (!writing) {
+				writing = true;
+
+				var source = new IdleSource ();
+				source.set_callback (() => {
+					process_write_queue.begin ();
+					return false;
+				});
+				source.attach (MainContext.get_thread_default ());
+			}
+		}
+
+		private async void read_loop () {
+			var input = stream.get_input_stream ();
+			var buffer = new uint8[64 * 1024];
+
+			while (true) {
+				ssize_t n;
+				try {
+					n = yield input.read_async (buffer, Priority.DEFAULT, io_cancellable);
+				} catch (GLib.Error e) {
+					break;
+				}
+
+				output (buffer[:n]);
+			}
+
+			stream.close_async.begin ();
+			stream = null;
+		}
+
+		private async void process_write_queue () {
+			if (stream != null) {
+				var output = stream.get_output_stream ();
+
+				while (write_queue.len > 0) {
+					uint8[] batch = write_queue.steal ();
+
+					size_t bytes_written;
+					try {
+						yield output.write_all_async (batch, Priority.DEFAULT, io_cancellable, out bytes_written);
+					} catch (GLib.Error e) {
+						break;
+					}
+				}
+			}
+
+			writing = false;
+		}
+	}
+
+	public sealed class ChannelStream : VirtualStream {
+		public Channel channel {
+			get;
+			construct;
+		}
+
+		private ByteArray recv_queue = new ByteArray ();
+		private ByteArray send_queue = new ByteArray ();
+
+		public ChannelStream (Channel channel) {
+			Object (channel: channel);
+		}
+
+		construct {
+			channel.output.connect (on_output);
+		}
+
+		public void abandon () {
+			with_state_lock (() => {
+				state = CLOSED;
+				update_pending_io ();
+			});
+		}
+
+		protected override IOCondition query_events () {
+			IOCondition new_events = 0;
+
+			if (recv_queue.len != 0 || state == CLOSED)
+				new_events |= IN;
+
+			if (state == OPEN)
+				new_events |= OUT;
+
+			return new_events;
+		}
+
+		protected override void handle_close () {
+			channel.close.begin (null);
+		}
+
+		public override ssize_t read (uint8[] buffer) throws IOError {
+			ssize_t n = 0;
+			with_state_lock (() => {
+				n = ssize_t.min (recv_queue.len, buffer.length);
+				if (n > 0) {
+					Memory.copy (buffer, recv_queue.data, n);
+					recv_queue.remove_range (0, (uint) n);
+
+					update_pending_io ();
+				} else {
+					if (state == OPEN)
+						n = -1;
+				}
+			});
+
+			if (n == -1)
+				throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
+
+			return n;
+		}
+
+		public override ssize_t write (uint8[] buffer) throws IOError {
+			with_state_lock (() => {
+				send_queue.append (buffer);
+			});
+
+			if (main_context.is_owner ()) {
+				process_send_queue ();
+			} else {
+				var source = new IdleSource ();
+				source.set_callback (() => {
+					process_send_queue ();
+					return Source.REMOVE;
+				});
+				source.attach (main_context);
+			}
+
+			return buffer.length;
+		}
+
+		private void process_send_queue () {
+			uint8[]? chunk = null;
+			with_state_lock (() => {
+				size_t n = send_queue.len;
+				if (n == 0)
+					return;
+				chunk = send_queue.data[0:n];
+				send_queue.remove_range (0, (uint) n);
+			});
+			if (chunk == null)
+				return;
+
+			channel.input.begin (chunk, io_cancellable);
+		}
+
+		private void on_output (uint8[] data) {
+			with_state_lock (() => {
+				if (data.length != 0)
+					recv_queue.append (data);
+				else
+					state = CLOSED;
+				update_pending_io ();
+			});
+		}
+	}
+}

lib/base/corefoundation.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class CFArray<T> {
+	public sealed class CFArray<T> {
 		private CoreFoundation.Array handle;
 
 		public static CFArray<T> wrap<T> (void * handle) {

lib/base/dbus.vala

@@ -60,7 +60,7 @@ namespace Frida {
 		return yield connection.get_proxy (null, ObjectPath.HOST_SESSION, DBusProxyFlags.NONE, cancellable);
 	}
 
-	private class DummyInputStream : InputStream {
+	private sealed class DummyInputStream : InputStream {
 		private bool done = false;
 		private Mutex mutex;
 		private Cond cond;

lib/base/meson.build

@@ -1,6 +1,9 @@
 base_sources = [
   'session.vala',
   'session-glue.c',
+  'channel.vala',
+  'service.vala',
+  'stream.vala',
   'rpc.vala',
   'p2p.vala',
   'p2p-glue.c',

lib/base/p2p.vala

@@ -169,7 +169,7 @@ namespace Frida {
 		}
 	}
 
-	public class PeerSocket : Object, DatagramBased {
+	public sealed class PeerSocket : Object, DatagramBased {
 		public Nice.Agent agent {
 			get;
 			construct;
@@ -452,6 +452,8 @@ namespace Frida {
 				if ((_pending_io & c) != 0)
 					source.set_ready_time (0);
 			}
+
+			notify_property ("pending-io");
 		}
 
 		private void prepare_for_io (int64 timeout, Cancellable? cancellable, out int64 deadline) throws IOError {
@@ -563,7 +565,7 @@ namespace Frida {
 		}
 	}
 
-	public class SctpConnection : IOStream {
+	public sealed class SctpConnection : VirtualStream {
 		public DatagramBased transport_socket {
 			get;
 			construct;
@@ -584,55 +586,14 @@ namespace Frida {
 			construct;
 		}
 
-		public State state {
-			get {
-				return _state;
-			}
-		}
-
-		public override InputStream input_stream {
-			get {
-				return _input_stream;
-			}
-		}
-
-		public override OutputStream output_stream {
-			get {
-				return _output_stream;
-			}
-		}
-
-		public IOCondition pending_io {
-			get {
-				lock (state)
-					return sctp_events;
-			}
-		}
-
-		private State _state = CREATED;
-		private SctpInputStream _input_stream;
-		private SctpOutputStream _output_stream;
-
 		private DatagramBasedSource transport_source;
 		private uint8[] transport_buffer = new uint8[65536];
 
 		private void * sctp_socket;
-		private IOCondition sctp_events = 0;
 		private SctpTimerSource sctp_source;
 		private uint16 stream_id;
 		private ByteArray dcep_message = new ByteArray ();
 
-		private Gee.Map<unowned Source, IOCondition> sources = new Gee.HashMap<unowned Source, IOCondition> ();
-
-		private Cancellable io_cancellable = new Cancellable ();
-
-		public enum State {
-			CREATED,
-			OPENING,
-			OPENED,
-			CLOSED
-		}
-
 		public SctpConnection (DatagramBased transport_socket, PeerSetup setup, uint16 port, size_t max_message_size) {
 			Object (
 				transport_socket: transport_socket,
@@ -649,14 +610,9 @@ namespace Frida {
 		protected extern static void _initialize_sctp_backend ();
 
 		construct {
-			_input_stream = new SctpInputStream (this);
-			_output_stream = new SctpOutputStream (this);
-
 			sctp_socket = _create_sctp_socket ();
 			_connect_sctp_socket (sctp_socket, port);
 
-			var main_context = MainContext.get_thread_default ();
-
 			transport_source = transport_socket.create_source (IOCondition.IN, io_cancellable);
 			transport_source.set_callback (on_transport_socket_readable);
 			transport_source.attach (main_context);
@@ -669,17 +625,22 @@ namespace Frida {
 
 		protected extern void _connect_sctp_socket (void * sock, uint16 port);
 
-		public override bool close (GLib.Cancellable? cancellable) throws IOError {
-			do_close ();
-			return true;
+		protected override VirtualStream.State query_initial_state () {
+			return CREATED;
 		}
 
-		public override async bool close_async (int io_priority, GLib.Cancellable? cancellable) throws IOError {
-			do_close ();
-			return true;
+		protected override IOCondition query_events () {
+			return _query_sctp_socket_events (sctp_socket);
 		}
 
-		private void do_close () {
+		protected override void update_pending_io () {
+			base.update_pending_io ();
+			sctp_source.invalidate ();
+		}
+
+		protected extern static IOCondition _query_sctp_socket_events (void * sock);
+
+		protected override void handle_close () {
 			sctp_source.destroy ();
 			transport_source.destroy ();
 
@@ -689,13 +650,17 @@ namespace Frida {
 
 		public extern static void _close (void * sock);
 
-		public void shutdown (SctpShutdownType type) throws IOError {
-			_shutdown (sctp_socket, type);
+		public override void shutdown_read () throws IOError {
+			_shutdown (sctp_socket, READ);
+		}
+
+		public override void shutdown_write () throws IOError {
+			_shutdown (sctp_socket, WRITE);
 		}
 
 		public extern static void _shutdown (void * sock, SctpShutdownType type) throws IOError;
 
-		public ssize_t recv (uint8[] buffer) throws IOError {
+		public override ssize_t read (uint8[] buffer) throws IOError {
 			ssize_t n = -1;
 
 			try {
@@ -711,18 +676,18 @@ namespace Frida {
 						handle_dcep_message (stream_id, dcep_message.steal ());
 					}
 					throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
-				} else if (protocol_id == NONE || _state != OPENED) {
+				} else if (protocol_id == NONE || state != OPEN) {
 					throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
 				}
 			} finally {
-				update_sctp_events ();
+				update_pending_io ();
 			}
 
 			return n;
 		}
 
-		public ssize_t send (uint8[] buffer) throws IOError {
-			if (_state != OPENED)
+		public override ssize_t write (uint8[] buffer) throws IOError {
+			if (state != OPEN)
 				throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
 
 			ssize_t n = ssize_t.min (buffer.length, (ssize_t) max_message_size);
@@ -730,20 +695,10 @@ namespace Frida {
 			try {
 				return _send (sctp_socket, stream_id, WEBRTC_BINARY, buffer[0:n]);
 			} finally {
-				update_sctp_events ();
+				update_pending_io ();
 			}
 		}
 
-		public void register_source (Source source, IOCondition condition) {
-			lock (state)
-				sources[source] = condition | IOCondition.ERR | IOCondition.HUP;
-		}
-
-		public void unregister_source (Source source) {
-			lock (state)
-				sources.unset (source);
-		}
-
 		private bool on_transport_socket_readable (DatagramBased datagram_based, IOCondition condition) {
 			var v = InputVector ();
 			v.buffer = transport_buffer;
@@ -783,9 +738,9 @@ namespace Frida {
 		}
 
 		protected void _on_sctp_socket_events_changed () {
-			update_sctp_events ();
+			update_pending_io ();
 
-			if (_state == CREATED && setup == ACTIVE && (sctp_events & IOCondition.OUT) != 0) {
+			if (state == CREATED && setup == ACTIVE && (pending_io & IOCondition.OUT) != 0) {
 				stream_id = 1;
 
 				uint8[] open_message = {
@@ -799,31 +754,12 @@ namespace Frida {
 				};
 				try {
 					_send (sctp_socket, stream_id, WEBRTC_DCEP, open_message);
-					_state = OPENING;
+					state = OPENING;
 				} catch (IOError e) {
 				}
 			}
 		}
 
-		private void update_sctp_events () {
-			IOCondition new_events = _query_sctp_socket_events (sctp_socket);
-
-			lock (state) {
-				sctp_events = new_events;
-
-				foreach (var entry in sources.entries) {
-					unowned Source source = entry.key;
-					IOCondition c = entry.value;
-					if ((new_events & c) != 0)
-						source.set_ready_time (0);
-				}
-
-				sctp_source.invalidate ();
-			}
-		}
-
-		protected extern static IOCondition _query_sctp_socket_events (void * sock);
-
 		protected extern static ssize_t _recv (void * sock, uint8[] buffer, out uint16 stream_id,
 			out PayloadProtocolId protocol_id, out SctpMessageFlags message_flags) throws IOError;
 
@@ -835,7 +771,7 @@ namespace Frida {
 
 			switch (type) {
 				case DATA_CHANNEL_OPEN: {
-					if (_state != CREATED || setup == ACTIVE)
+					if (state != CREATED || setup == ACTIVE)
 						return;
 
 					this.stream_id = stream_id;
@@ -843,15 +779,15 @@ namespace Frida {
 					uint8[] reply = { DcepMessageType.DATA_CHANNEL_ACK };
 					_send (sctp_socket, stream_id, WEBRTC_DCEP, reply);
 
-					_state = OPENED;
+					state = OPEN;
 
 					break;
 				}
 				case DATA_CHANNEL_ACK:
-					if (_state != OPENING)
+					if (state != OPENING)
 						return;
 
-					_state = OPENED;
+					state = OPEN;
 
 					break;
 			}
@@ -886,140 +822,6 @@ namespace Frida {
 		DATA_CHANNEL_ACK = 0x02
 	}
 
-	private class SctpInputStream : InputStream, PollableInputStream {
-		public weak SctpConnection connection {
-			get;
-			construct;
-		}
-
-		public SctpInputStream (SctpConnection connection) {
-			Object (connection: connection);
-		}
-
-		public override bool close (Cancellable? cancellable) throws IOError {
-			connection.shutdown (READ);
-			return true;
-		}
-
-		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-			return close (cancellable);
-		}
-
-		public override ssize_t read (uint8[] buffer, Cancellable? cancellable) throws IOError {
-			assert_not_reached ();
-		}
-
-		public bool can_poll () {
-			return true;
-		}
-
-		public bool is_readable () {
-			return (connection.pending_io & IOCondition.IN) != 0;
-		}
-
-		public PollableSource create_source (Cancellable? cancellable) {
-			return new PollableSource.full (this, new SctpIOSource (connection, IOCondition.IN), cancellable);
-		}
-
-		public ssize_t read_nonblocking_fn (uint8[] buffer) throws GLib.Error {
-			return connection.recv (buffer);
-		}
-	}
-
-	private class SctpOutputStream : OutputStream, PollableOutputStream {
-		public weak SctpConnection connection {
-			get;
-			construct;
-		}
-
-		public SctpOutputStream (SctpConnection connection) {
-			Object (connection: connection);
-		}
-
-		public override bool close (Cancellable? cancellable) throws IOError {
-			connection.shutdown (WRITE);
-			return true;
-		}
-
-		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-			return close (cancellable);
-		}
-
-		public override bool flush (GLib.Cancellable? cancellable) throws GLib.Error {
-			return true;
-		}
-
-		public override async bool flush_async (int io_priority, GLib.Cancellable? cancellable) throws GLib.Error {
-			return true;
-		}
-
-		public override ssize_t write (uint8[] buffer, Cancellable? cancellable) throws IOError {
-			assert_not_reached ();
-		}
-
-		public bool can_poll () {
-			return true;
-		}
-
-		public bool is_writable () {
-			return (connection.pending_io & IOCondition.OUT) != 0;
-		}
-
-		public PollableSource create_source (Cancellable? cancellable) {
-			return new PollableSource.full (this, new SctpIOSource (connection, IOCondition.OUT), cancellable);
-		}
-
-		public ssize_t write_nonblocking_fn (uint8[]? buffer) throws GLib.Error {
-			return connection.send (buffer);
-		}
-
-		public PollableReturn writev_nonblocking_fn (OutputVector[] vectors, out size_t bytes_written) throws GLib.Error {
-			assert_not_reached ();
-		}
-	}
-
-	private class SctpIOSource : Source {
-		public SctpConnection connection;
-		public IOCondition condition;
-
-		public SctpIOSource (SctpConnection connection, IOCondition condition) {
-			this.connection = connection;
-			this.condition = condition;
-
-			connection.register_source (this, condition);
-		}
-
-		~SctpIOSource () {
-			connection.unregister_source (this);
-		}
-
-		protected override bool prepare (out int timeout) {
-			timeout = -1;
-			return (connection.pending_io & condition) != 0;
-		}
-
-		protected override bool check () {
-			return (connection.pending_io & condition) != 0;
-		}
-
-		protected override bool dispatch (SourceFunc? callback) {
-			set_ready_time (-1);
-
-			if (callback == null)
-				return Source.REMOVE;
-
-			return callback ();
-		}
-
-		protected static bool closure_callback (Closure closure) {
-			var return_value = Value (typeof (bool));
-
-			closure.invoke (ref return_value, {});
-
-			return return_value.get_boolean ();
-		}
-	}
-
 	private class SctpTimerSource : Source {
 		private static int64 last_process_time = -1;
 

lib/base/promise.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class Promise<T> {
+	public sealed class Promise<T> {
 		private Impl<T> impl;
 
 		public Future<T> future {

lib/base/rpc.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class RpcClient : Object {
+	public sealed class RpcClient : Object {
 		public weak RpcPeer peer {
 			get;
 			construct;

lib/base/service.vala

@@ -0,0 +1,48 @@
+namespace Frida {
+	public sealed class ServiceSessionRegistry : Object {
+		public signal void session_closed (ServiceSessionId id);
+
+		private Gee.Map<ServiceSessionId?, ServiceSession> sessions =
+			new Gee.HashMap<ServiceSessionId?, ServiceSession> (ServiceSessionId.hash, ServiceSessionId.equal);
+
+		~ServiceSessionRegistry () {
+			clear ();
+		}
+
+		public void clear () {
+			foreach (var session in sessions.values.to_array ())
+				session.close ();
+			sessions.clear ();
+		}
+
+		public void register (ServiceSessionId id, ServiceSession session) {
+			sessions[id] = session;
+
+			ServiceSessionId? boxed_id = id;
+			session.set_data ("service-session-id", boxed_id);
+
+			session.close.connect (on_session_close);
+		}
+
+		public ServiceSession link (ServiceSessionId id) throws Error {
+			var session = sessions[id];
+			if (session == null)
+				throw new Error.INVALID_ARGUMENT ("Invalid session ID");
+			return session;
+		}
+
+		public void unlink (ServiceSessionId id) {
+			ServiceSession? session;
+			if (sessions.unset (id, out session)) {
+				session.close.disconnect (on_session_close);
+
+				session_closed (id);
+			}
+		}
+
+		private void on_session_close (ServiceSession session) {
+			ServiceSessionId? id = session.get_data ("service-session-id");
+			unlink (id);
+		}
+	}
+}

lib/base/session.vala

@@ -27,6 +27,10 @@ namespace Frida {
 		public abstract async InjectorPayloadId inject_library_blob (uint pid, uint8[] blob, string entrypoint, string data,
 			Cancellable? cancellable) throws GLib.Error;
 
+		public abstract async ChannelId open_channel (string address, Cancellable? cancellable) throws GLib.Error;
+
+		public abstract async ServiceSessionId open_service (string address, Cancellable? cancellable) throws GLib.Error;
+
 		public signal void spawn_added (HostSpawnInfo info);
 		public signal void spawn_removed (HostSpawnInfo info);
 		public signal void child_added (HostChildInfo info);
@@ -34,6 +38,8 @@ namespace Frida {
 		public signal void process_crashed (CrashInfo crash);
 		public signal void output (uint pid, int fd, uint8[] data);
 		public signal void agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash);
+		public signal void channel_closed (ChannelId id);
+		public signal void service_session_closed (ServiceSessionId id);
 		public signal void uninjected (InjectorPayloadId id);
 	}
 
@@ -145,7 +151,7 @@ namespace Frida {
 		DEBUGGER
 	}
 
-	public class AgentMessageTransmitter : Object {
+	public sealed class AgentMessageTransmitter : Object {
 		public signal void closed ();
 		public signal void new_candidates (string[] candidate_sdps);
 		public signal void candidate_gathering_done ();
@@ -743,6 +749,23 @@ namespace Frida {
 		}
 	}
 
+	[DBus (name = "re.frida.Channel16")]
+	public interface Channel : Object {
+		public abstract async void close (Cancellable? cancellable) throws GLib.Error;
+		public abstract async void input (uint8[] data, Cancellable? cancellable) throws GLib.Error;
+		public signal void output (uint8[] data);
+	}
+
+	[DBus (name = "re.frida.ServiceSession16")]
+	public interface ServiceSession : Object {
+		public signal void close ();
+		public signal void message (Variant message);
+
+		public abstract async void activate (Cancellable? cancellable) throws GLib.Error;
+		public abstract async void cancel (Cancellable? cancellable) throws GLib.Error;
+		public abstract async Variant request (Variant parameters, Cancellable? cancellable) throws GLib.Error;
+	}
+
 	[DBus (name = "re.frida.TransportBroker16")]
 	public interface TransportBroker : Object {
 		public abstract async void open_tcp_transport (AgentSessionId id, Cancellable? cancellable, out uint16 port,
@@ -770,7 +793,7 @@ namespace Frida {
 		public abstract async string authenticate (string token, Cancellable? cancellable) throws GLib.Error;
 	}
 
-	public class StaticAuthenticationService : Object, AuthenticationService {
+	public sealed class StaticAuthenticationService : Object, AuthenticationService {
 		public string token_hash {
 			get;
 			construct;
@@ -795,13 +818,13 @@ namespace Frida {
 		}
 	}
 
-	public class NullAuthenticationService : Object, AuthenticationService {
+	public sealed class NullAuthenticationService : Object, AuthenticationService {
 		public async string authenticate (string token, Cancellable? cancellable) throws Error, IOError {
 			throw new Error.INVALID_OPERATION ("Authentication not expected");
 		}
 	}
 
-	public class UnauthorizedHostSession : Object, HostSession {
+	public sealed class UnauthorizedHostSession : Object, HostSession {
 		public async void ping (uint interval_seconds, Cancellable? cancellable) throws Error, IOError {
 			throw_not_authorized ();
 		}
@@ -875,9 +898,17 @@ namespace Frida {
 				Cancellable? cancellable) throws Error, IOError {
 			throw_not_authorized ();
 		}
+
+		public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+			throw_not_authorized ();
+		}
+
+		public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			throw_not_authorized ();
+		}
 	}
 
-	public class UnauthorizedPortalSession : Object, PortalSession {
+	public sealed class UnauthorizedPortalSession : Object, PortalSession {
 		public async void join (HostApplicationInfo app, SpawnStartState current_state,
 				AgentSessionId[] interrupted_sessions, HashTable<string, Variant> options,
 				Cancellable? cancellable, out SpawnStartState next_state) throws Error, IOError {
@@ -885,7 +916,7 @@ namespace Frida {
 		}
 	}
 
-	public class UnauthorizedBusSession : Object, BusSession {
+	public sealed class UnauthorizedBusSession : Object, BusSession {
 		public async void attach (Cancellable? cancellable) throws Error, IOError {
 			throw_not_authorized ();
 		}
@@ -1083,7 +1114,7 @@ namespace Frida {
 		}
 	}
 
-	public class FrontmostQueryOptions : Object {
+	public sealed class FrontmostQueryOptions : Object {
 		public Scope scope {
 			get;
 			set;
@@ -1113,7 +1144,7 @@ namespace Frida {
 		}
 	}
 
-	public class ApplicationQueryOptions : Object {
+	public sealed class ApplicationQueryOptions : Object {
 		public Scope scope {
 			get;
 			set;
@@ -1171,7 +1202,7 @@ namespace Frida {
 		}
 	}
 
-	public class ProcessQueryOptions : Object {
+	public sealed class ProcessQueryOptions : Object {
 		public Scope scope {
 			get;
 			set;
@@ -1313,7 +1344,7 @@ namespace Frida {
 		}
 	}
 
-	public class SessionOptions : Object {
+	public sealed class SessionOptions : Object {
 		public Realm realm {
 			get;
 			set;
@@ -1502,6 +1533,46 @@ namespace Frida {
 		}
 	}
 
+	public struct ChannelId {
+		public string handle;
+
+		public ChannelId (string handle) {
+			this.handle = handle;
+		}
+
+		public ChannelId.generate () {
+			this.handle = Uuid.string_random ().replace ("-", "");
+		}
+
+		public static uint hash (ChannelId? id) {
+			return id.handle.hash ();
+		}
+
+		public static bool equal (ChannelId? a, ChannelId? b) {
+			return a.handle == b.handle;
+		}
+	}
+
+	public struct ServiceSessionId {
+		public string handle;
+
+		public ServiceSessionId (string handle) {
+			this.handle = handle;
+		}
+
+		public ServiceSessionId.generate () {
+			this.handle = Uuid.string_random ().replace ("-", "");
+		}
+
+		public static uint hash (ServiceSessionId? id) {
+			return id.handle.hash ();
+		}
+
+		public static bool equal (ServiceSessionId? a, ServiceSessionId? b) {
+			return a.handle == b.handle;
+		}
+	}
+
 	public struct AgentScriptId {
 		public uint handle;
 
@@ -1518,7 +1589,7 @@ namespace Frida {
 		}
 	}
 
-	public class ScriptOptions : Object {
+	public sealed class ScriptOptions : Object {
 		public string? name {
 			get;
 			set;
@@ -1608,7 +1679,7 @@ namespace Frida {
 		SHARED_MEMORY
 	}
 
-	public class SnapshotOptions : Object {
+	public sealed class SnapshotOptions : Object {
 		public string? warmup_script {
 			get;
 			set;
@@ -1683,7 +1754,7 @@ namespace Frida {
 		}
 	}
 
-	public class PortalOptions : Object {
+	public sealed class PortalOptions : Object {
 		public TlsCertificate? certificate {
 			get;
 			set;
@@ -1746,7 +1817,7 @@ namespace Frida {
 		}
 	}
 
-	public class PeerOptions : Object {
+	public sealed class PeerOptions : Object {
 		public string? stun_server {
 			get;
 			set;
@@ -1807,7 +1878,7 @@ namespace Frida {
 		}
 	}
 
-	public class Relay : Object {
+	public sealed class Relay : Object {
 		public string address {
 			get;
 			construct;
@@ -2048,7 +2119,8 @@ namespace Frida {
 		public const string AGENT_SESSION = "/re/frida/AgentSession";
 		public const string AGENT_CONTROLLER = "/re/frida/AgentController";
 		public const string AGENT_MESSAGE_SINK = "/re/frida/AgentMessageSink";
-		public const string CHILD_SESSION = "/re/frida/ChildSession";
+		public const string CHANNEL = "/re/frida/Channel";
+		public const string SERVICE = "/re/frida/Service";
 		public const string TRANSPORT_BROKER = "/re/frida/TransportBroker";
 		public const string PORTAL_SESSION = "/re/frida/PortalSession";
 		public const string BUS_SESSION = "/re/frida/BusSession";
@@ -2061,6 +2133,14 @@ namespace Frida {
 		public static string for_agent_message_sink (AgentSessionId id) {
 			return AGENT_MESSAGE_SINK + "/" + id.handle;
 		}
+
+		public static string for_channel (ChannelId id) {
+			return CHANNEL + "/" + id.handle;
+		}
+
+		public static string for_service_session (ServiceSessionId id) {
+			return SERVICE + "/" + id.handle;
+		}
 	}
 
 	namespace Marshal {

lib/base/socket.vala

@@ -97,7 +97,7 @@ namespace Frida {
 		}
 	}
 
-	public class EndpointParameters : Object {
+	public sealed class EndpointParameters : Object {
 		public string? address {
 			get;
 			construct;
@@ -234,7 +234,7 @@ namespace Frida {
 		return (inet_addr.get_family () == IPV6) ? @"[$host]" : host;
 	}
 
-	public class WebService : Object {
+	public sealed class WebService : Object {
 		public signal void incoming (IOStream connection, SocketAddress remote_address, DynamicInterface? dynamic_iface);
 
 		public EndpointParameters endpoint_params {
@@ -852,7 +852,7 @@ namespace Frida {
 		public abstract void start ();
 	}
 
-	public class DynamicInterface : Object {
+	public sealed class DynamicInterface : Object {
 		public string name {
 			get;
 			construct;
@@ -870,7 +870,7 @@ namespace Frida {
 
 	public extern static unowned string _version_string ();
 
-	private class WebConnection : IOStream {
+	private sealed class WebConnection : VirtualStream {
 		public signal void websocket_closed ();
 
 		public Soup.WebsocketConnection websocket {
@@ -878,37 +878,9 @@ namespace Frida {
 			construct;
 		}
 
-		public override InputStream input_stream {
-			get {
-				return _input_stream;
-			}
-		}
-
-		public override OutputStream output_stream {
-			get {
-				return _output_stream;
-			}
-		}
-
-		public IOCondition pending_io {
-			get {
-				lock (state)
-					return _pending_io;
-			}
-		}
-
-		private WebInputStream _input_stream;
-		private WebOutputStream _output_stream;
-
-		private Soup.WebsocketState state;
-		private IOCondition _pending_io;
 		private ByteArray recv_queue = new ByteArray ();
 		private ByteArray send_queue = new ByteArray ();
 
-		private Gee.Map<unowned Source, IOCondition> sources = new Gee.HashMap<unowned Source, IOCondition> ();
-
-		private MainContext main_context;
-
 		public WebConnection (Soup.WebsocketConnection websocket) {
 			Object (websocket: websocket);
 		}
@@ -916,14 +888,6 @@ namespace Frida {
 		construct {
 			websocket.max_incoming_payload_size = (256 * 1024) + 1; // XXX: There's an off-by-one error in libsoup
 
-			_input_stream = new WebInputStream (this);
-			_output_stream = new WebOutputStream (this);
-
-			state = websocket.state;
-			_pending_io = (state == OPEN) ? IOCondition.OUT : IOCondition.IN;
-
-			main_context = MainContext.ref_thread_default ();
-
 			websocket.closed.connect (on_closed);
 			websocket.message.connect (on_message);
 		}
@@ -933,51 +897,50 @@ namespace Frida {
 			websocket.closed.disconnect (on_closed);
 		}
 
-		public override bool close (GLib.Cancellable? cancellable) throws IOError {
-			_close ();
-			return true;
-		}
-
-		public override async bool close_async (int io_priority, GLib.Cancellable? cancellable) throws IOError {
-			_close ();
-			return true;
-		}
-
-		private void _close () {
-			if (main_context.is_owner ()) {
-				do_close ();
-			} else {
-				var source = new IdleSource ();
-				source.set_callback (() => {
-					do_close ();
-					return Source.REMOVE;
-				});
-				source.attach (main_context);
+		protected override VirtualStream.State query_initial_state () {
+			switch (websocket.state) {
+				case OPEN:
+				case CLOSING:
+					return OPEN;
+				case CLOSED:
+					return CLOSED;
 			}
+			assert_not_reached ();
 		}
 
-		private void do_close () {
+		protected override IOCondition query_events () {
+			IOCondition new_events = 0;
+
+			if (recv_queue.len > 0 || state != OPEN)
+				new_events |= IN;
+
+			if (state == OPEN)
+				new_events |= OUT;
+
+			return new_events;
+		}
+
+		protected override void handle_close () {
 			if (websocket.state != OPEN)
 				return;
 
 			websocket.close (1000, "Closing");
 		}
 
-		public ssize_t recv (uint8[] buffer) throws IOError {
-			ssize_t n;
-			lock (state) {
+		public override ssize_t read (uint8[] buffer) throws IOError {
+			ssize_t n = 0;
+			with_state_lock (() => {
 				n = ssize_t.min (recv_queue.len, buffer.length);
 				if (n > 0) {
 					Memory.copy (buffer, recv_queue.data, n);
 					recv_queue.remove_range (0, (uint) n);
 
-					recompute_pending_io_unlocked ();
+					update_pending_io ();
 				} else {
 					if (state == OPEN)
 						n = -1;
 				}
-
-			}
+			});
 
 			if (n == -1)
 				throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
@@ -985,9 +948,10 @@ namespace Frida {
 			return n;
 		}
 
-		public ssize_t send (uint8[] buffer) {
-			lock (state)
+		public override ssize_t write (uint8[] buffer) {
+			with_state_lock (() => {
 				send_queue.append (buffer);
+			});
 
 			if (main_context.is_owner ()) {
 				process_send_queue ();
@@ -1011,190 +975,34 @@ namespace Frida {
 
 			while (true) {
 				uint8[]? chunk = null;
-				lock (state) {
+				with_state_lock (() => {
 					size_t n = size_t.min (send_queue.len, max_message_size);
 					if (n == 0)
 						return;
 					chunk = send_queue.data[0:n];
 					send_queue.remove_range (0, (uint) n);
-				}
+				});
+				if (chunk == null)
+					return;
 
 				websocket.send_binary (chunk);
 			}
 		}
 
-		public void register_source (Source source, IOCondition condition) {
-			lock (state)
-				sources[source] = condition;
-		}
-
-		public void unregister_source (Source source) {
-			lock (state)
-				sources.unset (source);
-		}
-
 		private void on_closed () {
-			lock (state) {
-				state = websocket.state;
-				recompute_pending_io_unlocked ();
-			}
+			with_state_lock (() => {
+				state = CLOSED;
+				update_pending_io ();
+			});
 
 			websocket_closed ();
 		}
 
 		private void on_message (int type, Bytes message) {
-			lock (state) {
+			with_state_lock (() => {
 				recv_queue.append (message.get_data ());
-				recompute_pending_io_unlocked ();
-			}
-		}
-
-		private void recompute_pending_io_unlocked () {
-			IOCondition new_io = 0;
-			if (recv_queue.len > 0 || state != OPEN)
-				new_io |= IN;
-			if (state == OPEN)
-				new_io |= OUT;
-			_pending_io = new_io;
-
-			foreach (var entry in sources.entries) {
-				unowned Source source = entry.key;
-				IOCondition c = entry.value;
-				if ((new_io & c) != 0)
-					source.set_ready_time (0);
-			}
-		}
-	}
-
-	private class WebInputStream : InputStream, PollableInputStream {
-		public weak WebConnection connection {
-			get;
-			construct;
-		}
-
-		public WebInputStream (WebConnection connection) {
-			Object (connection: connection);
-		}
-
-		public override bool close (Cancellable? cancellable) throws IOError {
-			return true;
-		}
-
-		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-			return close (cancellable);
-		}
-
-		public override ssize_t read (uint8[] buffer, Cancellable? cancellable) throws IOError {
-			assert_not_reached ();
-		}
-
-		public bool can_poll () {
-			return true;
-		}
-
-		public bool is_readable () {
-			return (connection.pending_io & IOCondition.IN) != 0;
-		}
-
-		public PollableSource create_source (Cancellable? cancellable) {
-			return new PollableSource.full (this, new WebIOSource (connection, IOCondition.IN), cancellable);
-		}
-
-		public ssize_t read_nonblocking_fn (uint8[] buffer) throws GLib.Error {
-			return connection.recv (buffer);
-		}
-	}
-
-	private class WebOutputStream : OutputStream, PollableOutputStream {
-		public weak WebConnection connection {
-			get;
-			construct;
-		}
-
-		public WebOutputStream (WebConnection connection) {
-			Object (connection: connection);
-		}
-
-		public override bool close (Cancellable? cancellable) throws IOError {
-			return true;
-		}
-
-		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-			return close (cancellable);
-		}
-
-		public override bool flush (GLib.Cancellable? cancellable) throws GLib.Error {
-			return true;
-		}
-
-		public override async bool flush_async (int io_priority, GLib.Cancellable? cancellable) throws GLib.Error {
-			return true;
-		}
-
-		public override ssize_t write (uint8[] buffer, Cancellable? cancellable) throws IOError {
-			assert_not_reached ();
-		}
-
-		public bool can_poll () {
-			return true;
-		}
-
-		public bool is_writable () {
-			return (connection.pending_io & IOCondition.OUT) != 0;
-		}
-
-		public PollableSource create_source (Cancellable? cancellable) {
-			return new PollableSource.full (this, new WebIOSource (connection, IOCondition.OUT), cancellable);
-		}
-
-		public ssize_t write_nonblocking_fn (uint8[]? buffer) throws GLib.Error {
-			return connection.send (buffer);
-		}
-
-		public PollableReturn writev_nonblocking_fn (OutputVector[] vectors, out size_t bytes_written) throws GLib.Error {
-			assert_not_reached ();
-		}
-	}
-
-	private class WebIOSource : Source {
-		public WebConnection connection;
-		public IOCondition condition;
-
-		public WebIOSource (WebConnection connection, IOCondition condition) {
-			this.connection = connection;
-			this.condition = condition;
-
-			connection.register_source (this, condition);
-		}
-
-		~WebIOSource () {
-			connection.unregister_source (this);
-		}
-
-		protected override bool prepare (out int timeout) {
-			timeout = -1;
-			return (connection.pending_io & condition) != 0;
-		}
-
-		protected override bool check () {
-			return (connection.pending_io & condition) != 0;
-		}
-
-		protected override bool dispatch (SourceFunc? callback) {
-			set_ready_time (-1);
-
-			if (callback == null)
-				return Source.REMOVE;
-
-			return callback ();
-		}
-
-		protected static bool closure_callback (Closure closure) {
-			var return_value = Value (typeof (bool));
-
-			closure.invoke (ref return_value, {});
-
-			return return_value.get_boolean ();
+				update_pending_io ();
+			});
 		}
 	}
 }

lib/base/stream.vala

@@ -0,0 +1,334 @@
+namespace Frida {
+	public abstract class VirtualStream : IOStream {
+		public override InputStream input_stream {
+			get {
+				return _input_stream;
+			}
+		}
+
+		public override OutputStream output_stream {
+			get {
+				return _output_stream;
+			}
+		}
+
+		public IOCondition pending_io {
+			get {
+				lock (state)
+					return _pending_io;
+			}
+		}
+
+		protected State state = OPEN;
+
+		private VirtualInputStream _input_stream;
+		private VirtualOutputStream _output_stream;
+
+		private IOCondition _pending_io;
+
+		private Gee.Map<unowned Source, IOCondition> sources = new Gee.HashMap<unowned Source, IOCondition> ();
+
+		protected Cancellable io_cancellable = new Cancellable ();
+
+		protected MainContext main_context;
+
+		protected enum State {
+			CREATED,
+			OPENING,
+			OPEN,
+			CLOSED
+		}
+
+		protected delegate void WorkFunc ();
+
+		construct {
+			_input_stream = new VirtualInputStream (this);
+			_output_stream = new VirtualOutputStream (this);
+
+			main_context = MainContext.ref_thread_default ();
+
+			state = query_initial_state ();
+			_pending_io = query_events ();
+		}
+
+		public override void dispose () {
+			_output_stream.detach ();
+			_input_stream.detach ();
+
+			io_cancellable.cancel ();
+
+			base.dispose ();
+		}
+
+		protected virtual State query_initial_state () {
+			return OPEN;
+		}
+
+		protected abstract IOCondition query_events ();
+
+		public override bool close (GLib.Cancellable? cancellable) throws IOError {
+			_close ();
+			return true;
+		}
+
+		public override async bool close_async (int io_priority, GLib.Cancellable? cancellable) throws IOError {
+			_close ();
+			return true;
+		}
+
+		private void _close () {
+			if (main_context.is_owner ()) {
+				do_close ();
+			} else {
+				var source = new IdleSource ();
+				source.set_callback (() => {
+					do_close ();
+					return Source.REMOVE;
+				});
+				source.attach (main_context);
+			}
+		}
+
+		private void do_close () {
+			if (state == CLOSED)
+				return;
+
+			handle_close ();
+		}
+
+		protected abstract void handle_close ();
+
+		public virtual void shutdown_read () throws IOError {
+		}
+
+		public virtual void shutdown_write () throws IOError {
+		}
+
+		public abstract ssize_t read (uint8[] buffer) throws IOError;
+
+		public abstract ssize_t write (uint8[] buffer) throws IOError;
+
+		protected void with_state_lock (WorkFunc func) {
+			lock (state)
+				func ();
+		}
+
+		public void register_source (Source source, IOCondition condition) {
+			lock (state)
+				sources[source] = condition | IOCondition.ERR | IOCondition.HUP;
+		}
+
+		public void unregister_source (Source source) {
+			lock (state)
+				sources.unset (source);
+		}
+
+		protected virtual void update_pending_io () {
+			_pending_io = query_events ();
+
+			foreach (var entry in sources.entries) {
+				unowned Source source = entry.key;
+				IOCondition c = entry.value;
+				if ((_pending_io & c) != 0)
+					source.set_ready_time (0);
+			}
+
+			notify_property ("pending-io");
+		}
+	}
+
+	private sealed class VirtualInputStream : InputStream, PollableInputStream {
+		private weak VirtualStream stream;
+
+		public VirtualInputStream (VirtualStream stream) {
+			Object ();
+			this.stream = stream;
+		}
+
+		internal void detach () {
+			stream = null;
+		}
+
+		public override bool close (Cancellable? cancellable) throws IOError {
+			if (stream != null)
+				stream.shutdown_read ();
+			return true;
+		}
+
+		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
+			return close (cancellable);
+		}
+
+		public override ssize_t read (uint8[] buffer, Cancellable? cancellable) throws IOError {
+			if (stream == null)
+				return 0;
+
+			if (!is_readable ()) {
+				bool done = false;
+				var mutex = Mutex ();
+				var cond = Cond ();
+
+				ulong io_handler = stream.notify["pending-io"].connect ((obj, pspec) => {
+					if (is_readable ()) {
+						mutex.lock ();
+						done = true;
+						cond.signal ();
+						mutex.unlock ();
+					}
+				});
+				ulong cancellation_handler = 0;
+				if (cancellable != null) {
+					cancellation_handler = cancellable.connect (() => {
+						mutex.lock ();
+						done = true;
+						cond.signal ();
+						mutex.unlock ();
+					});
+				}
+
+				if (!is_readable ()) {
+					mutex.lock ();
+					while (!done)
+						cond.wait (mutex);
+					mutex.unlock ();
+				}
+
+				if (cancellation_handler != 0)
+					cancellable.disconnect (cancellation_handler);
+				stream.disconnect (io_handler);
+
+				cancellable.set_error_if_cancelled ();
+			}
+
+			return stream.read (buffer);
+		}
+
+		public bool can_poll () {
+			return true;
+		}
+
+		public bool is_readable () {
+			if (stream == null)
+				return true;
+			return (stream.pending_io & IOCondition.IN) != 0;
+		}
+
+		public PollableSource create_source (Cancellable? cancellable) {
+			return new PollableSource.full (this, new VirtualIOSource (stream, IOCondition.IN), cancellable);
+		}
+
+		public ssize_t read_nonblocking_fn (uint8[] buffer) throws GLib.Error {
+			if (stream == null)
+				return 0;
+			return stream.read (buffer);
+		}
+	}
+
+	private sealed class VirtualOutputStream : OutputStream, PollableOutputStream {
+		private weak VirtualStream? stream;
+
+		public VirtualOutputStream (VirtualStream stream) {
+			Object ();
+			this.stream = stream;
+		}
+
+		internal void detach () {
+			stream = null;
+		}
+
+		public override bool close (Cancellable? cancellable) throws IOError {
+			if (stream != null)
+				stream.shutdown_write ();
+			return true;
+		}
+
+		public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
+			return close (cancellable);
+		}
+
+		public override bool flush (GLib.Cancellable? cancellable) throws GLib.Error {
+			return true;
+		}
+
+		public override async bool flush_async (int io_priority, GLib.Cancellable? cancellable) throws GLib.Error {
+			return true;
+		}
+
+		public override ssize_t write (uint8[] buffer, Cancellable? cancellable) throws IOError {
+			return stream.write (buffer);
+		}
+
+		public bool can_poll () {
+			return true;
+		}
+
+		public bool is_writable () {
+			if (stream == null)
+				return false;
+			return (stream.pending_io & IOCondition.OUT) != 0;
+		}
+
+		public PollableSource create_source (Cancellable? cancellable) {
+			return new PollableSource.full (this, new VirtualIOSource (stream, IOCondition.OUT), cancellable);
+		}
+
+		public ssize_t write_nonblocking_fn (uint8[]? buffer) throws GLib.Error {
+			if (stream == null)
+				throw new IOError.CLOSED ("Virtual is closed");
+			return stream.write (buffer);
+		}
+
+		public PollableReturn writev_nonblocking_fn (OutputVector[] vectors, out size_t bytes_written) throws GLib.Error {
+			assert_not_reached ();
+		}
+	}
+
+	private class VirtualIOSource : Source {
+		public VirtualStream? stream;
+		public IOCondition condition;
+
+		public VirtualIOSource (VirtualStream stream, IOCondition condition) {
+			this.stream = stream;
+			this.condition = condition;
+
+			if (stream != null)
+				stream.register_source (this, condition);
+		}
+
+		~VirtualIOSource () {
+			if (stream != null)
+				stream.unregister_source (this);
+		}
+
+		protected override bool prepare (out int timeout) {
+			timeout = -1;
+			return is_ready ();
+		}
+
+		protected override bool check () {
+			return is_ready ();
+		}
+
+		private bool is_ready () {
+			IOCondition pending_io = (stream != null) ? stream.pending_io : IOCondition.IN;
+			return (pending_io & condition) != 0;
+		}
+
+		protected override bool dispatch (SourceFunc? callback) {
+			set_ready_time (-1);
+
+			if (callback == null)
+				return Source.REMOVE;
+
+			return callback ();
+		}
+
+		protected static bool closure_callback (Closure closure) {
+			var return_value = Value (typeof (bool));
+
+			closure.invoke (ref return_value, {});
+
+			return return_value.get_boolean ();
+		}
+	}
+}

lib/base/value.vala

@@ -38,7 +38,7 @@ namespace Frida {
 		public abstract unowned string get_uuid_value () throws Error;
 	}
 
-	public class VariantReader : Object, ObjectReader {
+	public sealed class VariantReader : Object, ObjectReader {
 		public Variant root_object {
 			get {
 				return scopes.peek_head ().val;
@@ -180,7 +180,7 @@ namespace Frida {
 		}
 	}
 
-	public class JsonObjectBuilder : Object, ObjectBuilder {
+	public sealed class JsonObjectBuilder : Object, ObjectBuilder {
 		private Json.Builder builder = new Json.Builder ();
 		private Gee.Map<string, Bytes> raw_values = new Gee.HashMap<string, Bytes> ();
 
@@ -267,7 +267,7 @@ namespace Frida {
 		}
 	}
 
-	public class JsonObjectReader : Object, ObjectReader {
+	public sealed class JsonObjectReader : Object, ObjectReader {
 		private Json.Reader reader;
 
 		public JsonObjectReader (string json) throws Error {

lib/base/xpc.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class XpcClient : Object {
+	public sealed class XpcClient : Object {
 		public signal void message (Darwin.Xpc.Object obj);
 
 		public State state {
@@ -123,7 +123,7 @@ namespace Frida {
 		}
 	}
 
-	public class XpcObjectReader {
+	public sealed class XpcObjectReader {
 		public Darwin.Xpc.Object root_object {
 			get {
 				return scopes.peek_head ().object;

lib/gadget/gadget.vala

@@ -1,5 +1,5 @@
 namespace Frida.Gadget {
-	private class Config : Object, Json.Serializable {
+	private sealed class Config : Object, Json.Serializable {
 		public Object interaction {
 			get;
 			set;
@@ -93,7 +93,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ScriptInteraction : Object, Json.Serializable {
+	private sealed class ScriptInteraction : Object, Json.Serializable {
 		public string path {
 			get;
 			set;
@@ -145,7 +145,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ScriptDirectoryInteraction : Object {
+	private sealed class ScriptDirectoryInteraction : Object {
 		public string path {
 			get;
 			set;
@@ -164,7 +164,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ScriptConfig : Object, Json.Serializable {
+	private sealed class ScriptConfig : Object, Json.Serializable {
 		public ProcessFilter? filter {
 			get;
 			set;
@@ -216,7 +216,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ProcessFilter : Object {
+	private sealed class ProcessFilter : Object {
 		public string[] executables {
 			get;
 			set;
@@ -258,7 +258,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ListenInteraction : SocketInteraction {
+	private sealed class ListenInteraction : SocketInteraction {
 		public PortConflictBehavior on_port_conflict {
 			get;
 			set;
@@ -287,7 +287,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ConnectInteraction : SocketInteraction, Json.Serializable {
+	private sealed class ConnectInteraction : SocketInteraction, Json.Serializable {
 		public string[]? acl {
 			get;
 			set;
@@ -328,7 +328,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class Location : Object {
+	private sealed class Location : Object {
 		public string executable_name {
 			get;
 			construct;
@@ -988,7 +988,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ScriptRunner : BaseController {
+	private sealed class ScriptRunner : BaseController {
 		private ScriptEngine engine;
 		private Script script;
 
@@ -1036,7 +1036,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ScriptDirectoryRunner : BaseController {
+	private sealed class ScriptDirectoryRunner : BaseController {
 		public string directory_path {
 			get;
 			construct;
@@ -1241,7 +1241,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class Script : Object, RpcPeer {
+	private sealed class Script : Object, RpcPeer {
 		private const uint8 QUICKJS_BYTECODE_MAGIC = 0x02;
 
 		public enum ChangeBehavior {
@@ -1453,7 +1453,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ControlServer : BaseController {
+	private sealed class ControlServer : BaseController {
 		public EndpointParameters endpoint_params {
 			get;
 			construct;
@@ -1694,7 +1694,7 @@ namespace Frida.Gadget {
 			public abstract async void close (Cancellable? cancellable = null) throws IOError;
 		}
 
-		private class AuthenticationChannel : Object, Peer, AuthenticationService {
+		private sealed class AuthenticationChannel : Object, Peer, AuthenticationService {
 			public weak ControlServer parent {
 				get;
 				construct;
@@ -1742,7 +1742,7 @@ namespace Frida.Gadget {
 			}
 		}
 
-		private class ControlChannel : Object, Peer, HostSession {
+		private sealed class ControlChannel : Object, Peer, HostSession {
 			public weak ControlServer parent {
 				get;
 				construct;
@@ -1927,13 +1927,21 @@ namespace Frida.Gadget {
 				throw new Error.NOT_SUPPORTED ("Unable to inject libraries when embedded");
 			}
 
+			public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Unable to open channels when embedded");
+			}
+
+			public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Unable to open services when embedded");
+			}
+
 			private void validate_pid (uint pid) throws Error {
 				if (pid != this_process.pid)
 					throw new Error.NOT_SUPPORTED ("Unable to act on other processes when embedded");
 			}
 		}
 
-		private class LiveAgentSession : BaseAgentSession {
+		private sealed class LiveAgentSession : BaseAgentSession {
 			public ControlChannel? controller {
 				get;
 				set;
@@ -1958,7 +1966,7 @@ namespace Frida.Gadget {
 		}
 	}
 
-	private class ClusterClient : BaseController {
+	private sealed class ClusterClient : BaseController {
 		public SocketConnectable connectable {
 			get;
 			construct;

lib/netif/tunnel-interface-observer.vala

@@ -1,4 +1,4 @@
-public class Frida.TunnelInterfaceObserver : Object, DynamicInterfaceObserver {
+public sealed class Frida.TunnelInterfaceObserver : Object, DynamicInterfaceObserver {
 #if IOS || TVOS
 	private Gee.Map<string, DynamicInterface> interfaces = new Gee.HashMap<string, DynamicInterface> ();
 

lib/payload/cloak.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class ThreadIgnoreScope {
+	public sealed class ThreadIgnoreScope {
 		public enum Kind {
 			APPLICATION_THREAD,
 			FRIDA_THREAD
@@ -43,7 +43,7 @@ namespace Frida {
 	}
 
 #if ANDROID
-	public class ThreadCountCloaker : Object {
+	public sealed class ThreadCountCloaker : Object {
 		private ReadFunc * read_slot;
 		private static ReadFunc old_read_impl;
 
@@ -156,12 +156,12 @@ namespace Frida {
 		}
 	}
 #else
-	public class ThreadCountCloaker : Object {
+	public sealed class ThreadCountCloaker : Object {
 	}
 #endif
 
 #if LINUX
-	public class ThreadListCloaker : Object, DirListFilter {
+	public sealed class ThreadListCloaker : Object, DirListFilter {
 		private string our_dir_by_pid;
 		private DirListCloaker cloaker;
 
@@ -180,7 +180,7 @@ namespace Frida {
 		}
 	}
 
-	public class FDListCloaker : Object, DirListFilter {
+	public sealed class FDListCloaker : Object, DirListFilter {
 		private string our_dir_by_pid;
 		private DirListCloaker cloaker;
 
@@ -199,7 +199,7 @@ namespace Frida {
 		}
 	}
 
-	private class DirListCloaker : Object {
+	private sealed class DirListCloaker : Object {
 		public weak DirListFilter filter {
 			get;
 			construct;
@@ -467,10 +467,10 @@ namespace Frida {
 		public abstract bool matches_file (string name);
 	}
 #else
-	public class ThreadListCloaker : Object {
+	public sealed class ThreadListCloaker : Object {
 	}
 
-	public class FDListCloaker : Object {
+	public sealed class FDListCloaker : Object {
 	}
 #endif
 }

lib/payload/exit-monitor.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class ExitMonitor : Object, Gum.InvocationListener {
+	public sealed class ExitMonitor : Object, Gum.InvocationListener {
 		public weak ExitHandler handler {
 			get;
 			construct;

lib/payload/fd-guard.vala

@@ -1,6 +1,6 @@
 namespace Frida {
 #if WINDOWS
-	public class FileDescriptorGuard : Object {
+	public sealed class FileDescriptorGuard : Object {
 		public Gum.MemoryRange agent_range {
 			get;
 			construct;
@@ -11,7 +11,7 @@ namespace Frida {
 		}
 	}
 #else
-	public class FileDescriptorGuard : Object {
+	public sealed class FileDescriptorGuard : Object {
 		public Gum.MemoryRange agent_range {
 			get;
 			construct;

lib/payload/fdt-padder.vala

@@ -1,6 +1,6 @@
 namespace Frida {
 #if WINDOWS
-	public class FileDescriptorTablePadder {
+	public sealed class FileDescriptorTablePadder {
 		public static FileDescriptorTablePadder obtain () {
 			return new FileDescriptorTablePadder ();
 		}
@@ -9,7 +9,7 @@ namespace Frida {
 		}
 	}
 #else
-	public class FileDescriptorTablePadder {
+	public sealed class FileDescriptorTablePadder {
 		private const int MIN_TABLE_SIZE = 32;
 
 		private static unowned FileDescriptorTablePadder shared_instance = null;

lib/payload/fork-monitor.vala

@@ -1,6 +1,6 @@
 namespace Frida {
 #if WINDOWS
-	public class ForkMonitor : Object {
+	public sealed class ForkMonitor : Object {
 		public weak ForkHandler handler {
 			get;
 			construct;
@@ -11,7 +11,7 @@ namespace Frida {
 		}
 	}
 #else
-	public class ForkMonitor : Object, Gum.InvocationListener {
+	public sealed class ForkMonitor : Object, Gum.InvocationListener {
 		public weak ForkHandler handler {
 			get;
 			construct;

lib/payload/portal-client.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class PortalClient : Object, AgentSessionProvider {
+	public sealed class PortalClient : Object, AgentSessionProvider {
 		public signal void resume ();
 		public signal void kill ();
 

lib/payload/script-engine.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class ScriptEngine : Object {
+	public sealed class ScriptEngine : Object {
 		public signal void message_from_script (AgentScriptId script_id, string json, Bytes? data);
 		public signal void message_from_debugger (AgentScriptId script_id, string message);
 
@@ -223,7 +223,7 @@ namespace Frida {
 			source.attach (Gum.ScriptBackend.get_scheduler ().get_js_context ());
 		}
 
-		public class ScriptInstance : Object, RpcPeer {
+		public sealed class ScriptInstance : Object, RpcPeer {
 			public signal void closed ();
 			public signal void message (string json, Bytes? data);
 			public signal void debug_message (string message);

lib/payload/spawn-monitor.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class SpawnMonitor : Object, Gum.InvocationListener {
+	public sealed class SpawnMonitor : Object, Gum.InvocationListener {
 		public weak SpawnHandler handler {
 			get;
 			construct;

lib/payload/thread-suspend-monitor.vala

@@ -1,6 +1,6 @@
 namespace Frida {
 #if DARWIN
-	public class ThreadSuspendMonitor : Object {
+	public sealed class ThreadSuspendMonitor : Object {
 		public weak ProcessInvader invader {
 			get;
 			construct;
@@ -131,7 +131,7 @@ namespace Frida {
 		}
 	}
 #else
-	public class ThreadSuspendMonitor : Object {
+	public sealed class ThreadSuspendMonitor : Object {
 		public weak ProcessInvader invader {
 			get;
 			construct;

lib/payload/unwind-sitter.vala

@@ -1,6 +1,6 @@
 namespace Frida {
 #if DARWIN
-	public class UnwindSitter : Object {
+	public sealed class UnwindSitter : Object {
 		public weak ProcessInvader invader {
 			get;
 			construct;
@@ -62,7 +62,7 @@ namespace Frida {
 		public extern static void _unhook_libunwind ();
 	}
 #else
-	public class UnwindSitter : Object {
+	public sealed class UnwindSitter : Object {
 		public weak ProcessInvader invader {
 			get;
 			construct;

lib/pipe/pipe.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class PipeTransport : Object {
+	public sealed class PipeTransport : Object {
 		public string local_address {
 			get;
 			construct;
@@ -42,7 +42,7 @@ namespace Frida {
 	}
 
 #if WINDOWS
-	public class WindowsPipe : IOStream {
+	public sealed class WindowsPipe : IOStream {
 		public string address {
 			get;
 			construct;

meson.build

@@ -431,7 +431,6 @@ if gi_dep.found()
 else
   girdir = get_option('prefix') / get_option('datadir') / 'gir-1.0'
 endif
-uninstalled_girdir = meson.current_build_dir() / 'src'
 
 vapidir = get_option('prefix') / get_option('datadir') / 'vala' / 'vapi'
 

portal/portal.vala

@@ -142,7 +142,7 @@ namespace Frida.Portal {
 		return application.run ();
 	}
 
-	private class Application : Object {
+	private sealed class Application : Object {
 		public signal void ready (bool success);
 
 		public PortalService service {

server/server.vala

@@ -235,7 +235,7 @@ namespace Frida.Server {
 	}
 #endif
 
-	private class Application : Object {
+	private sealed class Application : Object {
 		public signal void ready (bool success);
 
 		public string? device_id {

src/agent-container.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class AgentContainer : Object, AgentSessionProvider {
+	public sealed class AgentContainer : Object, AgentSessionProvider {
 		public DBusConnection connection {
 			get;
 			private set;

src/api/generate.py

@@ -20,6 +20,8 @@ CORE_TAG_FIELD = f"{{{CORE_NAMESPACE}}}field"
 CORE_TAG_CONSTRUCTOR = f"{{{CORE_NAMESPACE}}}constructor"
 CORE_TAG_METHOD = f"{{{CORE_NAMESPACE}}}method"
 
+OBJECT_TYPE_PATTERN = re.compile(r"\bpublic\s+(sealed )?(class|interface)\s+(\w+)\b")
+
 def main():
     parser = argparse.ArgumentParser(description="Generate refined Frida API definitions")
     parser.add_argument('--output', dest='output_type', choices=['bundle', 'header', 'gir', 'vapi', 'vapi-stamp'], default='bundle')
@@ -288,12 +290,18 @@ def parse_api(api_version, toplevel_code, core_header, core_vapi, base_header, b
         "StaticAuthenticationService": "AuthenticationService",
     }
     internal_type_prefixes = [
+        "AgentMessageKind",
         "Fruity",
         "HostSession",
         "MessageType",
+        "PeerSetup",
+        "PortConflictBehavior",
         "ResultCode",
         "SpawnStartState",
         "State",
+        "StringTerminator",
+        "UnloadPolicy",
+        "WebService",
         "Winjector"
     ]
     seen_enum_names = set()
@@ -412,8 +420,8 @@ def parse_api(api_version, toplevel_code, core_header, core_vapi, base_header, b
                         current_enum.vapi_declaration = stripped_line
                     else:
                         ignoring = True
-                elif stripped_line.startswith("public class") or stripped_line.startswith("public interface"):
-                    name = re.match(r"^public (class|interface) (\w+) ", stripped_line).group(2)
+                elif (match := OBJECT_TYPE_PATTERN.match(stripped_line)) is not None:
+                    name = match.group(3)
                     if name not in object_type_by_name:
                         ignoring = True
                     else:
@@ -470,7 +478,7 @@ def function_is_public(name):
             ]
 
 def parse_vala_object_types(source) -> List[ApiObjectType]:
-    return [ApiObjectType(m.group(2), m.group(1)) for m in re.finditer(r"^\t+public\s+(class|interface)\s+(\w+)\s+", source, re.MULTILINE)]
+    return [ApiObjectType(m.group(3), m.group(2)) for m in OBJECT_TYPE_PATTERN.finditer(source, re.MULTILINE)]
 
 def parse_vapi_functions(vapi) -> List[ApiFunction]:
     return [ApiFunction(m.group(1), m.group(0)) for m in re.finditer(r"^\tpublic static .+ (\w+) \(.+;", vapi, re.MULTILINE)]

src/api/meson.build

@@ -1,3 +1,5 @@
+fs = import('fs')
+
 generate_api = [python, files('generate.py')]
 
 generate_api_args = [
@@ -32,6 +34,8 @@ core_public_h = core_api[0]
 core_public_gir = core_api[1]
 core_public_vapi = [core_api[2], core_api[3]]
 
+gio_gir = fs.copyfile('Gio-2.0.gir')
+
 core_public_vapi_stamp = custom_target('frida-core-vapi-stamp',
   input: core_public_vapi,
   output: f'frida-core-@[email protected]',
@@ -59,8 +63,6 @@ core_public_lib = custom_target('frida-core-library',
   install_dir: get_option('libdir'),
 )
 
-fs = import('fs')
-
 core_public_extra_headers = []
 if host_os == 'android'
   core_public_extra_headers += fs.copyfile(frida_selinux_h)
@@ -71,6 +73,7 @@ if build_machine.system() == 'windows'
 else
   uninstalled_incdir = meson.current_build_dir()
 endif
+uninstalled_girdir = uninstalled_incdir
 uninstalled_vapidir = uninstalled_incdir
 
 uninstalled_variables = {
@@ -86,7 +89,7 @@ installed_variables = {
 }
 
 core_public_dep = declare_dependency(
-  sources: [core_public_h, core_public_gir, core_public_vapi_stamp, core_public_extra_headers],
+  sources: [core_public_h, core_public_gir, gio_gir, core_public_vapi_stamp, core_public_extra_headers],
   include_directories: include_directories('.'),
   link_args: backend_libs_private,
   link_with: core_public_lib,

src/barebone/allocator.vala

@@ -17,7 +17,7 @@ namespace Frida.Barebone {
 		public abstract async void deallocate (Cancellable? cancellable) throws Error, IOError;
 	}
 
-	public class SimpleAllocator : Object, Allocator {
+	public sealed class SimpleAllocator : Object, Allocator {
 		public size_t page_size {
 			get { return _page_size; }
 		}

src/barebone/arch-arm/machine.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class ArmMachine : Object, Machine {
+	public sealed class ArmMachine : Object, Machine {
 		public override GDB.Client gdb {
 			get;
 			set;

src/barebone/arch-arm64/machine.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class Arm64Machine : Object, Machine {
+	public sealed class Arm64Machine : Object, Machine {
 		public override GDB.Client gdb {
 			get;
 			set;

src/barebone/arch-unknown/machine.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class UnknownMachine : Object, Machine {
+	public sealed class UnknownMachine : Object, Machine {
 		public GDB.Client gdb {
 			get;
 			set;

src/barebone/arch-x86/machine.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class IA32Machine : Object, Machine {
+	public sealed class IA32Machine : Object, Machine {
 		public override GDB.Client gdb {
 			get;
 			set;

src/barebone/arch-x86_64/machine.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class X64Machine : Object, Machine {
+	public sealed class X64Machine : Object, Machine {
 		public override GDB.Client gdb {
 			get;
 			set;

src/barebone/barebone-host-session.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class BareboneHostSessionBackend : Object, HostSessionBackend {
+	public sealed class BareboneHostSessionBackend : Object, HostSessionBackend {
 		private BareboneHostSessionProvider? provider;
 
 		private const uint16 DEFAULT_PORT = 3333;
@@ -30,7 +30,7 @@ namespace Frida {
 		}
 	}
 
-	public class BareboneHostSessionProvider : Object, HostSessionProvider {
+	public sealed class BareboneHostSessionProvider : Object, HostSessionProvider {
 		public string id {
 			get { return "barebone"; }
 		}
@@ -141,12 +141,35 @@ namespace Frida {
 			return yield this.host_session.link_agent_session (id, sink, cancellable);
 		}
 
+		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_agent_session (id);
+		}
+
+		public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+				throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+		}
+
+		public void unlink_channel (HostSession host_session, ChannelId id) {
+		}
+
+		public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id, Cancellable? cancellable)
+				throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
+		public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+		}
+
 		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
 			agent_session_detached (id, reason, crash);
 		}
 	}
 
-	public class BareboneHostSession : Object, HostSession {
+	public sealed class BareboneHostSession : Object, HostSession {
 		public Barebone.Services services {
 			get;
 			construct;
@@ -260,6 +283,14 @@ namespace Frida {
 			return session;
 		}
 
+		public void unlink_agent_session (AgentSessionId id) {
+			BareboneAgentSession? session = agent_sessions[id];
+			if (session == null)
+				return;
+
+			session.message_sink = null;
+		}
+
 		public async InjectorPayloadId inject_library_file (uint pid, string path, string entrypoint, string data,
 				Cancellable? cancellable) throws Error, IOError {
 			throw_not_supported ();
@@ -270,6 +301,14 @@ namespace Frida {
 			throw_not_supported ();
 		}
 
+		public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+		}
+
+		public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
 		private void on_agent_session_closed (BareboneAgentSession session) {
 			AgentSessionId id = session.id;
 
@@ -282,7 +321,7 @@ namespace Frida {
 		}
 	}
 
-	private class BareboneAgentSession : Object, AgentSession {
+	private sealed class BareboneAgentSession : Object, AgentSession {
 		public signal void closed ();
 
 		public AgentSessionId id {
@@ -525,7 +564,7 @@ namespace Frida {
 	}
 
 	namespace Barebone {
-		public class Services : Object {
+		public sealed class Services : Object {
 			public Machine machine {
 				get;
 				construct;

src/barebone/callback.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class Callback : Object {
+	public sealed class Callback : Object {
 		private uint64 code;
 		private CallbackHandler handler;
 		private Machine machine;

src/barebone/interceptor.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	public class Interceptor : Object {
+	public sealed class Interceptor : Object {
 		public Machine machine {
 			get;
 			construct;

src/barebone/rust-module.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaBarebone", gir_version = "1.0")]
 namespace Frida.Barebone {
-	private class RustModule : Object {
+	private sealed class RustModule : Object {
 		public signal void console_output (string message);
 
 		public Gee.List<Export> exports {

src/barebone/script.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	private class BareboneScript : Object {
+	private sealed class BareboneScript : Object {
 		public signal void message (string json, Bytes? data);
 
 		public AgentScriptId id {

src/compiler/compiler.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class Compiler : Object {
+	public sealed class Compiler : Object {
 		public signal void starting ();
 		public signal void finished ();
 		public signal void output (string bundle);
@@ -199,7 +199,7 @@ namespace Frida {
 			try {
 				var device = yield manager.get_device_by_type (LOCAL, 0, io_cancellable);
 				var session = yield device.get_host_session (io_cancellable);
-				var agent = new Agent (this, (BaseDBusHostSession) session);
+				var agent = new Agent (this, (LocalHostSession) session);
 
 				load_request.resolve (agent);
 			} catch (GLib.Error e) {
@@ -238,7 +238,7 @@ namespace Frida {
 			private Promise<string> source_request = new Promise<string> ();
 			private Promise<Bytes?> snapshot_request = new Promise<Bytes?> ();
 
-			public Agent (Compiler parent, BaseDBusHostSession host_session) {
+			public Agent (Compiler parent, LocalHostSession host_session) {
 				Object (
 					parent: parent,
 					host_session: host_session,
@@ -465,10 +465,10 @@ namespace Frida {
 		}
 	}
 
-	public class BuildOptions : CompilerOptions {
+	public sealed class BuildOptions : CompilerOptions {
 	}
 
-	public class WatchOptions : CompilerOptions {
+	public sealed class WatchOptions : CompilerOptions {
 	}
 
 	public enum SourceMaps {

src/compiler/package-lock.json

@@ -9,7 +9,7 @@
       "version": "1.0.0",
       "dependencies": {
         "@frida/crosspath": "3.0.0",
-        "frida-compile": "16.4.1",
+        "frida-compile": "16.4.2",
         "frida-fs": "5.2.5"
       },
       "devDependencies": {
@@ -17,7 +17,7 @@
         "@rollup/plugin-node-resolve": "^14.1.0",
         "@rollup/plugin-replace": "^4.0.0",
         "@rollup/plugin-typescript": "^8.3.4",
-        "@types/frida-gum": "18.8.1",
+        "@types/frida-gum": "18.8.2",
         "@types/glob": "^8.0.0",
         "@types/node": "18.7.23",
         "glob": "^8.0.3",
@@ -468,9 +468,9 @@
       "dev": true
     },
     "node_modules/@types/frida-gum": {
-      "version": "18.8.1",
-      "resolved": "https://registry.npmjs.org/@types/frida-gum/-/frida-gum-18.8.1.tgz",
-      "integrity": "sha512-FhlHORjaw43QbNYIyj5Ji7iYSvk7t5nPiC+GuYDVndqc1bFheeAs88b1odp8HhmpQUrrYVU90wapapKVLlmJHg==",
+      "version": "18.8.2",
+      "resolved": "https://registry.npmjs.org/@types/frida-gum/-/frida-gum-18.8.2.tgz",
+      "integrity": "sha512-5KH6ITrKJQe1UWrNnbXXx3KXRe/Lx9I1EwkBdC+AMmlo9F5UC0PxdC959aGxhfjXBRIHWxXwXPi3JmeWIbeqeg==",
       "dev": true,
       "license": "MIT"
     },
@@ -641,9 +641,9 @@
       "dev": true
     },
     "node_modules/frida-compile": {
-      "version": "16.4.1",
-      "resolved": "https://registry.npmjs.org/frida-compile/-/frida-compile-16.4.1.tgz",
-      "integrity": "sha512-xI9HNtUFpHxuKBGXaL6XJAYH1zWTvNJDrHRnz1hp0oS24iPHt6c01Jmm3qljZek3oQWn8HhvfNvrzfgbsKzoBQ==",
+      "version": "16.4.2",
+      "resolved": "https://registry.npmjs.org/frida-compile/-/frida-compile-16.4.2.tgz",
+      "integrity": "sha512-wNiFk37JVpCoEsuJF9AHZtccM9Z3KGj3yu0Amsb/DKzKnHCxvl8AlAU5qSfYXfAJtzbNuCKGqNBM8u96KvP28A==",
       "dependencies": {
         "@frida/assert": "^3.0.1",
         "@frida/base64-js": "^2.0.3",
@@ -1466,9 +1466,9 @@
       "dev": true
     },
     "@types/frida-gum": {
-      "version": "18.8.1",
-      "resolved": "https://registry.npmjs.org/@types/frida-gum/-/frida-gum-18.8.1.tgz",
-      "integrity": "sha512-FhlHORjaw43QbNYIyj5Ji7iYSvk7t5nPiC+GuYDVndqc1bFheeAs88b1odp8HhmpQUrrYVU90wapapKVLlmJHg==",
+      "version": "18.8.2",
+      "resolved": "https://registry.npmjs.org/@types/frida-gum/-/frida-gum-18.8.2.tgz",
+      "integrity": "sha512-5KH6ITrKJQe1UWrNnbXXx3KXRe/Lx9I1EwkBdC+AMmlo9F5UC0PxdC959aGxhfjXBRIHWxXwXPi3JmeWIbeqeg==",
       "dev": true
     },
     "@types/glob": {
@@ -1597,9 +1597,9 @@
       "dev": true
     },
     "frida-compile": {
-      "version": "16.4.1",
-      "resolved": "https://registry.npmjs.org/frida-compile/-/frida-compile-16.4.1.tgz",
-      "integrity": "sha512-xI9HNtUFpHxuKBGXaL6XJAYH1zWTvNJDrHRnz1hp0oS24iPHt6c01Jmm3qljZek3oQWn8HhvfNvrzfgbsKzoBQ==",
+      "version": "16.4.2",
+      "resolved": "https://registry.npmjs.org/frida-compile/-/frida-compile-16.4.2.tgz",
+      "integrity": "sha512-wNiFk37JVpCoEsuJF9AHZtccM9Z3KGj3yu0Amsb/DKzKnHCxvl8AlAU5qSfYXfAJtzbNuCKGqNBM8u96KvP28A==",
       "requires": {
         "@frida/assert": "^3.0.1",
         "@frida/base64-js": "^2.0.3",

src/compiler/package.json

@@ -9,7 +9,7 @@
   },
   "dependencies": {
     "@frida/crosspath": "3.0.0",
-    "frida-compile": "16.4.1",
+    "frida-compile": "16.4.2",
     "frida-fs": "5.2.5"
   },
   "devDependencies": {
@@ -17,7 +17,7 @@
     "@rollup/plugin-node-resolve": "^14.1.0",
     "@rollup/plugin-replace": "^4.0.0",
     "@rollup/plugin-typescript": "^8.3.4",
-    "@types/frida-gum": "18.8.1",
+    "@types/frida-gum": "18.8.2",
     "@types/glob": "^8.0.0",
     "@types/node": "18.7.23",
     "glob": "^8.0.3",

src/control-service.vala

@@ -1,6 +1,5 @@
 namespace Frida {
-#if HAVE_LOCAL_BACKEND
-	public class ControlService : Object {
+	public sealed class ControlService : Object {
 		public EndpointParameters endpoint_params {
 			get;
 			construct;
@@ -12,6 +11,7 @@ namespace Frida {
 		}
 
 		private HostSession host_session;
+		private HostSessionProvider provider;
 
 		private State state = STOPPED;
 
@@ -21,8 +21,12 @@ namespace Frida {
 
 		private Gee.Set<ControlChannel> spawn_gaters = new Gee.HashSet<ControlChannel> ();
 		private Gee.Map<uint, PendingSpawn> pending_spawn = new Gee.HashMap<uint, PendingSpawn> ();
-		private Gee.Map<AgentSessionId?, AgentSessionEntry> sessions =
+		private Gee.Map<AgentSessionId?, AgentSessionEntry> agent_sessions =
 			new Gee.HashMap<AgentSessionId?, AgentSessionEntry> (AgentSessionId.hash, AgentSessionId.equal);
+		private Gee.Map<ChannelId?, ChannelEntry> channels =
+			new Gee.HashMap<ChannelId?, ChannelEntry> (ChannelId.hash, ChannelId.equal);
+		private Gee.Map<ServiceSessionId?, ServiceSessionEntry> service_sessions =
+			new Gee.HashMap<ServiceSessionId?, ServiceSessionEntry> (ServiceSessionId.hash, ServiceSessionId.equal);
 
 		private Cancellable io_cancellable = new Cancellable ();
 
@@ -35,7 +39,8 @@ namespace Frida {
 			STOPPING
 		}
 
-		public ControlService (EndpointParameters endpoint_params, ControlServiceOptions? options = null) {
+		public ControlService (EndpointParameters endpoint_params, ControlServiceOptions? options = null) throws Error {
+#if HAVE_LOCAL_BACKEND
 			ControlServiceOptions opts = (options != null) ? options : new ControlServiceOptions ();
 
 			HostSession session;
@@ -63,7 +68,10 @@ namespace Frida {
 				options: opts
 			);
 
-			assign_session (session);
+			assign_session (session, new PrecreatedLocalHostSessionProvider ((LocalHostSession) session));
+#else
+			throw new Error.NOT_SUPPORTED ("Local backend not available");
+#endif
 		}
 
 		public async ControlService.with_device (Device device, EndpointParameters endpoint_params,
@@ -77,17 +85,7 @@ namespace Frida {
 				options: opts
 			);
 
-			assign_session (session);
-		}
-
-		internal ControlService.with_host_session (HostSession host_session, EndpointParameters endpoint_params,
-				ControlServiceOptions? options = null) {
-			Object (
-				endpoint_params: endpoint_params,
-				options: (options != null) ? options : new ControlServiceOptions ()
-			);
-
-			assign_session (host_session);
+			assign_session (session, device.provider);
 		}
 
 		construct {
@@ -99,7 +97,7 @@ namespace Frida {
 			main_handler = new ConnectionHandler (this, null);
 		}
 
-		private void assign_session (HostSession session) {
+		private void assign_session (HostSession session, HostSessionProvider provider) {
 			host_session = session;
 			host_session.spawn_added.connect (notify_spawn_added);
 			host_session.child_added.connect (notify_child_added);
@@ -107,7 +105,11 @@ namespace Frida {
 			host_session.process_crashed.connect (notify_process_crashed);
 			host_session.output.connect (notify_output);
 			host_session.agent_session_detached.connect (on_agent_session_detached);
+			host_session.channel_closed.connect (on_channel_closed);
+			host_session.service_session_closed.connect (on_service_session_closed);
 			host_session.uninjected.connect (notify_uninjected);
+
+			this.provider = provider;
 		}
 
 		public async void start (Cancellable? cancellable = null) throws Error, IOError {
@@ -123,7 +125,7 @@ namespace Frida {
 				yield service.start (cancellable);
 
 				if (options.enable_preload) {
-					var base_host_session = host_session as BaseDBusHostSession;
+					var base_host_session = host_session as LocalHostSession;
 					if (base_host_session != null)
 						base_host_session.preload.begin (io_cancellable);
 				}
@@ -162,9 +164,8 @@ namespace Frida {
 
 			yield main_handler.close (cancellable);
 
-			var base_host_session = host_session as BaseDBusHostSession;
-			if (base_host_session != null)
-				yield base_host_session.close (cancellable);
+			if (provider is PrecreatedLocalHostSessionProvider)
+				yield provider.destroy (host_session, cancellable);
 
 			state = STOPPED;
 		}
@@ -226,17 +227,15 @@ namespace Frida {
 		}
 
 		private async void teardown_control_channel (ControlChannel channel) {
-			foreach (AgentSessionId id in channel.sessions) {
-				AgentSessionEntry entry = sessions[id];
+			foreach (AgentSessionId id in channel.agent_sessions) {
+				AgentSessionEntry entry = agent_sessions[id];
 
-				var base_host_session = host_session as BaseDBusHostSession;
-				if (base_host_session != null)
-					base_host_session.unlink_agent_session (id);
+				provider.unlink_agent_session (host_session, id);
 
 				AgentSession? session = entry.session;
 
 				if (entry.persist_timeout == 0 || session == null) {
-					sessions.unset (id);
+					agent_sessions.unset (id);
 					if (session != null)
 						session.close.begin (io_cancellable);
 				} else {
@@ -245,6 +244,24 @@ namespace Frida {
 				}
 			}
 
+			foreach (ChannelId id in channel.channels.to_array ()) {
+				ChannelEntry entry = channels[id];
+
+				provider.unlink_channel (host_session, id);
+
+				channels.unset (id);
+
+				Channel? ch = entry.channel;
+				if (ch != null)
+					ch.close.begin (null);
+			}
+
+			foreach (ServiceSessionId id in channel.service_sessions.to_array ()) {
+				provider.unlink_service_session (host_session, id);
+
+				service_sessions.unset (id);
+			}
+
 			try {
 				yield disable_spawn_gating (channel);
 			} catch (GLib.Error e) {
@@ -379,12 +396,22 @@ namespace Frida {
 				yield parent.reattach (id, requester, cancellable);
 			}
 
+			public async ChannelId open_channel (string address, ControlChannel requester, Cancellable? cancellable)
+					throws Error, IOError {
+				return yield parent.open_channel (address, requester, cancellable);
+			}
+
+			public async ServiceSessionId open_service (string address, ControlChannel requester, Cancellable? cancellable)
+					throws Error, IOError {
+				return yield parent.open_service (address, requester, cancellable);
+			}
+
 			public void open_tcp_transport (AgentSessionId id, Cancellable? cancellable, out uint16 port, out string token)
 					throws Error {
 #if WINDOWS
 				throw new Error.NOT_SUPPORTED ("Not yet supported on Windows");
 #else
-				var base_host_session = host_session as BaseDBusHostSession;
+				var base_host_session = host_session as LocalHostSession;
 				if (base_host_session == null)
 					throw new Error.NOT_SUPPORTED ("Not supported for remote host sessions");
 				if (!base_host_session.can_pass_file_descriptors_to_agent_session (id))
@@ -454,7 +481,7 @@ namespace Frida {
 #if !WINDOWS
 				AgentSessionId session_id = transport.session_id;
 
-				var base_host_session = host_session as BaseDBusHostSession;
+				var base_host_session = host_session as LocalHostSession;
 				if (base_host_session == null)
 					throw new Error.NOT_SUPPORTED ("Not supported for remote host sessions");
 
@@ -537,12 +564,12 @@ namespace Frida {
 				throw_dbus_error (e);
 			}
 
-			requester.sessions.add (id);
+			requester.agent_sessions.add (id);
 
 			var opts = SessionOptions._deserialize (options);
 
-			var entry = new AgentSessionEntry (requester, id, opts.persist_timeout, io_cancellable);
-			sessions[id] = entry;
+			var entry = new AgentSessionEntry (requester, id, opts.persist_timeout);
+			agent_sessions[id] = entry;
 			entry.expired.connect (on_agent_session_expired);
 
 			yield link_session (id, entry, requester, cancellable);
@@ -551,11 +578,11 @@ namespace Frida {
 		}
 
 		private async void reattach (AgentSessionId id, ControlChannel requester, Cancellable? cancellable) throws Error, IOError {
-			AgentSessionEntry? entry = sessions[id];
+			AgentSessionEntry? entry = agent_sessions[id];
 			if (entry == null || entry.controller != null)
 				throw new Error.INVALID_OPERATION ("Invalid session ID");
 
-			requester.sessions.add (id);
+			requester.agent_sessions.add (id);
 
 			entry.attach_controller (requester);
 
@@ -574,28 +601,7 @@ namespace Frida {
 				throw_dbus_error (e);
 			}
 
-			AgentSession session;
-			var base_host_session = host_session as BaseDBusHostSession;
-			if (base_host_session != null) {
-				session = yield base_host_session.link_agent_session (id, sink, cancellable);
-			} else {
-				DBusConnection internal_connection = ((DBusProxy) host_session).g_connection;
-
-				try {
-					session = yield internal_connection.get_proxy (null, ObjectPath.for_agent_session (id),
-						DO_NOT_LOAD_PROPERTIES, cancellable);
-				} catch (IOError e) {
-					throw_dbus_error (e);
-				}
-
-				entry.internal_connection = internal_connection;
-				try {
-					entry.take_internal_registration (
-						internal_connection.register_object (ObjectPath.for_agent_message_sink (id), sink));
-				} catch (IOError e) {
-					assert_not_reached ();
-				}
-			}
+			var session = yield provider.link_agent_session (host_session, id, sink, cancellable);
 
 			entry.session = session;
 			try {
@@ -606,6 +612,52 @@ namespace Frida {
 			}
 		}
 
+		private async ChannelId open_channel (string address, ControlChannel requester, Cancellable? cancellable)
+				throws Error, IOError {
+			ChannelId id;
+			try {
+				id = yield host_session.open_channel (address, cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
+
+			requester.channels.add (id);
+
+			var entry = new ChannelEntry (requester, id);
+			channels[id] = entry;
+
+			var stream = yield provider.link_channel (host_session, id, cancellable);
+
+			Channel channel = new ChannelEndpoint (stream);
+			entry.channel = channel;
+			entry.take_controller_registration (requester.connection.register_object (ObjectPath.for_channel (id), channel));
+
+			return id;
+		}
+
+		private async ServiceSessionId open_service (string address, ControlChannel requester, Cancellable? cancellable)
+				throws Error, IOError {
+			ServiceSessionId id;
+			try {
+				id = yield host_session.open_service (address, cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
+
+			requester.service_sessions.add (id);
+
+			var entry = new ServiceSessionEntry (requester, id);
+			service_sessions[id] = entry;
+
+			var session = yield provider.link_service_session (host_session, id, cancellable);
+
+			entry.session = session;
+			entry.take_controller_registration (
+				requester.connection.register_object (ObjectPath.for_service_session (id), session));
+
+			return id;
+		}
+
 		private void notify_spawn_added (HostSpawnInfo info) {
 			foreach (ControlChannel channel in spawn_gaters)
 				channel.spawn_added (info);
@@ -646,15 +698,33 @@ namespace Frida {
 
 		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
 			AgentSessionEntry entry;
-			if (sessions.unset (id, out entry)) {
+			if (agent_sessions.unset (id, out entry)) {
 				ControlChannel? controller = entry.controller;
 				if (controller != null) {
-					controller.sessions.remove (id);
+					controller.agent_sessions.remove (id);
 					controller.agent_session_detached (id, reason, crash);
 				}
 			}
 		}
 
+		private void on_channel_closed (ChannelId id) {
+			ChannelEntry entry;
+			if (channels.unset (id, out entry)) {
+				ControlChannel controller = entry.controller;
+				controller.channels.remove (id);
+				controller.channel_closed (id);
+			}
+		}
+
+		private void on_service_session_closed (ServiceSessionId id) {
+			ServiceSessionEntry entry;
+			if (service_sessions.unset (id, out entry)) {
+				ControlChannel controller = entry.controller;
+				controller.service_sessions.remove (id);
+				controller.service_session_closed (id);
+			}
+		}
+
 		private void notify_uninjected (InjectorPayloadId id) {
 			all_control_channels ().foreach (channel => {
 				channel.uninjected (id);
@@ -663,7 +733,7 @@ namespace Frida {
 		}
 
 		private void on_agent_session_expired (AgentSessionEntry entry) {
-			sessions.unset (entry.id);
+			agent_sessions.unset (entry.id);
 		}
 
 		private interface Peer : Object {
@@ -738,11 +808,21 @@ namespace Frida {
 				construct;
 			}
 
-			public Gee.Set<AgentSessionId?> sessions {
+			public Gee.Set<AgentSessionId?> agent_sessions {
 				get;
 				default = new Gee.HashSet<AgentSessionId?> (AgentSessionId.hash, AgentSessionId.equal);
 			}
 
+			public Gee.Set<ChannelId?> channels {
+				get;
+				default = new Gee.HashSet<ChannelId?> (ChannelId.hash, ChannelId.equal);
+			}
+
+			public Gee.Set<ServiceSessionId?> service_sessions {
+				get;
+				default = new Gee.HashSet<ServiceSessionId?> (ServiceSessionId.hash, ServiceSessionId.equal);
+			}
+
 			private Gee.Set<uint> registrations = new Gee.HashSet<uint> ();
 			private TimeoutSource? ping_timer;
 
@@ -867,6 +947,14 @@ namespace Frida {
 				return yield parent.host_session.inject_library_blob (pid, blob, entrypoint, data, cancellable);
 			}
 
+			public async ChannelId open_channel (string address, Cancellable? cancellable) throws GLib.Error {
+				return yield parent.open_channel (address, this, cancellable);
+			}
+
+			public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws GLib.Error {
+				return yield parent.open_service (address, this, cancellable);
+			}
+
 			private async void open_tcp_transport (AgentSessionId id, Cancellable? cancellable, out uint16 port,
 					out string token) throws Error {
 				parent.open_tcp_transport (id, cancellable, out port, out token);
@@ -890,14 +978,45 @@ namespace Frida {
 			}
 		}
 
-		private class AgentSessionEntry {
-			public signal void expired ();
-
+		private abstract class Entry {
 			public ControlChannel? controller {
-				get;
-				private set;
+				get {
+					return _controller;
+				}
+				protected set {
+					unregister_all ();
+					_controller = value;
+				}
 			}
 
+			private ControlChannel? _controller;
+			private Gee.Collection<uint> registrations = new Gee.ArrayList<uint> ();
+
+			protected Entry (ControlChannel? controller) {
+				this.controller = controller;
+			}
+
+			~Entry () {
+				unregister_all ();
+			}
+
+			public void take_controller_registration (uint id) {
+				registrations.add (id);
+			}
+
+			private void unregister_all () {
+				if (_controller == null)
+					return;
+				var connection = _controller.connection;
+				foreach (uint id in registrations)
+					connection.unregister_object (id);
+				registrations.clear ();
+			}
+		}
+
+		private class AgentSessionEntry : Entry {
+			public signal void expired ();
+
 			public AgentSessionId id {
 				get;
 				private set;
@@ -913,36 +1032,20 @@ namespace Frida {
 				private set;
 			}
 
-			public DBusConnection? internal_connection {
-				get;
-				set;
-			}
-
-			public Cancellable io_cancellable {
-				get;
-				private set;
-			}
-
-			private Gee.Collection<uint> internal_registrations = new Gee.ArrayList<uint> ();
-			private Gee.Collection<uint> controller_registrations = new Gee.ArrayList<uint> ();
-
 			private TimeoutSource? expiry_timer;
 
-			public AgentSessionEntry (ControlChannel controller, AgentSessionId id, uint persist_timeout,
-					Cancellable io_cancellable) {
-				this.controller = controller;
+			public AgentSessionEntry (ControlChannel? controller, AgentSessionId id, uint persist_timeout) {
+				base (controller);
+
 				this.id = id;
 				this.persist_timeout = persist_timeout;
-				this.io_cancellable = io_cancellable;
 			}
 
 			~AgentSessionEntry () {
 				stop_expiry_timer ();
-				unregister_all ();
 			}
 
 			public void detach_controller () {
-				unregister_all ();
 				controller = null;
 				session = null;
 
@@ -956,27 +1059,6 @@ namespace Frida {
 				controller = c;
 			}
 
-			public void take_internal_registration (uint id) {
-				internal_registrations.add (id);
-			}
-
-			public void take_controller_registration (uint id) {
-				controller_registrations.add (id);
-			}
-
-			private void unregister_all () {
-				if (controller != null)
-					unregister_all_in (controller_registrations, controller.connection);
-				if (internal_connection != null)
-					unregister_all_in (internal_registrations, internal_connection);
-			}
-
-			private void unregister_all_in (Gee.Collection<uint> ids, DBusConnection connection) {
-				foreach (uint id in ids)
-					connection.unregister_object (id);
-				ids.clear ();
-			}
-
 			private void start_expiry_timer () {
 				if (expiry_timer != null)
 					return;
@@ -995,57 +1077,55 @@ namespace Frida {
 				expiry_timer = null;
 			}
 		}
-	}
-#else
-	public class ControlService : Object {
-		public ControlService (EndpointParameters endpoint_params, ControlServiceOptions? options = null) {
-		}
 
-		public ControlService.with_host_session (HostSession host_session, EndpointParameters endpoint_params,
-				ControlServiceOptions? options = null) {
-		}
-
-		public async void start (Cancellable? cancellable = null) throws Error, IOError {
-			throw new Error.NOT_SUPPORTED ("Local backend not available");
-		}
-
-		public void start_sync (Cancellable? cancellable = null) throws Error, IOError {
-			create<StartTask> ().execute (cancellable);
-		}
-
-		private class StartTask : ControlServiceTask<void> {
-			protected override async void perform_operation () throws Error, IOError {
-				yield parent.start (cancellable);
-			}
-		}
-
-		public async void stop (Cancellable? cancellable = null) throws Error, IOError {
-		}
-
-		public void stop_sync (Cancellable? cancellable = null) throws Error, IOError {
-			create<StopTask> ().execute (cancellable);
-		}
-
-		private class StopTask : ControlServiceTask<void> {
-			protected override async void perform_operation () throws Error, IOError {
-				yield parent.stop (cancellable);
-			}
-		}
-
-		private T create<T> () {
-			return Object.new (typeof (T), parent: this);
-		}
-
-		private abstract class ControlServiceTask<T> : AsyncTask<T> {
-			public weak ControlService parent {
+		private class ChannelEntry : Entry {
+			public ChannelId id {
 				get;
-				construct;
+				private set;
+			}
+
+			public Channel? channel {
+				get;
+				set;
+			}
+
+			public ChannelEntry (ControlChannel controller, ChannelId id) {
+				base (controller);
+
+				this.id = id;
+			}
+		}
+
+		private class ServiceSessionEntry : Entry {
+			public ServiceSessionId id {
+				get;
+				private set;
+			}
+
+			public ServiceSession? session {
+				get;
+				set;
+			}
+
+			public ServiceSessionEntry (ControlChannel controller, ServiceSessionId id) {
+				base (controller);
+
+				this.id = id;
 			}
 		}
 	}
-#endif
 
-	public class ControlServiceOptions : Object {
+	private sealed class PrecreatedLocalHostSessionProvider : LocalHostSessionProvider {
+		public PrecreatedLocalHostSessionProvider (LocalHostSession session) {
+			take_host_session (session);
+		}
+
+		protected override LocalHostSession make_host_session (HostSessionOptions? options) throws Error {
+			throw new Error.NOT_SUPPORTED ("Not supported");
+		}
+	}
+
+	public sealed class ControlServiceOptions : Object {
 		public string? sysroot {
 			get;
 			set;

src/darwin/darwin-host-session.vala

@@ -1,98 +1,24 @@
 namespace Frida {
-	public class DarwinHostSessionBackend : Object, HostSessionBackend {
-		private DarwinHostSessionProvider local_provider;
-
-		public async void start (Cancellable? cancellable) throws IOError {
-			assert (local_provider == null);
-			local_provider = new DarwinHostSessionProvider ();
-			provider_available (local_provider);
-		}
-
-		public async void stop (Cancellable? cancellable) throws IOError {
-			assert (local_provider != null);
-			provider_unavailable (local_provider);
-			yield local_provider.close (cancellable);
-			local_provider = null;
+	public sealed class DarwinHostSessionBackend : LocalHostSessionBackend {
+		protected override LocalHostSessionProvider make_provider () {
+			return new DarwinHostSessionProvider ();
 		}
 	}
 
-	public class DarwinHostSessionProvider : Object, HostSessionProvider {
-		public string id {
-			get { return "local"; }
-		}
-
-		public string name {
-			get { return "Local System"; }
-		}
-
-		public Variant? icon {
-			get { return _icon; }
-		}
-		private Variant? _icon;
-
-		public HostSessionProviderKind kind {
-			get { return HostSessionProviderKind.LOCAL; }
-		}
-
-		private DarwinHostSession host_session;
-
-		construct {
-			_icon = _try_extract_icon ();
-		}
-
-		public async void close (Cancellable? cancellable) throws IOError {
-			if (host_session == null)
-				return;
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async HostSession create (HostSessionOptions? options, Cancellable? cancellable) throws Error, IOError {
-			if (host_session != null)
-				throw new Error.INVALID_OPERATION ("Already created");
-
+	public sealed class DarwinHostSessionProvider : LocalHostSessionProvider {
+		protected override LocalHostSession make_host_session (HostSessionOptions? options) throws Error {
 			var tempdir = new TemporaryDirectory ();
-
-			host_session = new DarwinHostSession (new DarwinHelperProcess (tempdir), tempdir);
-			host_session.agent_session_detached.connect (on_agent_session_detached);
-
-			return host_session;
+			return new DarwinHostSession (new DarwinHelperProcess (tempdir), tempdir);
 		}
 
-		public async void destroy (HostSession session, Cancellable? cancellable) throws Error, IOError {
-			if (session != host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
-				Cancellable? cancellable) throws Error, IOError {
-			if (host_session != this.host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			return yield this.host_session.link_agent_session (id, sink, cancellable);
-		}
-
-		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
-			if (host_session != this.host_session)
-				return;
-
-			this.host_session.unlink_agent_session (id);
-		}
-
-		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
-			agent_session_detached (id, reason, crash);
+		protected override Variant? load_icon () {
+			return _try_extract_icon ();
 		}
 
 		public extern static Variant? _try_extract_icon ();
 	}
 
-	public class DarwinHostSession : BaseDBusHostSession {
+	public sealed class DarwinHostSession : LocalHostSession {
 		public DarwinHelper helper {
 			get;
 			construct;
@@ -410,7 +336,7 @@ namespace Frida {
 	}
 
 #if IOS || TVOS
-	private class FruitController : Object, MappedAgentContainer {
+	private sealed class FruitController : Object, MappedAgentContainer {
 		public signal void spawn_added (HostSpawnInfo info);
 		public signal void spawn_removed (HostSpawnInfo info);
 		public signal void process_crashed (CrashInfo crash);
@@ -815,7 +741,7 @@ namespace Frida {
 			crash_deliveries.unset (delivery.pid);
 		}
 
-		private class CrashDelivery : Object {
+		private sealed class CrashDelivery : Object {
 			public signal void expired ();
 
 			public uint pid {
@@ -882,7 +808,7 @@ namespace Frida {
 
 	private delegate void FoundMappedAgentFunc (MappedAgent agent);
 
-	private class MappedAgent {
+	private sealed class MappedAgent {
 		public uint id {
 			get;
 			private set;
@@ -905,7 +831,7 @@ namespace Frida {
 		}
 	}
 
-	private class LaunchdAgent : InternalAgent {
+	private sealed class LaunchdAgent : InternalAgent {
 		public signal void app_launch_started (string identifier, uint pid);
 		public signal void app_launch_completed (string identifier, uint pid, GLib.Error? error);
 		public signal void spawn_preparation_started (HostSpawnInfo info);
@@ -1015,7 +941,7 @@ namespace Frida {
 		}
 	}
 
-	private class XpcProxyAgent : InternalAgent {
+	private sealed class XpcProxyAgent : InternalAgent {
 		public string identifier {
 			get;
 			construct;
@@ -1057,7 +983,7 @@ namespace Frida {
 		}
 	}
 
-	private class ReportCrashAgent : InternalAgent {
+	private sealed class ReportCrashAgent : InternalAgent {
 		public signal void crash_detected (uint pid);
 		public signal void crash_received (CrashInfo crash);
 
@@ -1289,7 +1215,7 @@ namespace Frida {
 		}
 	}
 
-	private class OSAnalyticsAgent : InternalAgent {
+	private sealed class OSAnalyticsAgent : InternalAgent {
 		public uint pid {
 			get;
 			construct;

src/darwin/frida-helper-backend.vala

@@ -686,7 +686,7 @@ namespace Frida {
 		protected extern void _close_inject_instance (void * instance);
 	}
 
-	public class DTraceAgent : Object {
+	public sealed class DTraceAgent : Object {
 		public signal void spawn_added (HostSpawnInfo info);
 		public signal void spawn_removed (HostSpawnInfo info);
 
@@ -845,7 +845,7 @@ namespace Frida {
 		}
 	}
 
-	private class PendingLaunch : Object {
+	private sealed class PendingLaunch : Object {
 		public signal void completed ();
 
 		public string identifier {
@@ -889,7 +889,7 @@ namespace Frida {
 		}
 	}
 
-	public class StdioPipes : Object {
+	public sealed class StdioPipes : Object {
 		public int input {
 			get;
 			construct;

src/darwin/frida-helper-null-backend.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class DarwinHelperBackend : Object, DarwinHelper {
+	public sealed class DarwinHelperBackend : Object, DarwinHelper {
 		public signal void idle ();
 		public signal void child_dead (uint pid);
 		public signal void spawn_instance_ready (uint pid);

src/darwin/frida-helper-process.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class DarwinHelperProcess : Object, DarwinHelper {
+	public sealed class DarwinHelperProcess : Object, DarwinHelper {
 		public uint pid {
 			get {
 				return (uint) process_pid;
@@ -473,7 +473,7 @@ namespace Frida {
 		}
 	}
 
-	private class ResourceStore {
+	private sealed class ResourceStore {
 		public HelperFile helper {
 			get;
 			private set;

src/darwin/frida-helper-service.vala

@@ -22,7 +22,7 @@ namespace Frida {
 	public extern void _start_run_loop ();
 	public extern void _stop_run_loop ();
 
-	public class DarwinHelperService : Object, DarwinRemoteHelper {
+	public sealed class DarwinHelperService : Object, DarwinRemoteHelper {
 		public string parent_address {
 			get;
 			construct;

src/darwin/fruitjector.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class Fruitjector : Object, Injector {
+	public sealed class Fruitjector : Object, Injector {
 		public signal void injected (uint id, uint pid, bool has_mapped_module, DarwinModuleDetails mapped_module);
 
 		public DarwinHelper helper {
@@ -117,7 +117,7 @@ namespace Frida {
 		}
 	}
 
-	public class AgentResource : Object {
+	public sealed class AgentResource : Object {
 		public string name {
 			get;
 			construct;

src/darwin/policy-softener.vala

@@ -6,7 +6,7 @@ namespace Frida {
 		public abstract void forget (uint pid);
 	}
 
-	public class NullPolicySoftener : Object, PolicySoftener {
+	public sealed class NullPolicySoftener : Object, PolicySoftener {
 		public void soften (uint pid) throws Error {
 		}
 
@@ -164,7 +164,7 @@ namespace Frida {
 		}
 	}
 
-	public class InternalIOSTVOSPolicySoftener : IOSTVOSPolicySoftener {
+	public sealed class InternalIOSTVOSPolicySoftener : IOSTVOSPolicySoftener {
 		private static bool enabled = false;
 
 		public static void enable () {
@@ -184,7 +184,7 @@ namespace Frida {
 		private extern static void _soften (uint pid) throws Error;
 	}
 
-	public class ElectraPolicySoftener : IOSTVOSPolicySoftener {
+	public sealed class ElectraPolicySoftener : IOSTVOSPolicySoftener {
 		private const string LIBJAILBREAK_PATH = "/usr/lib/libjailbreak.dylib";
 
 		private Module libjailbreak;
@@ -237,7 +237,7 @@ namespace Frida {
 		private extern static int _internal_jb_entitle_now (void * jbd_call, uint connection, uint pid);
 	}
 
-	public class Unc0verPolicySoftener : IOSTVOSPolicySoftener {
+	public sealed class Unc0verPolicySoftener : IOSTVOSPolicySoftener {
 		private const string SUBSTITUTED_PATH = "/usr/libexec/substituted";
 
 		private uint connection;

src/droidy/axml.vala

@@ -69,7 +69,7 @@ namespace Frida.AXML {
 		}
 	}
 
-	public class ElementTree : Object {
+	public sealed class ElementTree : Object {
 		public string name {
 			get;
 			set;
@@ -135,7 +135,7 @@ namespace Frida.AXML {
 		}
 	}
 
-	public class ResourceValue : Object {
+	public sealed class ResourceValue : Object {
 		private uint16 size;
 		private uint8 unused;
 		private ResourceType type;
@@ -173,7 +173,7 @@ namespace Frida.AXML {
 		}
 	}
 
-	public class Attribute : Object {
+	public sealed class Attribute : Object {
 		private uint32 namespace;
 		private uint32 name;
 		private uint32 unused;
@@ -238,7 +238,7 @@ namespace Frida.AXML {
 		}
 	}
 
-	private class ResourceMap {
+	private sealed class ResourceMap {
 		private Gee.ArrayList<uint32> resources = new Gee.ArrayList<uint32> ();
 
 		public ResourceMap.with_stream (DataInputStream input, uint32 size) throws IOError {
@@ -247,7 +247,7 @@ namespace Frida.AXML {
 		}
 	}
 
-	private class StringPool {
+	private sealed class StringPool {
 		private uint32 flags;
 		private Gee.ArrayList<string> strings = new Gee.ArrayList<string> ();
 

src/droidy/droidy-client.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaDroidy", gir_version = "1.0")]
 namespace Frida.Droidy {
-	public class DeviceTracker : Object {
+	public sealed class DeviceTracker : Object {
 		public signal void device_attached (DeviceDetails details);
 		public signal void device_detached (string serial);
 
@@ -149,7 +149,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class DeviceDetails : Object {
+	public sealed class DeviceDetails : Object {
 		public string serial {
 			get;
 			construct;
@@ -205,7 +205,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class ShellSession : Object {
+	public sealed class ShellSession : Object {
 		public signal void output (StdioPipe pipe, Bytes bytes);
 		public signal void closed ();
 
@@ -594,7 +594,7 @@ namespace Frida.Droidy {
 		STDERR
 	}
 
-	public class ShellCommandResult : Object {
+	public sealed class ShellCommandResult : Object {
 		public uint8 status {
 			get;
 			construct;
@@ -686,7 +686,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class FileMetadata : Object {
+	public sealed class FileMetadata : Object {
 		public uint32 mode {
 			get;
 			set;
@@ -700,7 +700,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class JDWPTracker : Object {
+	public sealed class JDWPTracker : Object {
 		public signal void debugger_attached (uint pid);
 		public signal void debugger_detached (uint pid);
 
@@ -768,7 +768,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class Client : Object {
+	public sealed class Client : Object {
 		public signal void closed ();
 		public signal void message (string payload);
 
@@ -1154,7 +1154,7 @@ namespace Frida.Droidy {
 		}
 	}
 
-	public class SyncSession : Object {
+	public sealed class SyncSession : Object {
 		public Client client {
 			get;
 			construct;

src/droidy/droidy-host-session.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class DroidyHostSessionBackend : Object, HostSessionBackend {
+	public sealed class DroidyHostSessionBackend : Object, HostSessionBackend {
 		private Droidy.DeviceTracker tracker;
 
 		private Gee.HashMap<string, DroidyHostSessionProvider> providers = new Gee.HashMap<string, DroidyHostSessionProvider> ();
@@ -86,7 +86,7 @@ namespace Frida {
 		}
 	}
 
-	public class DroidyHostSessionProvider : Object, HostSessionProvider, HostChannelProvider {
+	public sealed class DroidyHostSessionProvider : Object, HostSessionProvider, HostChannelProvider {
 		public string id {
 			get { return device_details.serial; }
 		}
@@ -158,6 +158,36 @@ namespace Frida {
 			return yield this.host_session.link_agent_session (id, sink, cancellable);
 		}
 
+		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_agent_session (id);
+		}
+
+		public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+				throws Error, IOError {
+			if (host_session != this.host_session)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+
+			return this.host_session.link_channel (id);
+		}
+
+		public void unlink_channel (HostSession host_session, ChannelId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_channel (id);
+		}
+
+		public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id, Cancellable? cancellable)
+				throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
+		public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+		}
+
 		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
 			agent_session_detached (id, reason, crash);
 		}
@@ -182,7 +212,7 @@ namespace Frida {
 		}
 	}
 
-	public class DroidyHostSession : Object, HostSession {
+	public sealed class DroidyHostSession : Object, HostSession {
 		public Droidy.DeviceDetails device_details {
 			get;
 			construct;
@@ -211,6 +241,8 @@ namespace Frida {
 		private Gee.HashMap<AgentSessionId?, AgentSessionEntry> agent_sessions =
 			new Gee.HashMap<AgentSessionId?, AgentSessionEntry> (AgentSessionId.hash, AgentSessionId.equal);
 
+		private ChannelRegistry channel_registry = new ChannelRegistry ();
+
 		private Cancellable io_cancellable = new Cancellable ();
 
 		private const double MIN_SERVER_CHECK_INTERVAL = 5.0;
@@ -223,6 +255,10 @@ namespace Frida {
 			);
 		}
 
+		construct {
+			channel_registry.channel_closed.connect (on_channel_closed);
+		}
+
 		public async void close (Cancellable? cancellable) throws IOError {
 			if (remote_server_request != null) {
 				var server = yield try_get_remote_server (cancellable);
@@ -832,6 +868,15 @@ namespace Frida {
 			return session;
 		}
 
+		public void unlink_agent_session (AgentSessionId id) {
+			AgentSessionEntry? entry = agent_sessions[id];
+			if (entry == null || entry.sink_registration_id == 0)
+				return;
+
+			entry.connection.unregister_object (entry.sink_registration_id);
+			entry.sink_registration_id = 0;
+		}
+
 		public async InjectorPayloadId inject_library_file (uint pid, string path, string entrypoint, string data,
 				Cancellable? cancellable) throws Error, IOError {
 			var server = yield get_remote_server (cancellable);
@@ -852,6 +897,31 @@ namespace Frida {
 			}
 		}
 
+		public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+			var stream = yield channel_provider.open_channel (address, cancellable);
+
+			var id = ChannelId.generate ();
+			channel_registry.register (id, stream);
+
+			return id;
+		}
+
+		public IOStream link_channel (ChannelId id) throws Error {
+			return channel_registry.link (id);
+		}
+
+		public void unlink_channel (ChannelId id) {
+			channel_registry.unlink (id);
+		}
+
+		private void on_channel_closed (ChannelId id) {
+			channel_closed (id);
+		}
+
+		public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
 		private void on_gadget_entry_detached (GadgetEntry entry, SessionDetachReason reason) {
 			AgentSessionId id = entry.local_session_id;
 			var no_crash = CrashInfo.empty ();
@@ -1217,7 +1287,7 @@ namespace Frida {
 			}
 		}
 
-		public class HelperClient : Object, AsyncInitable {
+		public sealed class HelperClient : Object, AsyncInitable {
 			public signal void closed ();
 
 			public string device_serial {

src/droidy/injector.vala

@@ -6,7 +6,7 @@ namespace Frida.Droidy.Injector {
 		return yield session.run (cancellable);
 	}
 
-	public class GadgetDetails : Object {
+	public sealed class GadgetDetails : Object {
 		public uint pid {
 			get;
 			construct;
@@ -31,7 +31,7 @@ namespace Frida.Droidy.Injector {
 		}
 	}
 
-	private class Session : Object {
+	private sealed class Session : Object {
 		public InputStream gadget {
 			get;
 			construct;

src/droidy/jdwp.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaJDWP", gir_version = "1.0")]
 namespace Frida.JDWP {
-	public class Client : GLib.Object, AsyncInitable {
+	public sealed class Client : GLib.Object, AsyncInitable {
 		public signal void closed ();
 		public signal void events_received (Events events);
 
@@ -593,7 +593,7 @@ namespace Frida.JDWP {
 		public abstract string to_string ();
 	}
 
-	public class Byte : Value {
+	public sealed class Byte : Value {
 		public uint8 val {
 			get;
 			construct;
@@ -608,7 +608,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Char : Value {
+	public sealed class Char : Value {
 		public string val {
 			get;
 			construct;
@@ -623,7 +623,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Double : Value {
+	public sealed class Double : Value {
 		public double val {
 			get;
 			construct;
@@ -638,7 +638,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Float : Value {
+	public sealed class Float : Value {
 		public float val {
 			get;
 			construct;
@@ -653,7 +653,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Int : Value {
+	public sealed class Int : Value {
 		public int32 val {
 			get;
 			construct;
@@ -668,7 +668,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Long : Value {
+	public sealed class Long : Value {
 		public int64 val {
 			get;
 			construct;
@@ -698,7 +698,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Short : Value {
+	public sealed class Short : Value {
 		public int16 val {
 			get;
 			construct;
@@ -713,7 +713,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Void : Value {
+	public sealed class Void : Value {
 		public Void () {
 			GLib.Object (tag: ValueTag.VOID);
 		}
@@ -723,7 +723,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Boolean : Value {
+	public sealed class Boolean : Value {
 		public bool val {
 			get;
 			construct;
@@ -738,43 +738,43 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Array : Object {
+	public sealed class Array : Object {
 		public Array (ObjectID val) {
 			GLib.Object (tag: ValueTag.ARRAY, val: val);
 		}
 	}
 
-	public class ClassObject : Object {
+	public sealed class ClassObject : Object {
 		public ClassObject (ObjectID val) {
 			GLib.Object (tag: ValueTag.CLASS_OBJECT, val: val);
 		}
 	}
 
-	public class ThreadGroup : Object {
+	public sealed class ThreadGroup : Object {
 		public ThreadGroup (ObjectID val) {
 			GLib.Object (tag: ValueTag.THREAD_GROUP, val: val);
 		}
 	}
 
-	public class ClassLoader : Object {
+	public sealed class ClassLoader : Object {
 		public ClassLoader (ObjectID val) {
 			GLib.Object (tag: ValueTag.CLASS_LOADER, val: val);
 		}
 	}
 
-	public class String : Object {
+	public sealed class String : Object {
 		public String (ObjectID val) {
 			GLib.Object (tag: ValueTag.STRING, val: val);
 		}
 	}
 
-	public class Thread : Object {
+	public sealed class Thread : Object {
 		public Thread (ObjectID val) {
 			GLib.Object (tag: ValueTag.THREAD, val: val);
 		}
 	}
 
-	public class ClassInfo : GLib.Object {
+	public sealed class ClassInfo : GLib.Object {
 		public TaggedReferenceTypeID ref_type {
 			get;
 			construct;
@@ -815,7 +815,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MethodInfo : GLib.Object {
+	public sealed class MethodInfo : GLib.Object {
 		public MethodID id {
 			get;
 			construct;
@@ -992,7 +992,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class Location : GLib.Object {
+	public sealed class Location : GLib.Object {
 		public TaggedReferenceTypeID declaring {
 			get;
 			construct;
@@ -1071,7 +1071,7 @@ namespace Frida.JDWP {
 		ALL          = 2,
 	}
 
-	public class Events : GLib.Object {
+	public sealed class Events : GLib.Object {
 		public SuspendPolicy suspend_policy {
 			get;
 			construct;
@@ -1119,7 +1119,7 @@ namespace Frida.JDWP {
 		public abstract string to_string ();
 	}
 
-	public class SingleStepEvent : Event {
+	public sealed class SingleStepEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1155,7 +1155,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class BreakpointEvent : Event {
+	public sealed class BreakpointEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1191,7 +1191,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class FramePopEvent : Event {
+	public sealed class FramePopEvent : Event {
 		public override string to_string () {
 			return "FramePopEvent()";
 		}
@@ -1201,7 +1201,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ExceptionEvent : Event {
+	public sealed class ExceptionEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1254,7 +1254,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class UserDefinedEvent : Event {
+	public sealed class UserDefinedEvent : Event {
 		public override string to_string () {
 			return "UserDefinedEvent()";
 		}
@@ -1264,7 +1264,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ThreadStartEvent : Event {
+	public sealed class ThreadStartEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1292,7 +1292,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ThreadDeathEvent : Event {
+	public sealed class ThreadDeathEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1320,7 +1320,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassPrepareEvent : Event {
+	public sealed class ClassPrepareEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1373,7 +1373,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassUnloadEvent : Event {
+	public sealed class ClassUnloadEvent : Event {
 		public string signature {
 			get;
 			construct;
@@ -1398,7 +1398,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassLoadEvent : Event {
+	public sealed class ClassLoadEvent : Event {
 		public override string to_string () {
 			return "ClassLoadEvent()";
 		}
@@ -1435,7 +1435,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class FieldAccessEvent : FieldEvent {
+	public sealed class FieldAccessEvent : FieldEvent {
 		public FieldAccessEvent (EventRequestID request, ThreadID thread, Location location, TaggedReferenceTypeID ref_type,
 				FieldID field, TaggedObjectID object) {
 			GLib.Object (
@@ -1471,7 +1471,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class FieldModificationEvent : FieldEvent {
+	public sealed class FieldModificationEvent : FieldEvent {
 		public Value value_to_be {
 			get;
 			construct;
@@ -1516,7 +1516,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ExceptionCatchEvent : Event {
+	public sealed class ExceptionCatchEvent : Event {
 		public override string to_string () {
 			return "ExceptionCatchEvent()";
 		}
@@ -1538,7 +1538,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MethodEntryEvent : MethodEvent {
+	public sealed class MethodEntryEvent : MethodEvent {
 		public MethodEntryEvent (EventRequestID request, ThreadID thread, Location location) {
 			GLib.Object (
 				kind: EventKind.METHOD_ENTRY,
@@ -1564,7 +1564,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MethodExitEvent : MethodEvent {
+	public sealed class MethodExitEvent : MethodEvent {
 		public MethodExitEvent (EventRequestID request, ThreadID thread, Location location) {
 			GLib.Object (
 				kind: EventKind.METHOD_EXIT,
@@ -1590,7 +1590,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MethodExitWithReturnValueEvent : MethodEvent {
+	public sealed class MethodExitWithReturnValueEvent : MethodEvent {
 		public Value retval {
 			get;
 			construct;
@@ -1641,7 +1641,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MonitorContendedEnterEvent : MonitorEvent {
+	public sealed class MonitorContendedEnterEvent : MonitorEvent {
 		public MonitorContendedEnterEvent (EventRequestID request, ThreadID thread, TaggedObjectID object, Location location) {
 			GLib.Object (
 				kind: EventKind.MONITOR_CONTENDED_ENTER,
@@ -1670,7 +1670,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MonitorContendedEnteredEvent : MonitorEvent {
+	public sealed class MonitorContendedEnteredEvent : MonitorEvent {
 		public MonitorContendedEnteredEvent (EventRequestID request, ThreadID thread, TaggedObjectID object, Location location) {
 			GLib.Object (
 				kind: EventKind.MONITOR_CONTENDED_ENTERED,
@@ -1699,7 +1699,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MonitorWaitEvent : MonitorEvent {
+	public sealed class MonitorWaitEvent : MonitorEvent {
 		public int64 timeout {
 			get;
 			construct;
@@ -1736,7 +1736,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class MonitorWaitedEvent : MonitorEvent {
+	public sealed class MonitorWaitedEvent : MonitorEvent {
 		public bool timed_out {
 			get;
 			construct;
@@ -1774,7 +1774,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class VMStartEvent : Event {
+	public sealed class VMStartEvent : Event {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1799,7 +1799,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class VMDeathEvent : Event {
+	public sealed class VMDeathEvent : Event {
 		public VMDeathEvent (EventRequestID request) {
 			GLib.Object (kind: EventKind.VM_DEATH, request: request);
 		}
@@ -1814,7 +1814,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class VMDisconnectedEvent : Event {
+	public sealed class VMDisconnectedEvent : Event {
 		public override string to_string () {
 			return "VMDisconnectedEvent()";
 		}
@@ -1828,7 +1828,7 @@ namespace Frida.JDWP {
 		internal abstract void serialize (PacketBuilder builder);
 	}
 
-	public class CountModifier : EventModifier {
+	public sealed class CountModifier : EventModifier {
 		public int32 count {
 			get;
 			construct;
@@ -1845,7 +1845,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ThreadOnlyModifier : EventModifier {
+	public sealed class ThreadOnlyModifier : EventModifier {
 		public ThreadID thread {
 			get;
 			construct;
@@ -1862,7 +1862,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassOnlyModifier : EventModifier {
+	public sealed class ClassOnlyModifier : EventModifier {
 		public ReferenceTypeID clazz {
 			get;
 			construct;
@@ -1879,7 +1879,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassMatchModifier : EventModifier {
+	public sealed class ClassMatchModifier : EventModifier {
 		public string class_pattern {
 			get;
 			construct;
@@ -1896,7 +1896,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ClassExcludeModifier : EventModifier {
+	public sealed class ClassExcludeModifier : EventModifier {
 		public string class_pattern {
 			get;
 			construct;
@@ -1913,7 +1913,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class LocationOnlyModifier : EventModifier {
+	public sealed class LocationOnlyModifier : EventModifier {
 		public Location location {
 			get;
 			construct;
@@ -1929,7 +1929,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class ExceptionOnlyModifier : EventModifier {
+	public sealed class ExceptionOnlyModifier : EventModifier {
 		public ReferenceTypeID exception_or_null {
 			get;
 			construct;
@@ -1962,7 +1962,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class FieldOnlyModifier : EventModifier {
+	public sealed class FieldOnlyModifier : EventModifier {
 		public ReferenceTypeID declaring {
 			get;
 			construct;
@@ -1988,7 +1988,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class StepModifier : EventModifier {
+	public sealed class StepModifier : EventModifier {
 		public ThreadID thread {
 			get;
 			construct;
@@ -2032,7 +2032,7 @@ namespace Frida.JDWP {
 		OUT  = 2,
 	}
 
-	public class InstanceOnlyModifier : EventModifier {
+	public sealed class InstanceOnlyModifier : EventModifier {
 		public ObjectID instance {
 			get;
 			construct;
@@ -2049,7 +2049,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	public class SourceNameMatchModifier : EventModifier {
+	public sealed class SourceNameMatchModifier : EventModifier {
 		public string source_name_pattern {
 			get;
 			construct;
@@ -2149,7 +2149,7 @@ namespace Frida.JDWP {
 		REPLY = (1 << 7),
 	}
 
-	private class CommandBuilder : PacketBuilder {
+	private sealed class CommandBuilder : PacketBuilder {
 		public CommandBuilder (uint32 id, CommandSet command_set, uint8 command, IDSizes id_sizes) {
 			base (id, 0, id_sizes);
 
@@ -2354,7 +2354,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	private class PacketReader {
+	private sealed class PacketReader {
 		public size_t available_bytes {
 			get {
 				return end - cursor;
@@ -2574,7 +2574,7 @@ namespace Frida.JDWP {
 		}
 	}
 
-	private class IDSizes {
+	private sealed class IDSizes {
 		private bool valid;
 		private int field_id_size = -1;
 		private int method_id_size = -1;

src/file-monitor.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class FileMonitor : Object {
+	public sealed class FileMonitor : Object {
 		public signal void change (string file_path, string? other_file_path, FileMonitorEvent event);
 
 		public string path {

src/freebsd/binjector.vala

@@ -408,7 +408,7 @@ namespace Frida {
 		protected extern InputStream _get_fifo_for_inject_instance (void * instance);
 		protected extern void _free_inject_instance (void * instance, UnloadPolicy unload_policy);
 
-		public class ResourceStore {
+		public sealed class ResourceStore {
 			public TemporaryDirectory tempdir {
 				get;
 				private set;
@@ -439,7 +439,7 @@ namespace Frida {
 		}
 	}
 
-	public class AgentDescriptor : Object {
+	public sealed class AgentDescriptor : Object {
 		public string name {
 			get;
 			construct;
@@ -553,7 +553,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteModule {
+	private sealed class RemoteModule {
 		private Gum.Address base_address;
 		private Gum.ElfModule module;
 
@@ -587,7 +587,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteThreadSession : Object {
+	private sealed class RemoteThreadSession : Object {
 		public signal void ended (UnloadPolicy unload_policy);
 
 		public uint id {

src/freebsd/freebsd-host-session.vala

@@ -1,82 +1,17 @@
 namespace Frida {
-	public class FreebsdHostSessionBackend : Object, HostSessionBackend {
-		private FreebsdHostSessionProvider local_provider;
-
-		public async void start (Cancellable? cancellable) throws IOError {
-			assert (local_provider == null);
-			local_provider = new FreebsdHostSessionProvider ();
-			provider_available (local_provider);
-		}
-
-		public async void stop (Cancellable? cancellable) throws IOError {
-			assert (local_provider != null);
-			provider_unavailable (local_provider);
-			yield local_provider.close (cancellable);
-			local_provider = null;
+	public sealed class FreebsdHostSessionBackend : LocalHostSessionBackend {
+		protected override LocalHostSessionProvider make_provider () {
+			return new FreebsdHostSessionProvider ();
 		}
 	}
 
-	public class FreebsdHostSessionProvider : Object, HostSessionProvider {
-		public string id {
-			get { return "local"; }
-		}
-
-		public string name {
-			get { return "Local System"; }
-		}
-
-		public Variant? icon {
-			get { return null; }
-		}
-
-		public HostSessionProviderKind kind {
-			get { return HostSessionProviderKind.LOCAL; }
-		}
-
-		private FreebsdHostSession host_session;
-
-		public async void close (Cancellable? cancellable) throws IOError {
-			if (host_session == null)
-				return;
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async HostSession create (HostSessionOptions? options, Cancellable? cancellable) throws Error, IOError {
-			if (host_session != null)
-				throw new Error.INVALID_OPERATION ("Already created");
-
-			host_session = new FreebsdHostSession ();
-			host_session.agent_session_detached.connect (on_agent_session_detached);
-
-			return host_session;
-		}
-
-		public async void destroy (HostSession session, Cancellable? cancellable) throws Error, IOError {
-			if (session != host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
-				Cancellable? cancellable) throws Error, IOError {
-			if (host_session != this.host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			return yield this.host_session.link_agent_session (id, sink, cancellable);
-		}
-
-		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
-			agent_session_detached (id, reason, crash);
+	public sealed class FreebsdHostSessionProvider : LocalHostSessionProvider {
+		protected override LocalHostSession make_host_session (HostSessionOptions? options) throws Error {
+			return new FreebsdHostSession ();
 		}
 	}
 
-	public class FreebsdHostSession : BaseDBusHostSession {
+	public sealed class FreebsdHostSession : LocalHostSession {
 		private AgentContainer system_session_container;
 
 		private AgentDescriptor agent_desc;

src/frida.vala

@@ -24,7 +24,7 @@ namespace Frida {
 		}
 	}
 
-	public class DeviceManager : Object {
+	public sealed class DeviceManager : Object {
 		public signal void added (Device device);
 		public signal void removed (Device device);
 		public signal void changed ();
@@ -468,7 +468,7 @@ namespace Frida {
 		}
 	}
 
-	public class DeviceList : Object {
+	public sealed class DeviceList : Object {
 		private Gee.List<Device> items;
 
 		internal DeviceList (Gee.List<Device> items) {
@@ -484,7 +484,7 @@ namespace Frida {
 		}
 	}
 
-	public class Device : Object {
+	public sealed class Device : Object {
 		public signal void spawn_added (Spawn spawn);
 		public signal void spawn_removed (Spawn spawn);
 		public signal void child_added (Child child);
@@ -551,7 +551,6 @@ namespace Frida {
 		private Gee.HashSet<Promise<Session>> pending_attach_requests = new Gee.HashSet<Promise<Session>> ();
 		private Gee.HashMap<AgentSessionId?, Promise<bool>> pending_detach_requests =
 			new Gee.HashMap<AgentSessionId?, Promise<bool>> (AgentSessionId.hash, AgentSessionId.equal);
-		private Gee.Set<Service> services = new Gee.HashSet<Service> ();
 		private Bus _bus;
 
 		public delegate bool ProcessPredicate (Process process);
@@ -1238,11 +1237,16 @@ namespace Frida {
 		public async IOStream open_channel (string address, Cancellable? cancellable = null) throws Error, IOError {
 			check_open ();
 
-			var channel_provider = provider as HostChannelProvider;
-			if (channel_provider == null)
-				throw new Error.NOT_SUPPORTED ("Channels are not supported by this device");
+			var host_session = yield get_host_session (cancellable);
 
-			return yield channel_provider.open_channel (address, cancellable);
+			ChannelId id;
+			try {
+				id = yield host_session.open_channel (address, cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
+
+			return yield provider.link_channel (host_session, id, cancellable);
 		}
 
 		public IOStream open_channel_sync (string address, Cancellable? cancellable = null) throws Error, IOError {
@@ -1262,15 +1266,18 @@ namespace Frida {
 		public async Service open_service (string address, Cancellable? cancellable = null) throws Error, IOError {
 			check_open ();
 
-			var service_provider = provider as HostServiceProvider;
-			if (service_provider == null)
-				throw new Error.NOT_SUPPORTED ("Services are not supported by this device");
+			var host_session = yield get_host_session (cancellable);
 
-			var service = yield service_provider.open_service (address, cancellable);
-			service.close.connect (on_service_closed);
-			services.add (service);
+			ServiceSessionId id;
+			try {
+				id = yield host_session.open_service (address, cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
 
-			return service;
+			var service_session = yield provider.link_service_session (host_session, id, cancellable);
+
+			return new Service (service_session);
 		}
 
 		public Service open_service_sync (string address, Cancellable? cancellable = null) throws Error, IOError {
@@ -1287,10 +1294,6 @@ namespace Frida {
 			}
 		}
 
-		private void on_service_closed (Service service) {
-			services.remove (service);
-		}
-
 		public async void unpair (Cancellable? cancellable = null) throws Error, IOError {
 			check_open ();
 
@@ -1389,10 +1392,6 @@ namespace Frida {
 			close_request = new Promise<bool> ();
 
 			try {
-				foreach (var service in services.to_array ())
-					yield service.cancel (cancellable);
-				services.clear ();
-
 				while (!pending_detach_requests.is_empty) {
 					var iterator = pending_detach_requests.entries.iterator ();
 					iterator.next ();
@@ -1546,7 +1545,7 @@ namespace Frida {
 		}
 	}
 
-	public class RemoteDeviceOptions : Object {
+	public sealed class RemoteDeviceOptions : Object {
 		public TlsCertificate? certificate {
 			get;
 			set;
@@ -1569,7 +1568,7 @@ namespace Frida {
 		}
 	}
 
-	public class ApplicationList : Object {
+	public sealed class ApplicationList : Object {
 		private Gee.List<Application> items;
 
 		internal ApplicationList (Gee.List<Application> items) {
@@ -1585,7 +1584,7 @@ namespace Frida {
 		}
 	}
 
-	public class Application : Object {
+	public sealed class Application : Object {
 		public string identifier {
 			get;
 			construct;
@@ -1611,7 +1610,7 @@ namespace Frida {
 		}
 	}
 
-	public class ProcessList : Object {
+	public sealed class ProcessList : Object {
 		private Gee.List<Process> items;
 
 		internal ProcessList (Gee.List<Process> items) {
@@ -1627,7 +1626,7 @@ namespace Frida {
 		}
 	}
 
-	public class Process : Object {
+	public sealed class Process : Object {
 		public uint pid {
 			get;
 			construct;
@@ -1648,7 +1647,7 @@ namespace Frida {
 		}
 	}
 
-	public class ProcessMatchOptions : Object {
+	public sealed class ProcessMatchOptions : Object {
 		public int timeout {
 			get;
 			set;
@@ -1662,7 +1661,7 @@ namespace Frida {
 		}
 	}
 
-	public class SpawnOptions : Object {
+	public sealed class SpawnOptions : Object {
 		public string[]? argv {
 			get;
 			set;
@@ -1696,7 +1695,7 @@ namespace Frida {
 		}
 	}
 
-	public class SpawnList : Object {
+	public sealed class SpawnList : Object {
 		private Gee.List<Spawn> items;
 
 		internal SpawnList (Gee.List<Spawn> items) {
@@ -1712,7 +1711,7 @@ namespace Frida {
 		}
 	}
 
-	public class Spawn : Object {
+	public sealed class Spawn : Object {
 		public uint pid {
 			get;
 			construct;
@@ -1736,7 +1735,7 @@ namespace Frida {
 		}
 	}
 
-	public class ChildList : Object {
+	public sealed class ChildList : Object {
 		private Gee.List<Child> items;
 
 		internal ChildList (Gee.List<Child> items) {
@@ -1752,7 +1751,7 @@ namespace Frida {
 		}
 	}
 
-	public class Child : Object {
+	public sealed class Child : Object {
 		public uint pid {
 			get;
 			construct;
@@ -1816,7 +1815,7 @@ namespace Frida {
 		}
 	}
 
-	public class Crash : Object {
+	public sealed class Crash : Object {
 		public uint pid {
 			get;
 			construct;
@@ -1865,7 +1864,7 @@ namespace Frida {
 		}
 	}
 
-	public class Bus : Object {
+	public sealed class Bus : Object {
 		public signal void detached ();
 		public signal void message (string json, Bytes? data);
 
@@ -2000,13 +1999,71 @@ namespace Frida {
 		}
 	}
 
-	public interface Service : Object {
+	public sealed class Service : Object {
 		public signal void close ();
 		public signal void message (Variant message);
 
-		public abstract bool is_closed ();
+		private ServiceSession? session;
+		private bool disposed = false;
 
-		public abstract async void activate (Cancellable? cancellable = null) throws Error, IOError;
+		internal Service (ServiceSession session) {
+			this.session = session;
+
+			session.close.connect (on_close);
+			session.message.connect (on_message);
+		}
+
+		public override void dispose () {
+			if (!disposed) {
+				disposed = true;
+
+				MainContext context = get_main_context ();
+				if (context.is_owner ()) {
+					abandon ();
+				} else {
+					var source = new IdleSource ();
+					source.set_callback (() => {
+						abandon ();
+						return false;
+					});
+					source.attach (context);
+				}
+			}
+
+			base.dispose ();
+		}
+
+		~Service () {
+			forget_session ();
+		}
+
+		private void abandon () {
+			var s = session;
+			if (s != null) {
+				forget_session ();
+				s.cancel.begin (null);
+			}
+		}
+
+		private void forget_session () {
+			session.close.disconnect (on_close);
+			session.message.disconnect (on_message);
+			session = null;
+		}
+
+		public bool is_closed () {
+			return session == null;
+		}
+
+		public async void activate (Cancellable? cancellable = null) throws Error, IOError {
+			check_open ();
+
+			try {
+				yield session.activate (cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
+		}
 
 		public void activate_sync (Cancellable? cancellable = null) throws Error, IOError {
 			create<ActivateTask> ().execute (cancellable);
@@ -2018,7 +2075,17 @@ namespace Frida {
 			}
 		}
 
-		public abstract async void cancel (Cancellable? cancellable = null) throws IOError;
+		public async void cancel (Cancellable? cancellable = null) throws IOError {
+			if (session == null)
+				return;
+
+			try {
+				yield session.cancel (cancellable);
+			} catch (GLib.Error e) {
+				if (e is IOError.CANCELLED)
+					cancellable.set_error_if_cancelled ();
+			}
+		}
 
 		public void cancel_sync (Cancellable? cancellable = null) throws IOError {
 			try {
@@ -2034,7 +2101,15 @@ namespace Frida {
 			}
 		}
 
-		public abstract async Variant request (Variant parameters, Cancellable? cancellable = null) throws Error, IOError;
+		public async Variant request (Variant parameters, Cancellable? cancellable = null) throws Error, IOError {
+			check_open ();
+
+			try {
+				return yield session.request (parameters, cancellable);
+			} catch (GLib.Error e) {
+				throw_dbus_error (e);
+			}
+		}
 
 		public Variant request_sync (Variant parameters, Cancellable? cancellable = null) throws Error, IOError {
 			var task = create<RequestTask> () as RequestTask;
@@ -2050,6 +2125,20 @@ namespace Frida {
 			}
 		}
 
+		private void check_open () throws Error {
+			if (session == null)
+				throw new Error.INVALID_OPERATION ("Session is gone");
+		}
+
+		private void on_close () {
+			forget_session ();
+			close ();
+		}
+
+		private void on_message (Variant v) {
+			message (v);
+		}
+
 		private T create<T> () {
 			return Object.new (typeof (T), parent: this);
 		}
@@ -2062,7 +2151,7 @@ namespace Frida {
 		}
 	}
 
-	public class Session : Object, AgentMessageSink {
+	public sealed class Session : Object, AgentMessageSink {
 		public signal void detached (SessionDetachReason reason, Crash? crash);
 
 		public uint pid {
@@ -3030,7 +3119,7 @@ namespace Frida {
 		}
 	}
 
-	public class Script : Object {
+	public sealed class Script : Object {
 		public signal void destroyed ();
 		public signal void message (string json, Bytes? data);
 
@@ -3267,7 +3356,7 @@ namespace Frida {
 		}
 	}
 
-	public class PortalMembership : Object {
+	public sealed class PortalMembership : Object {
 		private uint id;
 		private Session session;
 

src/fruity/device-monitor-linux.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class LinuxFruitFinder : Object, FruitFinder {
+	public sealed class LinuxFruitFinder : Object, FruitFinder {
 		public string? udid_from_iface (string ifname) throws Error {
 			var net = "/sys/class/net";
 
@@ -34,7 +34,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class LinuxPairingBrowser : Object, PairingBrowser {
+	public sealed class LinuxPairingBrowser : Object, PairingBrowser {
 		private Resolved.Manager? resolved;
 		private Source? timer;
 

src/fruity/device-monitor-macos.vala

@@ -411,7 +411,7 @@ namespace Frida.Fruity {
 			return new PcbList (pcbs);
 		}
 
-		public class PcbList {
+		public sealed class PcbList {
 			private uint8[] pcbs;
 
 			internal PcbList (owned uint8[] pcbs) {
@@ -422,7 +422,7 @@ namespace Frida.Fruity {
 				return new Iterator (this);
 			}
 
-			public class Iterator {
+			public sealed class Iterator {
 				private PcbList list;
 				private InetItem * cursor;
 
@@ -461,7 +461,7 @@ namespace Frida.Fruity {
 				}
 			}
 
-			public class Item {
+			public sealed class Item {
 				public SocketFamily family {
 					get {
 						return ((pcb.version_flag & Darwin.XNU.InetVersionFlags.IPV6) != 0)

src/fruity/device-monitor-windows.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class WindowsPairingBrowser : Object, PairingBrowser {
+	public sealed class WindowsPairingBrowser : Object, PairingBrowser {
 		private Gee.Map<string, Monitor> monitors = new Gee.HashMap<string, Monitor> ();
 
 		private MainContext main_context = MainContext.ref_thread_default ();

src/fruity/device-monitor.vala

@@ -1997,7 +1997,7 @@ namespace Frida.Fruity {
 		public abstract string? udid_from_iface (string ifname) throws Error;
 	}
 
-	public class NullFruitFinder : Object, FruitFinder {
+	public sealed class NullFruitFinder : Object, FruitFinder {
 		public string? udid_from_iface (string ifname) throws Error {
 			return null;
 		}
@@ -2022,7 +2022,7 @@ namespace Frida.Fruity {
 		public abstract async void stop (Cancellable? cancellable) throws IOError;
 	}
 
-	public class NullPairingBrowser : Object, PairingBrowser {
+	public sealed class NullPairingBrowser : Object, PairingBrowser {
 		public async void start (Cancellable? cancellable) throws IOError {
 		}
 

src/fruity/dns.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class DnsPacketReader {
+	public sealed class DnsPacketReader {
 		private BufferReader reader;
 
 		public DnsPacketReader (Bytes packet) {

src/fruity/dtx.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class DeviceInfoService : Object, AsyncInitable {
+	public sealed class DeviceInfoService : Object, AsyncInitable {
 		public HostChannelProvider channel_provider {
 			get;
 			construct;
@@ -75,7 +75,7 @@ namespace Frida.Fruity {
 			return name;
 		}
 
-		public class ProcessInfo : Object {
+		public sealed class ProcessInfo : Object {
 			public uint pid {
 				get;
 				set;
@@ -108,7 +108,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class ApplicationListingService : Object, AsyncInitable {
+	public sealed class ApplicationListingService : Object, AsyncInitable {
 		public HostChannelProvider channel_provider {
 			get;
 			construct;
@@ -211,7 +211,7 @@ namespace Frida.Fruity {
 			return result;
 		}
 
-		public class ApplicationInfo : Object {
+		public sealed class ApplicationInfo : Object {
 			public ApplicationType app_type {
 				get;
 				set;
@@ -306,7 +306,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class ProcessControlService : Object, AsyncInitable {
+	public sealed class ProcessControlService : Object, AsyncInitable {
 		public HostChannelProvider channel_provider {
 			get;
 			construct;
@@ -346,7 +346,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class DTXConnection : Object, DTXTransport {
+	public sealed class DTXConnection : Object, DTXTransport {
 		public IOStream stream {
 			get;
 			construct;
@@ -847,7 +847,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	private class DTXControlChannel : DTXChannel {
+	private sealed class DTXControlChannel : DTXChannel {
 		public DTXControlChannel (DTXTransport transport) {
 			Object (code: 0, transport: transport);
 		}
@@ -1161,7 +1161,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class DTXArgumentListBuilder {
+	public sealed class DTXArgumentListBuilder {
 		private PrimitiveBuilder blob = new PrimitiveBuilder ();
 
 		public DTXArgumentListBuilder () {
@@ -1227,7 +1227,7 @@ namespace Frida.Fruity {
 
 	private const size_t PRIMITIVE_DICTIONARY_HEADER_SIZE = 16;
 
-	private class PrimitiveReader {
+	private sealed class PrimitiveReader {
 		public size_t available_bytes {
 			get {
 				return end - cursor;
@@ -1317,7 +1317,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	private class PrimitiveBuilder {
+	private sealed class PrimitiveBuilder {
 		public size_t offset {
 			get {
 				return cursor;

src/fruity/fruity-host-session.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class FruityHostSessionBackend : Object, HostSessionBackend {
+	public sealed class FruityHostSessionBackend : Object, HostSessionBackend {
 		private Fruity.DeviceMonitor device_monitor = new Fruity.DeviceMonitor ();
 		private Gee.Map<Fruity.Device, FruityHostSessionProvider> providers =
 			new Gee.HashMap<Fruity.Device, FruityHostSessionProvider> ();
@@ -42,7 +42,7 @@ namespace Frida {
 		}
 	}
 
-	public class FruityHostSessionProvider : Object, HostSessionProvider, HostChannelProvider, HostServiceProvider, Pairable {
+	public sealed class FruityHostSessionProvider : Object, HostSessionProvider, HostChannelProvider, Pairable {
 		public Fruity.Device device {
 			get;
 			construct;
@@ -108,6 +108,43 @@ namespace Frida {
 			return yield this.host_session.link_agent_session (id, sink, cancellable);
 		}
 
+		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_agent_session (id);
+		}
+
+		public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+				throws Error, IOError {
+			if (host_session != this.host_session)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+
+			return this.host_session.link_channel (id);
+		}
+
+		public void unlink_channel (HostSession host_session, ChannelId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_channel (id);
+		}
+
+		public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id, Cancellable? cancellable)
+				throws Error, IOError {
+			if (host_session != this.host_session)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+
+			return this.host_session.link_service_session (id);
+		}
+
+		public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_service_session (id);
+		}
+
 		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
 			agent_session_detached (id, reason, crash);
 		}
@@ -116,37 +153,6 @@ namespace Frida {
 			return yield device.open_channel (address, cancellable);
 		}
 
-		public async Service open_service (string address, Cancellable? cancellable) throws Error, IOError {
-			string[] tokens = address.split (":", 2);
-			unowned string protocol = tokens[0];
-			unowned string service_name = tokens[1];
-
-			if (protocol == "plist") {
-				var stream = yield device.open_lockdown_service (service_name, cancellable);
-
-				return new PlistService (stream);
-			}
-
-			if (protocol == "dtx") {
-				var connection = yield Fruity.DTXConnection.obtain (device, cancellable);
-
-				return new DTXService (service_name, connection);
-			}
-
-			if (protocol == "xpc") {
-				var tunnel = yield device.find_tunnel (cancellable);
-				if (tunnel == null)
-					throw new Error.NOT_SUPPORTED ("RemoteXPC not supported by device");
-
-				var service_info = tunnel.discovery.get_service (service_name);
-				var stream = yield tunnel.open_tcp_connection (service_info.port, cancellable);
-
-				return new XpcService (new Fruity.XpcConnection (stream));
-			}
-
-			throw new Error.NOT_SUPPORTED ("Unsupported service address");
-		}
-
 		private async void unpair (Cancellable? cancellable) throws Error, IOError {
 			try {
 				var client = yield device.get_lockdown_client (cancellable);
@@ -159,7 +165,7 @@ namespace Frida {
 		}
 	}
 
-	public class FruityHostSession : Object, HostSession {
+	public sealed class FruityHostSession : Object, HostSession {
 		public Fruity.Device device {
 			get;
 			construct;
@@ -179,6 +185,10 @@ namespace Frida {
 		private Gee.HashMap<AgentSessionId?, AgentSessionEntry> agent_sessions =
 			new Gee.HashMap<AgentSessionId?, AgentSessionEntry> (AgentSessionId.hash, AgentSessionId.equal);
 
+		private ChannelRegistry channel_registry = new ChannelRegistry ();
+
+		private ServiceSessionRegistry service_session_registry = new ServiceSessionRegistry ();
+
 		private Cancellable io_cancellable = new Cancellable ();
 
 		private const double MIN_SERVER_CHECK_INTERVAL = 5.0;
@@ -196,6 +206,11 @@ namespace Frida {
 			Object (device: device);
 		}
 
+		construct {
+			channel_registry.channel_closed.connect (on_channel_closed);
+			service_session_registry.session_closed.connect (on_service_session_closed);
+		}
+
 		public async void close (Cancellable? cancellable) throws IOError {
 			if (remote_server_request != null) {
 				try {
@@ -999,6 +1014,15 @@ namespace Frida {
 			return session;
 		}
 
+		public void unlink_agent_session (AgentSessionId id) {
+			AgentSessionEntry? entry = agent_sessions[id];
+			if (entry == null || entry.sink_registration_id == 0)
+				return;
+
+			entry.connection.unregister_object (entry.sink_registration_id);
+			entry.sink_registration_id = 0;
+		}
+
 		public async InjectorPayloadId inject_library_file (uint pid, string path, string entrypoint, string data,
 				Cancellable? cancellable) throws Error, IOError {
 			var server = yield get_remote_server (cancellable);
@@ -1019,6 +1043,79 @@ namespace Frida {
 			}
 		}
 
+		public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+			var stream = yield device.open_channel (address, cancellable);
+
+			var id = ChannelId.generate ();
+			channel_registry.register (id, stream);
+
+			return id;
+		}
+
+		public IOStream link_channel (ChannelId id) throws Error {
+			return channel_registry.link (id);
+		}
+
+		public void unlink_channel (ChannelId id) {
+			channel_registry.unlink (id);
+		}
+
+		private void on_channel_closed (ChannelId id) {
+			channel_closed (id);
+		}
+
+		private void on_service_session_closed (ServiceSessionId id) {
+			service_session_closed (id);
+		}
+
+		public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			var session = yield do_open_service (address, cancellable);
+
+			var id = ServiceSessionId.generate ();
+			service_session_registry.register (id, session);
+
+			return id;
+		}
+
+		private async ServiceSession do_open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			string[] tokens = address.split (":", 2);
+			unowned string protocol = tokens[0];
+			unowned string service_name = tokens[1];
+
+			if (protocol == "plist") {
+				var stream = yield device.open_lockdown_service (service_name, cancellable);
+
+				return new PlistServiceSession (stream);
+			}
+
+			if (protocol == "dtx") {
+				var connection = yield Fruity.DTXConnection.obtain (device, cancellable);
+
+				return new DTXServiceSession (service_name, connection);
+			}
+
+			if (protocol == "xpc") {
+				var tunnel = yield device.find_tunnel (cancellable);
+				if (tunnel == null)
+					throw new Error.NOT_SUPPORTED ("RemoteXPC not supported by device");
+
+				var service_info = tunnel.discovery.get_service (service_name);
+				var stream = yield tunnel.open_tcp_connection (service_info.port, cancellable);
+
+				return new XpcServiceSession (new Fruity.XpcConnection (stream));
+			}
+
+			throw new Error.NOT_SUPPORTED ("Unsupported service address");
+		}
+
+		public ServiceSession link_service_session (ServiceSessionId id) throws Error {
+			return service_session_registry.link (id);
+		}
+
+		public void unlink_service_session (ServiceSessionId id) {
+			service_session_registry.unlink (id);
+		}
+
 		private void add_lldb_session (LLDBSession session) {
 			lldb_sessions[session.process.pid] = session;
 
@@ -1554,22 +1651,16 @@ namespace Frida {
 		}
 	}
 
-	private sealed class PlistService : Object, Service {
+	private sealed class PlistServiceSession : Object, ServiceSession {
 		public IOStream stream {
 			get;
 			construct;
 		}
 
-		private State state = INACTIVE;
 		private Fruity.PlistServiceClient client;
 		private bool client_closed = false;
 
-		private enum State {
-			INACTIVE,
-			ACTIVE,
-		}
-
-		public PlistService (IOStream stream) {
+		public PlistServiceSession (IOStream stream) {
 			Object (stream: stream);
 		}
 
@@ -1578,8 +1669,8 @@ namespace Frida {
 			client.closed.connect (on_client_closed);
 		}
 
-		public bool is_closed () {
-			return client_closed;
+		~PlistServiceSession () {
+			client.closed.disconnect (on_client_closed);
 		}
 
 		public async void activate (Cancellable? cancellable) throws Error, IOError {
@@ -1587,14 +1678,8 @@ namespace Frida {
 		}
 
 		private void ensure_active () throws Error {
-			if (state == INACTIVE) {
-				state = ACTIVE;
-
-				if (client_closed) {
-					close ();
-					throw new Error.INVALID_OPERATION ("Service is closed");
-				}
-			}
+			if (client_closed)
+				throw new Error.INVALID_OPERATION ("Service is closed");
 		}
 
 		public async void cancel (Cancellable? cancellable) throws IOError {
@@ -1603,6 +1688,8 @@ namespace Frida {
 			client_closed = true;
 
 			yield client.close (cancellable);
+
+			close ();
 		}
 
 		public async Variant request (Variant parameters, Cancellable? cancellable = null) throws Error, IOError {
@@ -1757,7 +1844,7 @@ namespace Frida {
 		}
 	}
 
-	private sealed class DTXService : Object, Service {
+	private sealed class DTXServiceSession : Object, ServiceSession {
 		public string identifier {
 			get;
 			construct;
@@ -1777,7 +1864,7 @@ namespace Frida {
 			ACTIVE,
 		}
 
-		public DTXService (string identifier, Fruity.DTXConnection connection) {
+		public DTXServiceSession (string identifier, Fruity.DTXConnection connection) {
 			Object (identifier: identifier, connection: connection);
 		}
 
@@ -1785,8 +1872,8 @@ namespace Frida {
 			connection.notify["state"].connect (on_connection_state_changed);
 		}
 
-		public bool is_closed () {
-			return connection_closed;
+		~DTXServiceSession () {
+			connection.notify["state"].disconnect (on_connection_state_changed);
 		}
 
 		public async void activate (Cancellable? cancellable) throws Error, IOError {
@@ -1794,14 +1881,12 @@ namespace Frida {
 		}
 
 		private void ensure_active () throws Error {
+			if (connection_closed)
+				throw new Error.INVALID_OPERATION ("Service is closed");
+
 			if (state == INACTIVE) {
 				state = ACTIVE;
 
-				if (connection_closed) {
-					close ();
-					throw new Error.INVALID_OPERATION ("Service is closed");
-				}
-
 				channel = connection.make_channel (identifier);
 				channel.invocation.connect (on_channel_invocation);
 				channel.notification.connect (on_channel_notification);
@@ -1812,7 +1897,13 @@ namespace Frida {
 			if (connection_closed)
 				return;
 			connection_closed = true;
-			channel = null;
+
+			if (channel != null) {
+				channel.invocation.disconnect (on_channel_invocation);
+				channel.notification.disconnect (on_channel_notification);
+				channel = null;
+			}
+
 			close ();
 		}
 
@@ -2026,7 +2117,7 @@ namespace Frida {
 		}
 	}
 
-	private sealed class XpcService : Object, Service {
+	private sealed class XpcServiceSession : Object, ServiceSession {
 		public Fruity.XpcConnection connection {
 			get;
 			construct;
@@ -2040,7 +2131,7 @@ namespace Frida {
 			ACTIVE,
 		}
 
-		public XpcService (Fruity.XpcConnection connection) {
+		public XpcServiceSession (Fruity.XpcConnection connection) {
 			Object (connection: connection);
 		}
 
@@ -2049,8 +2140,11 @@ namespace Frida {
 			connection.message.connect (on_message);
 		}
 
-		public bool is_closed () {
-			return connection_closed;
+		~XpcServiceSession () {
+			connection.close.disconnect (on_close);
+			connection.message.disconnect (on_message);
+
+			connection.cancel ();
 		}
 
 		public async void activate (Cancellable? cancellable) throws Error, IOError {
@@ -2058,20 +2152,21 @@ namespace Frida {
 		}
 
 		private void ensure_active () throws Error {
+			if (connection_closed)
+				throw new Error.INVALID_OPERATION ("Service is closed");
+
 			if (state == INACTIVE) {
 				state = ACTIVE;
 
-				if (connection_closed) {
-					close ();
-					throw new Error.INVALID_OPERATION ("Service is closed");
-				}
-
 				connection.activate ();
 			}
 		}
 
 		public async void cancel (Cancellable? cancellable) throws IOError {
-			connection.cancel ();
+			if (state == ACTIVE)
+				connection.cancel ();
+			else if (!connection_closed)
+				on_close (null);
 		}
 
 		public async Variant request (Variant parameters, Cancellable? cancellable = null) throws Error, IOError {
@@ -2095,6 +2190,7 @@ namespace Frida {
 
 		private void on_close (Error? error) {
 			connection_closed = true;
+
 			close ();
 		}
 

src/fruity/injector.vala

@@ -6,7 +6,7 @@ namespace Frida.Fruity.Injector {
 		return yield session.run (cancellable);
 	}
 
-	public class GadgetDetails : Object {
+	public sealed class GadgetDetails : Object {
 		public uint16 port {
 			get;
 			construct;
@@ -21,7 +21,7 @@ namespace Frida.Fruity.Injector {
 		UNSUPPORTED
 	}
 
-	private class Session : Object {
+	private sealed class Session : Object {
 		public Gum.DarwinModule module {
 			get;
 			construct;

src/fruity/installation-proxy.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class InstallationProxyClient : Object, AsyncInitable {
+	public sealed class InstallationProxyClient : Object, AsyncInitable {
 		public Device device {
 			get;
 			construct;
@@ -193,7 +193,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class ApplicationDetails : Object {
+	public sealed class ApplicationDetails : Object {
 		public string identifier {
 			get;
 			construct;

src/fruity/keyed-archive.vala

@@ -22,7 +22,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSNumber : NSObject {
+	public sealed class NSNumber : NSObject {
 		public Kind kind {
 			get;
 			private set;
@@ -108,7 +108,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSString : NSObject {
+	public sealed class NSString : NSObject {
 		public string str {
 			get;
 			private set;
@@ -134,7 +134,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSData : NSObject {
+	public sealed class NSData : NSObject {
 		public Bytes bytes {
 			get;
 			private set;
@@ -160,7 +160,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSDictionary : NSObject {
+	public sealed class NSDictionary : NSObject {
 		public int size {
 			get {
 				return storage.size;
@@ -221,7 +221,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSDictionaryRaw : NSObject {
+	public sealed class NSDictionaryRaw : NSObject {
 		public int size {
 			get {
 				return storage.size;
@@ -255,7 +255,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSArray : NSObject {
+	public sealed class NSArray : NSObject {
 		public int length {
 			get {
 				return storage.size;
@@ -279,7 +279,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSDate : NSObject {
+	public sealed class NSDate : NSObject {
 		public double time {
 			get;
 			private set;
@@ -298,7 +298,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class NSError : NSObject {
+	public sealed class NSError : NSObject {
 		public NSString domain {
 			get;
 			private set;
@@ -321,7 +321,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class DTTapMessage : NSObject {
+	public sealed class DTTapMessage : NSObject {
 		public NSDictionary plist {
 			get;
 			private set;
@@ -658,7 +658,7 @@ namespace Frida.Fruity {
 			return new DTTapMessage ((NSDictionary) decode_value (instance.get_uid ("DTTapMessagePlist"), ctx));
 		}
 
-		private class EncodingContext {
+		private sealed class EncodingContext {
 			public PlistArray objects;
 
 			private Gee.HashMap<string, PlistUid> classes = new Gee.HashMap<string, PlistUid> ();
@@ -709,7 +709,7 @@ namespace Frida.Fruity {
 			}
 		}
 
-		private class DecodingContext {
+		private sealed class DecodingContext {
 			public PlistArray objects;
 
 			public DecodingContext (PlistArray objects) {

src/fruity/lldb.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaLLDB", gir_version = "1.0")]
 namespace Frida.LLDB {
-	public class Client : GDB.Client {
+	public sealed class Client : GDB.Client {
 		public Process? process {
 			get {
 				return _process;
@@ -438,7 +438,7 @@ namespace Frida.LLDB {
 		}
 	}
 
-	public class LaunchOptions : Object {
+	public sealed class LaunchOptions : Object {
 		public string[] env {
 			get;
 			set;
@@ -457,7 +457,7 @@ namespace Frida.LLDB {
 		}
 	}
 
-	public class Process : Object {
+	public sealed class Process : Object {
 		public uint pid {
 			get;
 			set;
@@ -556,7 +556,7 @@ namespace Frida.LLDB {
 		ARM64E		= 2,
 	}
 
-	public class Thread : GDB.Thread {
+	public sealed class Thread : GDB.Thread {
 		private const uint PAGE_SIZE = 16384U;
 		private const uint32 THREAD_MAGIC = 0x54485244U;
 
@@ -656,7 +656,7 @@ namespace Frida.LLDB {
 			return address & ~((uint64) (PAGE_SIZE - 1));
 		}
 
-		public class Snapshot {
+		public sealed class Snapshot {
 			public uint handle {
 				get;
 				private set;
@@ -667,7 +667,7 @@ namespace Frida.LLDB {
 			}
 		}
 
-		public class Frame {
+		public sealed class Frame {
 			public uint64 address {
 				get;
 				private set;
@@ -695,7 +695,7 @@ namespace Frida.LLDB {
 		}
 	}
 
-	public class Module : Object {
+	public sealed class Module : Object {
 		public uint64 load_address {
 			get;
 			construct;
@@ -719,7 +719,7 @@ namespace Frida.LLDB {
 			);
 		}
 
-		public class Segment {
+		public sealed class Segment {
 			public string name;
 
 			public uint64 vmaddr;
@@ -730,7 +730,7 @@ namespace Frida.LLDB {
 		}
 	}
 
-	public class Exception : GDB.Exception {
+	public sealed class Exception : GDB.Exception {
 		public MachExceptionType metype {
 			get;
 			construct;
@@ -896,7 +896,7 @@ namespace Frida.LLDB {
 		}
 	}
 
-	public class AppleDyldFields : Object {
+	public sealed class AppleDyldFields : Object {
 		public uint64 all_image_info {
 			get;
 			construct;

src/fruity/lockdown.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class LockdownClient : Object {
+	public sealed class LockdownClient : Object {
 		public signal void closed ();
 
 		public PlistServiceClient service {

src/fruity/ncm.vala

@@ -411,7 +411,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	internal class UsbNcmConfig {
+	internal sealed class UsbNcmConfig {
 		public uint8 ctrl_iface;
 		public uint8 data_iface;
 		public int data_altsetting;

src/fruity/network-stack.vala

@@ -196,7 +196,7 @@ namespace Frida.Fruity {
 			STOPPED
 		}
 
-		public class VirtualNetworkStack (Bytes? ethernet_address, InetAddress? ipv6_address, uint16 mtu) {
+		public VirtualNetworkStack (Bytes? ethernet_address, InetAddress? ipv6_address, uint16 mtu) {
 			Object (
 				ethernet_address: ethernet_address,
 				ipv6_address: ipv6_address,
@@ -394,7 +394,7 @@ namespace Frida.Fruity {
 			source.attach (main_context);
 		}
 
-		private class TcpConnection : IOStream, AsyncInitable {
+		private class TcpConnection : VirtualStream, AsyncInitable {
 			public VirtualNetworkStack netstack {
 				get;
 				construct;
@@ -405,53 +405,13 @@ namespace Frida.Fruity {
 				construct;
 			}
 
-			public State state {
-				get {
-					return _state;
-				}
-			}
-
-			public override InputStream input_stream {
-				get {
-					return _input_stream;
-				}
-			}
-
-			public override OutputStream output_stream {
-				get {
-					return _output_stream;
-				}
-			}
-
-			public IOCondition pending_io {
-				get {
-					lock (state)
-						return events;
-				}
-			}
-
 			private Promise<bool> established = new Promise<bool> ();
 
-			private State _state = OPENING;
-			private TcpInputStream _input_stream;
-			private TcpOutputStream _output_stream;
-
 			private unowned LWIP.TcpPcb? pcb;
-			private IOCondition events = 0;
 			private ByteArray rx_buf = new ByteArray.sized (64 * 1024);
 			private ByteArray tx_buf = new ByteArray.sized (64 * 1024);
 			private size_t tx_space_available = 0;
 
-			private Gee.Map<unowned Source, IOCondition> sources = new Gee.HashMap<unowned Source, IOCondition> ();
-
-			private MainContext main_context;
-
-			public enum State {
-				OPENING,
-				OPENED,
-				CLOSED
-			}
-
 			public static async TcpConnection open (VirtualNetworkStack netstack, InetSocketAddress address,
 					Cancellable? cancellable) throws Error, IOError {
 				var connection = new TcpConnection (netstack, address);
@@ -469,22 +429,28 @@ namespace Frida.Fruity {
 				Object (netstack: netstack, address: address);
 			}
 
-			construct {
-				_input_stream = new TcpInputStream (this);
-				_output_stream = new TcpOutputStream (this);
-
-				main_context = MainContext.ref_thread_default ();
-			}
-
 			public override void dispose () {
-				_output_stream.detach ();
-				_input_stream.detach ();
-
 				stop ();
 
 				base.dispose ();
 			}
 
+			protected override VirtualStream.State query_initial_state () {
+				return OPENING;
+			}
+
+			protected override IOCondition query_events () {
+				IOCondition new_events = 0;
+
+				if (rx_buf.len != 0 || state == CLOSED)
+					new_events |= IN;
+
+				if (tx_space_available != 0)
+					new_events |= OUT;
+
+				return new_events;
+			}
+
 			private async bool init_async (int io_priority, Cancellable? cancellable) throws Error, IOError {
 				LWIP.Runtime.schedule (do_start);
 
@@ -547,8 +513,8 @@ namespace Frida.Fruity {
 					return OK;
 				});
 
-				_state = CLOSED;
-				update_events ();
+				state = CLOSED;
+				update_pending_io ();
 			}
 
 			private void detach_from_pcb () {
@@ -557,12 +523,13 @@ namespace Frida.Fruity {
 			}
 
 			private void on_connect () {
-				lock (state)
+				with_state_lock (() => {
 					tx_space_available = pcb.query_available_send_buffer_space ();
-				update_events ();
+				});
+				update_pending_io ();
 
 				schedule_on_frida_thread (() => {
-					_state = OPENED;
+					state = OPEN;
 
 					if (!established.future.ready)
 						established.resolve (true);
@@ -575,8 +542,8 @@ namespace Frida.Fruity {
 				if (pbuf == null) {
 					detach_from_pcb ();
 					schedule_on_frida_thread (() => {
-						_state = CLOSED;
-						update_events ();
+						state = CLOSED;
+						update_pending_io ();
 						return Source.REMOVE;
 					});
 					return;
@@ -584,15 +551,17 @@ namespace Frida.Fruity {
 
 				var buffer = new uint8[pbuf.tot_len];
 				unowned uint8[] chunk = pbuf.get_contiguous (buffer, pbuf.tot_len);
-				lock (state)
+				with_state_lock (() => {
 					rx_buf.append (chunk[:pbuf.tot_len]);
-				update_events ();
+				});
+				update_pending_io ();
 			}
 
 			private void on_sent (uint16 len) {
-				lock (state)
+				with_state_lock (() => {
 					tx_space_available = pcb.query_available_send_buffer_space () - tx_buf.len;
-				update_events ();
+				});
+				update_pending_io ();
 			}
 
 			private void on_error (LWIP.ErrorCode err) {
@@ -602,8 +571,8 @@ namespace Frida.Fruity {
 				else
 					detach_from_pcb ();
 				schedule_on_frida_thread (() => {
-					_state = CLOSED;
-					update_events ();
+					state = CLOSED;
+					update_pending_io ();
 
 					if (!established.future.ready)
 						established.reject (parse_error (err));
@@ -612,17 +581,11 @@ namespace Frida.Fruity {
 				});
 			}
 
-			public override bool close (GLib.Cancellable? cancellable) throws IOError {
+			protected override void handle_close () {
 				stop ();
-				return true;
 			}
 
-			public override async bool close_async (int io_priority, GLib.Cancellable? cancellable) throws IOError {
-				stop ();
-				return true;
-			}
-
-			public void shutdown_rx () throws IOError {
+			public override void shutdown_read () throws IOError {
 				check_io (netstack.perform_on_lwip_thread (() => {
 					if (pcb == null)
 						return OK;
@@ -630,7 +593,7 @@ namespace Frida.Fruity {
 				}));
 			}
 
-			public void shutdown_tx () throws IOError {
+			public override void shutdown_write () throws IOError {
 				check_io (netstack.perform_on_lwip_thread (() => {
 					if (pcb == null)
 						return OK;
@@ -638,17 +601,19 @@ namespace Frida.Fruity {
 				}));
 			}
 
-			public ssize_t recv (uint8[] buffer) throws IOError {
+			public override ssize_t read (uint8[] buffer) throws IOError {
 				ssize_t n = 0;
 
 				netstack.perform_on_lwip_thread (() => {
-					lock (state) {
+					with_state_lock (() => {
 						n = ssize_t.min (buffer.length, rx_buf.len);
 						if (n == 0)
-							return OK;
+							return;
 						Memory.copy (buffer, rx_buf.data, n);
 						rx_buf.remove_range (0, (uint) n);
-					}
+					});
+					if (n == 0)
+						return OK;
 
 					if (pcb == null)
 						return OK;
@@ -664,41 +629,43 @@ namespace Frida.Fruity {
 				});
 
 				if (n == 0) {
-					if (_state == CLOSED)
+					if (state == CLOSED)
 						return 0;
 					throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
 				}
 
-				update_events ();
+				update_pending_io ();
 
 				return n;
 			}
 
-			public ssize_t send (uint8[] buffer) throws IOError {
+			public override ssize_t write (uint8[] buffer) throws IOError {
 				ssize_t n = 0;
 
 				netstack.perform_on_lwip_thread (() => {
 					if (pcb == null)
 						return OK;
 
-					lock (state) {
+					with_state_lock (() => {
 						n = ssize_t.min (buffer.length, (ssize_t) tx_space_available);
 						if (n == 0)
-							return OK;
+							return;
 						tx_buf.append (buffer[:n]);
 						tx_space_available -= n;
-					}
+					});
+					if (n == 0)
+						return OK;
 
 					size_t available_space = pcb.query_available_send_buffer_space ();
 
 					uint8[]? data = null;
-					lock (state) {
+					with_state_lock (() => {
 						size_t num_bytes_to_write = size_t.min (tx_buf.len, available_space);
 						if (num_bytes_to_write != 0) {
 							data = tx_buf.data[:num_bytes_to_write];
 							tx_buf.remove_range (0, (uint) num_bytes_to_write);
 						}
-					}
+					});
 					if (data == null)
 						return OK;
 
@@ -706,8 +673,9 @@ namespace Frida.Fruity {
 					pcb.output ();
 
 					available_space = pcb.query_available_send_buffer_space ();
-					lock (state)
+					with_state_lock (() => {
 						tx_space_available = available_space - tx_buf.len;
+					});
 
 					return OK;
 				});
@@ -715,44 +683,11 @@ namespace Frida.Fruity {
 				if (n == 0)
 					throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
 
-				update_events ();
+				update_pending_io ();
 
 				return n;
 			}
 
-			public void register_source (Source source, IOCondition condition) {
-				lock (state)
-					sources[source] = condition | IOCondition.ERR | IOCondition.HUP;
-			}
-
-			public void unregister_source (Source source) {
-				lock (state)
-					sources.unset (source);
-			}
-
-			private void update_events () {
-				lock (state) {
-					IOCondition new_events = 0;
-
-					if (rx_buf.len != 0 || _state == CLOSED)
-						new_events |= IN;
-
-					if (tx_space_available != 0)
-						new_events |= OUT;
-
-					events = new_events;
-
-					foreach (var entry in sources.entries) {
-						unowned Source source = entry.key;
-						IOCondition c = entry.value;
-						if ((new_events & c) != 0)
-							source.set_ready_time (0);
-					}
-				}
-
-				notify_property ("pending-io");
-			}
-
 			private void schedule_on_frida_thread (owned SourceFunc function) {
 				var source = new IdleSource ();
 				source.set_callback ((owned) function);
@@ -760,201 +695,6 @@ namespace Frida.Fruity {
 			}
 		}
 
-		private class TcpInputStream : InputStream, PollableInputStream {
-			private weak TcpConnection connection;
-
-			public TcpInputStream (TcpConnection connection) {
-				Object ();
-				this.connection = connection;
-			}
-
-			internal void detach () {
-				connection = null;
-			}
-
-			public override bool close (Cancellable? cancellable) throws IOError {
-				if (connection != null)
-					connection.shutdown_rx ();
-				return true;
-			}
-
-			public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-				return close (cancellable);
-			}
-
-			public override ssize_t read (uint8[] buffer, Cancellable? cancellable) throws IOError {
-				if (connection == null)
-					return 0;
-
-				if (!is_readable ()) {
-					bool done = false;
-					var mutex = Mutex ();
-					var cond = Cond ();
-
-					ulong io_handler = connection.notify["pending-io"].connect ((obj, pspec) => {
-						if (is_readable ()) {
-							mutex.lock ();
-							done = true;
-							cond.signal ();
-							mutex.unlock ();
-						}
-					});
-					ulong cancellation_handler = 0;
-					if (cancellable != null) {
-						cancellation_handler = cancellable.connect (() => {
-							mutex.lock ();
-							done = true;
-							cond.signal ();
-							mutex.unlock ();
-						});
-					}
-
-					if (!is_readable ()) {
-						mutex.lock ();
-						while (!done)
-							cond.wait (mutex);
-						mutex.unlock ();
-					}
-
-					if (cancellation_handler != 0)
-						cancellable.disconnect (cancellation_handler);
-					connection.disconnect (io_handler);
-
-					cancellable.set_error_if_cancelled ();
-				}
-
-				return connection.recv (buffer);
-			}
-
-			public bool can_poll () {
-				return true;
-			}
-
-			public bool is_readable () {
-				if (connection == null)
-					return true;
-				return (connection.pending_io & IOCondition.IN) != 0;
-			}
-
-			public PollableSource create_source (Cancellable? cancellable) {
-				return new PollableSource.full (this, new TcpIOSource (connection, IOCondition.IN), cancellable);
-			}
-
-			public ssize_t read_nonblocking_fn (uint8[] buffer) throws GLib.Error {
-				if (connection == null)
-					return 0;
-				return connection.recv (buffer);
-			}
-		}
-
-		private class TcpOutputStream : OutputStream, PollableOutputStream {
-			private weak TcpConnection? connection;
-
-			public TcpOutputStream (TcpConnection connection) {
-				Object ();
-				this.connection = connection;
-			}
-
-			internal void detach () {
-				connection = null;
-			}
-
-			public override bool close (Cancellable? cancellable) throws IOError {
-				if (connection != null)
-					connection.shutdown_tx ();
-				return true;
-			}
-
-			public override async bool close_async (int io_priority, Cancellable? cancellable) throws GLib.IOError {
-				return close (cancellable);
-			}
-
-			public override bool flush (GLib.Cancellable? cancellable) throws GLib.Error {
-				return true;
-			}
-
-			public override async bool flush_async (int io_priority, GLib.Cancellable? cancellable) throws GLib.Error {
-				return true;
-			}
-
-			public override ssize_t write (uint8[] buffer, Cancellable? cancellable) throws IOError {
-				assert_not_reached ();
-			}
-
-			public bool can_poll () {
-				return true;
-			}
-
-			public bool is_writable () {
-				if (connection == null)
-					return false;
-				return (connection.pending_io & IOCondition.OUT) != 0;
-			}
-
-			public PollableSource create_source (Cancellable? cancellable) {
-				return new PollableSource.full (this, new TcpIOSource (connection, IOCondition.OUT), cancellable);
-			}
-
-			public ssize_t write_nonblocking_fn (uint8[]? buffer) throws GLib.Error {
-				if (connection == null)
-					throw new IOError.CLOSED ("Connection is closed");
-				return connection.send (buffer);
-			}
-
-			public PollableReturn writev_nonblocking_fn (OutputVector[] vectors, out size_t bytes_written) throws GLib.Error {
-				assert_not_reached ();
-			}
-		}
-
-		private class TcpIOSource : Source {
-			public TcpConnection connection;
-			public IOCondition condition;
-
-			public TcpIOSource (TcpConnection? connection, IOCondition condition) {
-				this.connection = connection;
-				this.condition = condition;
-
-				if (connection != null)
-					connection.register_source (this, condition);
-			}
-
-			~TcpIOSource () {
-				if (connection != null)
-					connection.unregister_source (this);
-			}
-
-			protected override bool prepare (out int timeout) {
-				timeout = -1;
-				return is_ready ();
-			}
-
-			protected override bool check () {
-				return is_ready ();
-			}
-
-			private bool is_ready () {
-				IOCondition pending_io = (connection != null) ? connection.pending_io : IOCondition.IN;
-				return (pending_io & condition) != 0;
-			}
-
-			protected override bool dispatch (SourceFunc? callback) {
-				set_ready_time (-1);
-
-				if (callback == null)
-					return Source.REMOVE;
-
-				return callback ();
-			}
-
-			protected static bool closure_callback (Closure closure) {
-				var return_value = Value (typeof (bool));
-
-				closure.invoke (ref return_value, {});
-
-				return return_value.get_boolean ();
-			}
-		}
-
 		private class Ipv6UdpSocket : Object, UdpSocket, DatagramBased {
 			public VirtualNetworkStack netstack {
 				get;
@@ -969,13 +709,13 @@ namespace Frida.Fruity {
 
 			public IOCondition pending_io {
 				get {
-					lock (events)
-						return events;
+					lock (_pending_io)
+						return _pending_io;
 				}
 			}
 
 			private unowned LWIP.UdpPcb? pcb;
-			private IOCondition events = OUT;
+			private IOCondition _pending_io = OUT;
 			private Gee.Queue<Packet> rx_queue = new Gee.ArrayQueue<Packet> ();
 
 			private Gee.Map<unowned Source, IOCondition> sources = new Gee.HashMap<unowned Source, IOCondition> ();
@@ -1011,9 +751,9 @@ namespace Frida.Fruity {
 				var sender = ip6_address_to_inet_socket_address (addr, port);
 				var packet = new Packet (bytes, sender);
 
-				lock (events)
+				lock (pending_io)
 					rx_queue.offer (packet);
-				update_events ();
+				update_pending_io ();
 			}
 
 			public void bind (InetSocketAddress address) throws Error {
@@ -1047,14 +787,14 @@ namespace Frida.Fruity {
 				int received;
 				for (received = 0; received != messages.length; received++) {
 					Packet? packet;
-					lock (events)
+					lock (pending_io)
 						packet = rx_queue.poll ();
 					if (packet == null) {
 						if (received == 0)
 							throw new IOError.WOULD_BLOCK ("Resource temporarily unavailable");
 						break;
 					}
-					update_events ();
+					update_pending_io ();
 
 					if (messages[received].address != null)
 						*messages[received].address = packet.address.ref ();
@@ -1133,28 +873,26 @@ namespace Frida.Fruity {
 			}
 
 			public void register_source (Source source, IOCondition condition) {
-				lock (events)
+				lock (pending_io)
 					sources[source] = condition | IOCondition.ERR | IOCondition.HUP;
 			}
 
 			public void unregister_source (Source source) {
-				lock (events)
+				lock (pending_io)
 					sources.unset (source);
 			}
 
-			private void update_events () {
-				lock (events) {
-					IOCondition new_events = OUT;
+			private void update_pending_io () {
+				lock (pending_io) {
+					_pending_io = OUT;
 
 					if (!rx_queue.is_empty)
-						new_events |= IN;
-
-					events = new_events;
+						_pending_io |= IN;
 
 					foreach (var entry in sources.entries) {
 						unowned Source source = entry.key;
 						IOCondition c = entry.value;
-						if ((new_events & c) != 0)
+						if ((_pending_io & c) != 0)
 							source.set_ready_time (0);
 					}
 				}

src/fruity/opack.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class OpackBuilder {
+	public sealed class OpackBuilder {
 		protected BufferBuilder builder = new BufferBuilder (LITTLE_ENDIAN);
 		private Gee.Deque<Scope> scopes = new Gee.ArrayQueue<Scope> ();
 
@@ -132,7 +132,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class OpackParser {
+	public sealed class OpackParser {
 		private BufferReader reader;
 
 		[Flags]

src/fruity/plist-service.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class PlistServiceClient : Object {
+	public sealed class PlistServiceClient : Object {
 		public signal void closed ();
 
 		public IOStream stream {

src/fruity/plist.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class Plist : PlistDict {
+	public sealed class Plist : PlistDict {
 		public enum Format {
 			AUTO,
 			BINARY,
@@ -1355,7 +1355,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PlistArray : Object {
+	public sealed class PlistArray : Object {
 		public bool is_empty {
 			get {
 				return storage.is_empty;
@@ -1511,10 +1511,10 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PlistNull : Object {
+	public sealed class PlistNull : Object {
 	}
 
-	public class PlistDate : Object {
+	public sealed class PlistDate : Object {
 		private DateTime time;
 
 		public PlistDate (DateTime time) {
@@ -1526,7 +1526,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PlistUid : Object {
+	public sealed class PlistUid : Object {
 		public uint64 uid {
 			get;
 			construct;

src/fruity/springboard-services.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class SpringboardServicesClient : Object, AsyncInitable {
+	public sealed class SpringboardServicesClient : Object, AsyncInitable {
 		public Device device {
 			get;
 			construct;

src/fruity/usbmux.vala

@@ -1,6 +1,6 @@
 [CCode (gir_namespace = "FridaFruity", gir_version = "1.0")]
 namespace Frida.Fruity {
-	public class UsbmuxClient : Object, AsyncInitable {
+	public sealed class UsbmuxClient : Object, AsyncInitable {
 		public signal void device_attached (UsbmuxDevice device);
 		public signal void device_detached (UsbmuxDevice device);
 
@@ -548,7 +548,7 @@ namespace Frida.Fruity {
 		PROTOCOL
 	}
 
-	public class UsbmuxDevice : Object {
+	public sealed class UsbmuxDevice : Object {
 		public ConnectionType connection_type {
 			get;
 			construct;

src/fruity/xpc.vala

@@ -3,7 +3,7 @@ namespace Frida.Fruity {
 	using OpenSSL;
 	using OpenSSL.Envelope;
 
-	public class DiscoveryService : Object, AsyncInitable {
+	public sealed class DiscoveryService : Object, AsyncInitable {
 		public IOStream stream {
 			get;
 			construct;
@@ -119,11 +119,11 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class ServiceInfo {
+	public sealed class ServiceInfo {
 		public uint16 port;
 	}
 
-	public class PairingService : Object, AsyncInitable {
+	public sealed class PairingService : Object, AsyncInitable {
 		public const string DNS_SD_NAME = "_remotepairing._tcp.local";
 
 		public PairingTransport transport {
@@ -1248,7 +1248,7 @@ namespace Frida.Fruity {
 		public abstract void post (Bytes message);
 	}
 
-	public class XpcPairingTransport : Object, PairingTransport {
+	public sealed class XpcPairingTransport : Object, PairingTransport {
 		public IOStream stream {
 			get;
 			construct;
@@ -1320,7 +1320,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PlainPairingTransport : Object, PairingTransport {
+	public sealed class PlainPairingTransport : Object, PairingTransport {
 		public IOStream stream {
 			get;
 			construct;
@@ -1458,7 +1458,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PairingStore {
+	public sealed class PairingStore {
 		public PairingIdentity self_identity {
 			get {
 				return _self_identity;
@@ -1664,7 +1664,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PairingIdentity {
+	public sealed class PairingIdentity {
 		public string identifier;
 		public Key key;
 		public Bytes irk;
@@ -1681,7 +1681,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PairingPeer {
+	public sealed class PairingPeer {
 		public string identifier;
 		public Bytes public_key;
 		public Bytes irk;
@@ -1692,7 +1692,7 @@ namespace Frida.Fruity {
 		public Bytes? remote_unlock_host_key;
 	}
 
-	public class PairingServiceMetadata {
+	public sealed class PairingServiceMetadata {
 		public string identifier;
 		public Bytes auth_tag;
 
@@ -1721,7 +1721,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class DeviceOptions {
+	public sealed class DeviceOptions {
 		public bool allows_pair_setup;
 		public bool allows_pinless_pairing;
 		public bool allows_promptless_automation_pairing_upgrade;
@@ -1729,7 +1729,7 @@ namespace Frida.Fruity {
 		public bool allows_incoming_tunnel_connections;
 	}
 
-	public class DeviceInfo {
+	public sealed class DeviceInfo {
 		public string name;
 		public string model;
 		public string udid;
@@ -1737,7 +1737,7 @@ namespace Frida.Fruity {
 		public Plist kvs;
 	}
 
-	private class PairingParamsBuilder {
+	private sealed class PairingParamsBuilder {
 		private BufferBuilder builder = new BufferBuilder (LITTLE_ENDIAN);
 
 		public unowned PairingParamsBuilder add_method (uint8 method) {
@@ -1810,7 +1810,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	private class PairingParamsParser {
+	private sealed class PairingParamsParser {
 		private BufferReader reader;
 		private EnumClass param_type_class;
 
@@ -1946,7 +1946,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class TunnelParameters {
+	public sealed class TunnelParameters {
 		public InetAddress address;
 		public uint16 mtu;
 		public InetAddress server_address;
@@ -2877,7 +2877,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class AppService : TrustedService {
+	public sealed class AppService : TrustedService {
 		public static async AppService open (IOStream stream, Cancellable? cancellable = null) throws Error, IOError {
 			var service = new AppService (stream);
 
@@ -3036,7 +3036,7 @@ namespace Frida.Fruity {
 			return processes;
 		}
 
-		public class ApplicationInfo {
+		public sealed class ApplicationInfo {
 			public string bundle_identifier;
 			public string? bundle_version;
 			public string name;
@@ -3050,7 +3050,7 @@ namespace Frida.Fruity {
 			public bool is_app_clip;
 		}
 
-		public class ProcessInfo {
+		public sealed class ProcessInfo {
 			public uint pid;
 			public string path;
 		}
@@ -3707,11 +3707,11 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class PeerInfo {
+	public sealed class PeerInfo {
 		public Variant? metadata;
 	}
 
-	public class XpcMessageBuilder : Object {
+	public sealed class XpcMessageBuilder : Object {
 		private MessageType message_type;
 		private MessageFlags message_flags = NONE;
 		private uint64 message_id = 0;
@@ -3752,7 +3752,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class XpcMessage {
+	public sealed class XpcMessage {
 		public MessageType type;
 		public MessageFlags flags;
 		public uint64 id;
@@ -3871,7 +3871,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	public class XpcBodyBuilder : XpcObjectBuilder {
+	public sealed class XpcBodyBuilder : XpcObjectBuilder {
 		public XpcBodyBuilder () {
 			base ();
 
@@ -4066,7 +4066,7 @@ namespace Frida.Fruity {
 		DICTIONARY	= 0xf000,
 	}
 
-	private class XpcBodyParser {
+	private sealed class XpcBodyParser {
 		public static Variant parse (uint8[] data) throws Error {
 			if (data.length < 12)
 				throw new Error.INVALID_ARGUMENT ("Invalid xpc_object: truncated");
@@ -4086,7 +4086,7 @@ namespace Frida.Fruity {
 		}
 	}
 
-	private class XpcObjectParser {
+	private sealed class XpcObjectParser {
 		private Buffer buf;
 		private size_t cursor;
 		private EnumClass object_type_class;

src/gdb.vala

@@ -1087,7 +1087,7 @@ namespace Frida.GDB {
 			return sum;
 		}
 
-		public class Packet {
+		public sealed class Packet {
 			public const size_t OVERHEAD = 1 + 1 + 2;
 
 			public string payload {
@@ -1106,7 +1106,7 @@ namespace Frida.GDB {
 			}
 		}
 
-		public class PacketBuilder {
+		public sealed class PacketBuilder {
 			private StringBuilder? buffer;
 			private size_t initial_capacity;
 			private ChecksumType checksum_type;
@@ -1727,7 +1727,7 @@ namespace Frida.GDB {
 		}
 	}
 
-	public class Breakpoint : Object {
+	public sealed class Breakpoint : Object {
 		public signal void removed ();
 
 		public Kind kind {

src/host-session-service.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class HostSessionService : Object {
+	public sealed class HostSessionService : Object {
 		private Gee.ArrayList<HostSessionBackend> backends = new Gee.ArrayList<HostSessionBackend> ();
 
 		public signal void provider_available (HostSessionProvider provider);
@@ -168,7 +168,16 @@ namespace Frida {
 
 		public abstract async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
 			Cancellable? cancellable = null) throws Error, IOError;
+		public abstract void unlink_agent_session (HostSession host_session, AgentSessionId id);
 		public signal void agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash);
+
+		public abstract async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable = null)
+			throws Error, IOError;
+		public abstract void unlink_channel (HostSession host_session, ChannelId id);
+
+		public abstract async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id,
+			Cancellable? cancellable = null) throws Error, IOError;
+		public abstract void unlink_service_session (HostSession host_session, ServiceSessionId id);
 	}
 
 	public enum HostSessionProviderKind {
@@ -177,7 +186,7 @@ namespace Frida {
 		USB
 	}
 
-	public class HostSessionOptions : Object {
+	public sealed class HostSessionOptions : Object {
 		public Gee.Map<string, Value?> map {
 			get;
 			set;
@@ -189,10 +198,6 @@ namespace Frida {
 		public abstract async IOStream open_channel (string address, Cancellable? cancellable = null) throws Error, IOError;
 	}
 
-	public interface HostServiceProvider : Object {
-		public abstract async Service open_service (string address, Cancellable? cancellable = null) throws Error, IOError;
-	}
-
 	public interface Pairable : Object {
 		public abstract async void unpair (Cancellable? cancellable = null) throws Error, IOError;
 	}
@@ -205,7 +210,129 @@ namespace Frida {
 		public abstract async void stop (Cancellable? cancellable = null) throws IOError;
 	}
 
-	public abstract class BaseDBusHostSession : Object, HostSession, AgentController {
+	public abstract class LocalHostSessionBackend : Object, HostSessionBackend {
+		private LocalHostSessionProvider local_provider;
+
+		public async void start (Cancellable? cancellable) throws IOError {
+			assert (local_provider == null);
+			local_provider = make_provider ();
+
+			provider_available (local_provider);
+		}
+
+		public async void stop (Cancellable? cancellable) throws IOError {
+			assert (local_provider != null);
+
+			provider_unavailable (local_provider);
+
+			yield local_provider.close (cancellable);
+			local_provider = null;
+		}
+
+		protected abstract LocalHostSessionProvider make_provider ();
+	}
+
+	public abstract class LocalHostSessionProvider : Object, HostSessionProvider {
+		public string id {
+			get { return "local"; }
+		}
+
+		public string name {
+			get { return "Local System"; }
+		}
+
+		public Variant? icon {
+			get { return _icon; }
+		}
+		private Variant? _icon;
+
+		public HostSessionProviderKind kind {
+			get { return HostSessionProviderKind.LOCAL; }
+		}
+
+		private LocalHostSession host_session;
+
+		construct {
+			_icon = load_icon ();
+		}
+
+		protected abstract LocalHostSession make_host_session (HostSessionOptions? options) throws Error;
+
+		protected void take_host_session (LocalHostSession session) {
+			host_session = session;
+			host_session.agent_session_detached.connect (on_agent_session_detached);
+		}
+
+		protected virtual Variant? load_icon () {
+			return null;
+		}
+
+		public async void close (Cancellable? cancellable) throws IOError {
+			if (host_session == null)
+				return;
+
+			host_session.agent_session_detached.disconnect (on_agent_session_detached);
+
+			yield host_session.close (cancellable);
+			host_session = null;
+		}
+
+		public async HostSession create (HostSessionOptions? options, Cancellable? cancellable) throws Error, IOError {
+			if (host_session != null)
+				throw new Error.INVALID_OPERATION ("Already created");
+
+			take_host_session (make_host_session (options));
+
+			return host_session;
+		}
+
+		public async void destroy (HostSession session, Cancellable? cancellable) throws Error, IOError {
+			if (session != host_session)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+
+			host_session.agent_session_detached.disconnect (on_agent_session_detached);
+
+			yield host_session.close (cancellable);
+			host_session = null;
+		}
+
+		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
+				Cancellable? cancellable) throws Error, IOError {
+			if (host_session != this.host_session)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+
+			return yield this.host_session.link_agent_session (id, sink, cancellable);
+		}
+
+		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+			if (host_session != this.host_session)
+				return;
+
+			this.host_session.unlink_agent_session (id);
+		}
+
+		public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+				throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+		}
+
+		public void unlink_channel (HostSession host_session, ChannelId id) {
+		}
+
+		public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id, Cancellable? cancellable)
+				throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
+		public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+		}
+
+		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
+			agent_session_detached (id, reason, crash);
+		}
+	}
+
+	public abstract class LocalHostSession : Object, HostSession, AgentController {
 		private Gee.HashMap<uint, Cancellable> pending_establish_ops = new Gee.HashMap<uint, Cancellable> ();
 
 		private Gee.HashMap<uint, Future<AgentEntry>> agent_entries = new Gee.HashMap<uint, Future<AgentEntry>> ();
@@ -770,6 +897,14 @@ namespace Frida {
 			return InjectorPayloadId (raw_id);
 		}
 
+		public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+		}
+
+		public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+			throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+		}
+
 #if !WINDOWS
 		public async HostChildId prepare_to_fork (uint parent_pid, Cancellable? cancellable, out uint parent_injectee_id,
 				out uint child_injectee_id, out GLib.Socket child_socket) throws Error, IOError {
@@ -1251,7 +1386,7 @@ namespace Frida {
 		}
 	}
 
-	internal class InstalledHelperFile : Object, HelperFile {
+	internal sealed class InstalledHelperFile : Object, HelperFile {
 		public string path {
 			owned get {
 				return installed_path;
@@ -1268,7 +1403,7 @@ namespace Frida {
 		}
 	}
 
-	internal class TemporaryHelperFile : Object, HelperFile {
+	internal sealed class TemporaryHelperFile : Object, HelperFile {
 		public string path {
 			owned get {
 				return file.path;
@@ -1288,7 +1423,7 @@ namespace Frida {
 	public abstract class InternalAgent : Object, AgentMessageSink, RpcPeer {
 		public signal void unloaded ();
 
-		public weak BaseDBusHostSession host_session {
+		public weak LocalHostSession host_session {
 			get;
 			construct;
 		}

src/linux/frida-helper-backend.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class LinuxHelperBackend : Object, LinuxHelper {
+	public sealed class LinuxHelperBackend : Object, LinuxHelper {
 		public signal void idle ();
 
 		public bool is_idle {
@@ -597,7 +597,7 @@ namespace Frida {
 		}
 	}
 
-	private class SpawnedProcess : Object {
+	private sealed class SpawnedProcess : Object {
 		public signal void terminated ();
 		public signal void output (int fd, uint8[] data);
 
@@ -703,7 +703,7 @@ namespace Frida {
 		}
 	}
 
-	private class StdioPipes : Object {
+	private sealed class StdioPipes : Object {
 		public FileDescriptor input {
 			get;
 			construct;
@@ -734,7 +734,7 @@ namespace Frida {
 		}
 	}
 
-	private class ExecTransitionSession : SeizeSession {
+	private sealed class ExecTransitionSession : SeizeSession {
 		private ExecTransitionSession (uint pid) {
 			Object (pid: pid, on_init: SeizeSession.InitBehavior.CONTINUE);
 		}
@@ -758,7 +758,7 @@ namespace Frida {
 		}
 	}
 
-	private class PausedSyscallSession : SeizeSession {
+	private sealed class PausedSyscallSession : SeizeSession {
 		private State state = PENDING;
 
 		private enum State {
@@ -843,7 +843,7 @@ namespace Frida {
 
 	private const uint64 SOCK_CLOEXEC = 0x80000;
 
-	private class InjectSession : SeizeSession {
+	private sealed class InjectSession : SeizeSession {
 		private static ProcMapsSoEntry local_libc;
 		private static uint64 mmap_offset;
 		private static uint64 munmap_offset;
@@ -1353,7 +1353,7 @@ namespace Frida {
 		}
 	}
 
-	public class InjectSpec {
+	public sealed class InjectSpec {
 		public FileDescriptorBased library_so {
 			get;
 			private set;
@@ -1392,7 +1392,7 @@ namespace Frida {
 		}
 	}
 
-	private class CleanupSession : SeizeSession {
+	private sealed class CleanupSession : SeizeSession {
 		private CleanupSession (uint pid) {
 			Object (pid: pid);
 		}
@@ -1415,7 +1415,7 @@ namespace Frida {
 		}
 	}
 
-	private class ThreadSuspendSession : SeizeSession {
+	private sealed class ThreadSuspendSession : SeizeSession {
 		private ThreadSuspendSession (uint pid, uint tid) {
 			Object (pid: pid, tid: tid);
 		}
@@ -1445,7 +1445,7 @@ namespace Frida {
 	}
 
 
-	private class BootstrapResult {
+	private sealed class BootstrapResult {
 		public HelperBootstrapContext context;
 		public HelperLibcApi libc;
 		public AllocatedStack allocated_stack;
@@ -1464,7 +1464,7 @@ namespace Frida {
 		RELAUNCH
 	}
 
-	private class RemoteAgent : Object {
+	private sealed class RemoteAgent : Object {
 		public uint pid {
 			get;
 			construct;
@@ -2272,7 +2272,7 @@ namespace Frida {
 		ALREADY_ATTACHED,
 	}
 
-	private class ProcessCodeSwapScope {
+	private sealed class ProcessCodeSwapScope {
 		private State state = INACTIVE;
 
 		private SeizeSession session;
@@ -2329,7 +2329,7 @@ namespace Frida {
 		}
 	}
 
-	private class ThreadSuspendScope {
+	private sealed class ThreadSuspendScope {
 		private State state = INACTIVE;
 
 		private uint pid;
@@ -2427,7 +2427,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteCallBuilder {
+	private sealed class RemoteCallBuilder {
 		private uint64 target;
 		private uint64[] args = {};
 		private GPRegs regs;
@@ -2478,7 +2478,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteCall {
+	private sealed class RemoteCall {
 		private SeizeSession session;
 		private uint64 target;
 		private uint64[] args;
@@ -2660,7 +2660,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteCallResult {
+	private sealed class RemoteCallResult {
 		public RemoteCallStatus status;
 		public int stop_signal;
 		public uint64 return_value;
@@ -3204,7 +3204,7 @@ namespace Frida {
 		}
 	}
 
-	public class PidFileDescriptor : FileDescriptor {
+	public sealed class PidFileDescriptor : FileDescriptor {
 		private uint pid;
 
 		private PidFileDescriptor (int fd, uint pid) {
@@ -3319,7 +3319,7 @@ namespace Frida {
 	}
 #endif
 
-	private class ProcMapsSoEntry {
+	private sealed class ProcMapsSoEntry {
 		public uint64 base_address;
 		public string path;
 		public string identity;

src/linux/frida-helper-process.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class LinuxHelperProcess : Object, LinuxHelper {
+	public sealed class LinuxHelperProcess : Object, LinuxHelper {
 		public TemporaryDirectory tempdir {
 			get;
 			construct;
@@ -246,7 +246,7 @@ namespace Frida {
 		}
 	}
 
-	private class HelperFactory {
+	private sealed class HelperFactory {
 		public signal void lost (LinuxHelper helper);
 		public signal void output (uint pid, int fd, uint8[] data);
 		public signal void uninjected (uint id);
@@ -457,7 +457,7 @@ namespace Frida {
 		}
 	}
 
-	private class HelperSession : Object, LinuxHelper {
+	private sealed class HelperSession : Object, LinuxHelper {
 		public LinuxRemoteHelper proxy {
 			get;
 			construct;
@@ -606,7 +606,7 @@ namespace Frida {
 		}
 	}
 
-	private class ResourceStore {
+	private sealed class ResourceStore {
 		public TemporaryDirectory tempdir {
 			get;
 			private set;
@@ -659,7 +659,7 @@ namespace Frida {
 #endif
 	}
 
-	private class MemoryHelperFile : Object, HelperFile {
+	private sealed class MemoryHelperFile : Object, HelperFile {
 		public FileDescriptor fd {
 			get;
 			construct;

src/linux/frida-helper-service.vala

@@ -9,7 +9,7 @@ namespace Frida {
 		return service.run ();
 	}
 
-	public class LinuxHelperService : Object, LinuxRemoteHelper {
+	public sealed class LinuxHelperService : Object, LinuxRemoteHelper {
 		public string parent_address {
 			get;
 			construct;

src/linux/linjector.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class Linjector : Object, Injector {
+	public sealed class Linjector : Object, Injector {
 		public LinuxHelper helper {
 			get;
 			construct;
@@ -158,7 +158,7 @@ namespace Frida {
 		SINGLETON
 	}
 
-	public class AgentDescriptor : Object {
+	public sealed class AgentDescriptor : Object {
 		public PathTemplate name_template {
 			get;
 			construct;
@@ -219,7 +219,7 @@ namespace Frida {
 		internal extern static Bytes _clone_so (Bytes so);
 	}
 
-	public class AgentResource : Object {
+	public sealed class AgentResource : Object {
 		public string name {
 			get;
 			construct;

src/linux/linux-host-session.vala

@@ -1,84 +1,18 @@
 namespace Frida {
-	public class LinuxHostSessionBackend : Object, HostSessionBackend {
-		private LinuxHostSessionProvider local_provider;
-
-		public async void start (Cancellable? cancellable) throws IOError {
-			assert (local_provider == null);
-			local_provider = new LinuxHostSessionProvider ();
-			provider_available (local_provider);
-		}
-
-		public async void stop (Cancellable? cancellable) throws IOError {
-			assert (local_provider != null);
-			provider_unavailable (local_provider);
-			yield local_provider.close (cancellable);
-			local_provider = null;
+	public sealed class LinuxHostSessionBackend : LocalHostSessionBackend {
+		protected override LocalHostSessionProvider make_provider () {
+			return new LinuxHostSessionProvider ();
 		}
 	}
 
-	public class LinuxHostSessionProvider : Object, HostSessionProvider {
-		public string id {
-			get { return "local"; }
-		}
-
-		public string name {
-			get { return "Local System"; }
-		}
-
-		public Variant? icon {
-			get { return null; }
-		}
-
-		public HostSessionProviderKind kind {
-			get { return HostSessionProviderKind.LOCAL; }
-		}
-
-		private LinuxHostSession host_session;
-
-		public async void close (Cancellable? cancellable) throws IOError {
-			if (host_session == null)
-				return;
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async HostSession create (HostSessionOptions? options, Cancellable? cancellable) throws Error, IOError {
-			if (host_session != null)
-				throw new Error.INVALID_OPERATION ("Already created");
-
+	public sealed class LinuxHostSessionProvider : LocalHostSessionProvider {
+		protected override LocalHostSession make_host_session (HostSessionOptions? options) throws Error {
 			var tempdir = new TemporaryDirectory ();
-
-			host_session = new LinuxHostSession (new LinuxHelperProcess (tempdir), tempdir);
-			host_session.agent_session_detached.connect (on_agent_session_detached);
-
-			return host_session;
-		}
-
-		public async void destroy (HostSession session, Cancellable? cancellable) throws Error, IOError {
-			if (session != host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
-				Cancellable? cancellable) throws Error, IOError {
-			if (host_session != this.host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			return yield this.host_session.link_agent_session (id, sink, cancellable);
-		}
-
-		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
-			agent_session_detached (id, reason, crash);
+			return new LinuxHostSession (new LinuxHelperProcess (tempdir), tempdir);
 		}
 	}
 
-	public class LinuxHostSession : BaseDBusHostSession {
+	public sealed class LinuxHostSession : LocalHostSession {
 		public LinuxHelper helper {
 			get;
 			construct;
@@ -508,7 +442,7 @@ namespace Frida {
 	}
 
 #if ANDROID
-	private class RoboLauncher : Object {
+	private sealed class RoboLauncher : Object {
 		public signal void spawn_added (HostSpawnInfo info);
 		public signal void spawn_removed (HostSpawnInfo info);
 
@@ -808,7 +742,7 @@ namespace Frida {
 		}
 	}
 
-	private class ZygoteAgent : InternalAgent {
+	private sealed class ZygoteAgent : InternalAgent {
 		public uint pid {
 			get;
 			construct;
@@ -861,7 +795,7 @@ namespace Frida {
 		}
 	}
 
-	private class SystemServerAgent : InternalAgent {
+	private sealed class SystemServerAgent : InternalAgent {
 		private delegate void CompletionNotify ();
 
 		public SystemServerAgent (LinuxHostSession host_session) {
@@ -1183,7 +1117,7 @@ namespace Frida {
 		}
 	}
 
-	private class CrashMonitor : Object {
+	private sealed class CrashMonitor : Object {
 		public signal void process_crashed (CrashInfo crash);
 
 		private Object logcat;
@@ -1613,7 +1547,7 @@ namespace Frida {
 		return result.str;
 	}
 
-	private class PackageEntrypoint : Object {
+	private abstract class PackageEntrypoint : Object {
 		public int uid {
 			get;
 			set;
@@ -1673,13 +1607,13 @@ namespace Frida {
 		}
 	}
 
-	private class DefaultActivityEntrypoint : PackageEntrypoint {
+	private sealed class DefaultActivityEntrypoint : PackageEntrypoint {
 		public DefaultActivityEntrypoint () {
 			Object ();
 		}
 	}
 
-	private class ActivityEntrypoint : PackageEntrypoint {
+	private sealed class ActivityEntrypoint : PackageEntrypoint {
 		public string activity {
 			get;
 			construct;
@@ -1690,7 +1624,7 @@ namespace Frida {
 		}
 	}
 
-	private class BroadcastReceiverEntrypoint : PackageEntrypoint {
+	private sealed class BroadcastReceiverEntrypoint : PackageEntrypoint {
 		public string receiver {
 			get;
 			construct;

src/portal-service.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class PortalService : Object {
+	public sealed class PortalService : Object {
 		public signal void node_connected (uint connection_id, SocketAddress remote_address);
 		public signal void node_joined (uint connection_id, Application application);
 		public signal void node_left (uint connection_id, Application application);
@@ -986,7 +986,7 @@ namespace Frida {
 				if (host_session != channel)
 					throw new Error.INVALID_ARGUMENT ("Invalid host session");
 
-				AgentSessionEntry entry = parent.sessions[id];
+				AgentSessionEntry? entry = parent.sessions[id];
 				if (entry == null)
 					throw new Error.INVALID_ARGUMENT ("Invalid session ID");
 
@@ -1000,6 +1000,33 @@ namespace Frida {
 				return entry.session;
 			}
 
+			public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+				if (host_session != channel)
+					return;
+
+				AgentSessionEntry? entry = parent.sessions[id];
+				if (entry == null)
+					return;
+
+				entry.clear_node_registrations ();
+			}
+
+			public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+					throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+			}
+
+			public void unlink_channel (HostSession host_session, ChannelId id) {
+			}
+
+			public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id,
+					Cancellable? cancellable) throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+			}
+
+			public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+			}
+
 			private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
 				agent_session_detached (id, reason, crash);
 			}
@@ -1278,6 +1305,14 @@ namespace Frida {
 					Cancellable? cancellable) throws Error, IOError {
 				throw new Error.NOT_SUPPORTED ("Not supported");
 			}
+
+			public async ChannelId open_channel (string address, Cancellable? cancellable) throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Channels are not supported by this backend");
+			}
+
+			public async ServiceSessionId open_service (string address, Cancellable? cancellable) throws Error, IOError {
+				throw new Error.NOT_SUPPORTED ("Services are not supported by this backend");
+			}
 		}
 
 		private class BusService : Object, BusSession {
@@ -1516,8 +1551,16 @@ namespace Frida {
 			}
 
 			private void unregister_all () {
+				clear_controller_registrations ();
+				clear_node_registrations ();
+			}
+
+			private void clear_controller_registrations () {
 				if (controller != null)
 					unregister_all_in (controller_registrations, controller.connection);
+			}
+
+			public void clear_node_registrations () {
 				if (node != null)
 					unregister_all_in (node_registrations, node.connection);
 			}

src/qnx/qinjector.vala

@@ -133,7 +133,7 @@ namespace Frida {
 		public extern void _free_instance (void * instance, UnloadPolicy unload_policy);
 		public extern uint _do_inject (uint pid, string path, string entrypoint, string data, string temp_path) throws Error;
 
-		public class ResourceStore {
+		public sealed class ResourceStore {
 			public TemporaryDirectory tempdir {
 				get;
 				private set;
@@ -164,7 +164,7 @@ namespace Frida {
 		}
 	}
 
-	public class AgentDescriptor : Object {
+	public sealed class AgentDescriptor : Object {
 		public string name {
 			get;
 			construct;
@@ -197,7 +197,7 @@ namespace Frida {
 		}
 	}
 
-	private class RemoteThreadSession : Object {
+	private sealed class RemoteThreadSession : Object {
 		public signal void ended (UnloadPolicy unload_policy);
 
 		public uint id {

src/qnx/qnx-host-session.vala

@@ -1,82 +1,17 @@
 namespace Frida {
-	public class QnxHostSessionBackend : Object, HostSessionBackend {
-		private QnxHostSessionProvider local_provider;
-
-		public async void start (Cancellable? cancellable) throws IOError {
-			assert (local_provider == null);
-			local_provider = new QnxHostSessionProvider ();
-			provider_available (local_provider);
-		}
-
-		public async void stop (Cancellable? cancellable) throws IOError {
-			assert (local_provider != null);
-			provider_unavailable (local_provider);
-			yield local_provider.close (cancellable);
-			local_provider = null;
+	public sealed class QnxHostSessionBackend : LocalHostSessionBackend {
+		protected override LocalHostSessionProvider make_provider () {
+			return new QnxHostSessionProvider ();
 		}
 	}
 
-	public class QnxHostSessionProvider : Object, HostSessionProvider {
-		public string id {
-			get { return "local"; }
-		}
-
-		public string name {
-			get { return "Local System"; }
-		}
-
-		public Variant? icon {
-			get { return null; }
-		}
-
-		public HostSessionProviderKind kind {
-			get { return HostSessionProviderKind.LOCAL; }
-		}
-
-		private QnxHostSession host_session;
-
-		public async void close (Cancellable? cancellable) throws IOError {
-			if (host_session == null)
-				return;
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async HostSession create (HostSessionOptions? options, Cancellable? cancellable) throws Error, IOError {
-			if (host_session != null)
-				throw new Error.INVALID_OPERATION ("Already created");
-
-			host_session = new QnxHostSession ();
-			host_session.agent_session_detached.connect (on_agent_session_detached);
-
-			return host_session;
-		}
-
-		public async void destroy (HostSession session, Cancellable? cancellable) throws Error, IOError {
-			if (session != host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			host_session.agent_session_detached.disconnect (on_agent_session_detached);
-
-			yield host_session.close (cancellable);
-			host_session = null;
-		}
-
-		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
-				Cancellable? cancellable) throws Error, IOError {
-			if (host_session != this.host_session)
-				throw new Error.INVALID_ARGUMENT ("Invalid host session");
-
-			return yield this.host_session.link_agent_session (id, sink, cancellable);
-		}
-
-		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
-			agent_session_detached (id, reason, crash);
+	public sealed class QnxHostSessionProvider : LocalHostSessionProvider {
+		protected override LocalHostSession make_host_session (HostSessionOptions? options) throws Error {
+			return new QnxHostSession ();
 		}
 	}
 
-	public class QnxHostSession : BaseDBusHostSession {
+	public sealed class QnxHostSession : LocalHostSession {
 		private AgentContainer system_session_container;
 
 		private AgentDescriptor agent_desc;

src/socket/socket-host-session.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class SocketHostSessionBackend : Object, HostSessionBackend {
+	public sealed class SocketHostSessionBackend : Object, HostSessionBackend {
 		private SocketHostSessionProvider provider;
 
 		public async void start (Cancellable? cancellable) throws IOError {
@@ -14,7 +14,7 @@ namespace Frida {
 		}
 	}
 
-	public class SocketHostSessionProvider : Object, HostSessionProvider {
+	public sealed class SocketHostSessionProvider : Object, HostSessionProvider {
 		public string id {
 			get { return "socket"; }
 		}
@@ -199,6 +199,21 @@ namespace Frida {
 			host_session_detached (entry.host_session);
 		}
 
+		private HostEntry get_host_entry_by_session (HostSession session) throws Error {
+			var entry = find_host_entry_by_session (session);
+			if (entry == null)
+				throw new Error.INVALID_ARGUMENT ("Invalid host session");
+			return entry;
+		}
+
+		private HostEntry? find_host_entry_by_session (HostSession session) {
+			foreach (var entry in hosts) {
+				if (entry.host_session == session)
+					return entry;
+			}
+			return null;
+		}
+
 		private void on_host_connection_closed (DBusConnection connection, bool remote_peer_vanished, GLib.Error? error) {
 			bool closed_by_us = (!remote_peer_vanished && error == null);
 			if (closed_by_us)
@@ -219,11 +234,38 @@ namespace Frida {
 
 		public async AgentSession link_agent_session (HostSession host_session, AgentSessionId id, AgentMessageSink sink,
 				Cancellable? cancellable) throws Error, IOError {
-			foreach (var entry in hosts) {
-				if (entry.host_session == host_session)
-					return yield entry.link_agent_session (id, sink, cancellable);
-			}
-			throw new Error.INVALID_ARGUMENT ("Invalid host session");
+			var entry = get_host_entry_by_session (host_session);
+			return yield entry.link_agent_session (id, sink, cancellable);
+		}
+
+		public void unlink_agent_session (HostSession host_session, AgentSessionId id) {
+			var entry = find_host_entry_by_session (host_session);
+			if (entry != null)
+				entry.unlink_agent_session (id);
+		}
+
+		public async IOStream link_channel (HostSession host_session, ChannelId id, Cancellable? cancellable)
+				throws Error, IOError {
+			var entry = get_host_entry_by_session (host_session);
+			return yield entry.link_channel (id, cancellable);
+		}
+
+		public void unlink_channel (HostSession host_session, ChannelId id) {
+			var entry = find_host_entry_by_session (host_session);
+			if (entry != null)
+				entry.unlink_channel (id);
+		}
+
+		public async ServiceSession link_service_session (HostSession host_session, ServiceSessionId id, Cancellable? cancellable)
+				throws Error, IOError {
+			var entry = get_host_entry_by_session (host_session);
+			return yield entry.link_service_session (id, cancellable);
+		}
+
+		public void unlink_service_session (HostSession host_session, ServiceSessionId id) {
+			var entry = find_host_entry_by_session (host_session);
+			if (entry != null)
+				entry.unlink_service_session (id);
 		}
 
 		private void on_agent_session_detached (AgentSessionId id, SessionDetachReason reason, CrashInfo crash) {
@@ -252,6 +294,8 @@ namespace Frida {
 
 			private Gee.HashMap<AgentSessionId?, AgentSessionEntry> agent_sessions =
 				new Gee.HashMap<AgentSessionId?, AgentSessionEntry> (AgentSessionId.hash, AgentSessionId.equal);
+			private ChannelRegistry channel_registry = new ChannelRegistry ();
+			private ServiceSessionRegistry service_session_registry = new ServiceSessionRegistry ();
 
 			private Cancellable io_cancellable = new Cancellable ();
 
@@ -291,6 +335,10 @@ namespace Frida {
 					agent_session_detached (id, reason, no_crash);
 				agent_sessions.clear ();
 
+				channel_registry.clear ();
+
+				service_session_registry.clear ();
+
 				if (reason != CONNECTION_TERMINATED) {
 					try {
 						yield connection.close (cancellable);
@@ -315,6 +363,41 @@ namespace Frida {
 				return session;
 			}
 
+			public void unlink_agent_session (AgentSessionId id) {
+				AgentSessionEntry? entry = agent_sessions[id];
+				if (entry == null || entry.sink_registration_id == 0)
+					return;
+
+				entry.connection.unregister_object (entry.sink_registration_id);
+				entry.sink_registration_id = 0;
+			}
+
+			public async IOStream link_channel (ChannelId id, Cancellable? cancellable) throws Error, IOError {
+				Channel channel = yield connection.get_proxy (null, ObjectPath.for_channel (id),
+					DO_NOT_LOAD_PROPERTIES, cancellable);
+
+				var stream = new ChannelStream (channel);
+				channel_registry.register (id, stream);
+
+				return stream;
+			}
+
+			public void unlink_channel (ChannelId id) {
+				channel_registry.unlink (id);
+			}
+
+			public async ServiceSession link_service_session (ServiceSessionId id, Cancellable? cancellable)
+					throws Error, IOError {
+				ServiceSession session = yield connection.get_proxy (null, ObjectPath.for_service_session (id),
+					DO_NOT_LOAD_PROPERTIES, cancellable);
+				service_session_registry.register (id, session);
+				return session;
+			}
+
+			public void unlink_service_session (ServiceSessionId id) {
+				service_session_registry.unlink (id);
+			}
+
 			private bool on_keepalive_tick () {
 				host_session.ping.begin (keepalive_interval, io_cancellable);
 				return true;

src/system.vala

@@ -6,7 +6,7 @@ namespace Frida {
 		public extern static void kill (uint pid);
 	}
 
-	public class ApplicationEnumerator : Object {
+	public sealed class ApplicationEnumerator : Object {
 		private ThreadPool<EnumerateRequest> pool;
 		private MainContext main_context;
 
@@ -68,7 +68,7 @@ namespace Frida {
 		}
 	}
 
-	public class ProcessEnumerator : Object {
+	public sealed class ProcessEnumerator : Object {
 		private ThreadPool<EnumerateRequest> pool;
 		private MainContext main_context;
 
@@ -130,7 +130,7 @@ namespace Frida {
 		}
 	}
 
-	public class TemporaryDirectory {
+	public sealed class TemporaryDirectory {
 		private string? name;
 
 		public string path {
@@ -247,7 +247,7 @@ namespace Frida {
 		private extern static string get_system_tmp ();
 	}
 
-	public class TemporaryFile {
+	public sealed class TemporaryFile {
 		public string path {
 			owned get {
 				return file.get_path ();

src/windows/frida-helper-backend.vala

@@ -1,5 +1,5 @@
 namespace Frida {
-	public class WindowsHelperBackend : Object, WindowsHelper {
+	public sealed class WindowsHelperBackend : Object, WindowsHelper {
 		public PrivilegeLevel level {
 			get;
 			construct;
@@ -127,7 +127,7 @@ namespace Frida {
 		}
 	}
 
-	private class AssetDirectory {
+	private sealed class AssetDirectory {
 		public File file {
 			get;
 			private set;
@@ -170,7 +170,7 @@ namespace Frida {
 		}
 	}
 
-	private class AssetBundle {
+	private sealed class AssetBundle {
 		public Gee.List<File> files {
 			get;
 			private set;