horizon-mods/native/voicechat-server

Voice chat server (Horizon native mod)

The server half of proximity voice chat on a Horizon dedicated server. Players who have a voice chat client mod (azetech's Complex Voice Chat, any client that speaks Simple Voice Chat 2.6.x's protocol over Horizon's mod messages) talk to the players near them, or to their group from anywhere. Players without one join and play as on any server: the server sends them nothing.

• The handshake goes over Horizon's mod messages (native_net_from_client / native_net_send_to_player, the horizon:mod_net channel) on voicechat: channel names, the same messages and layouts as Simple Voice Chat 2.6.x (compatibility version 20). A client gets a fresh 16-byte secret when it asks; nothing is sent to anyone before.
• Voices go over UDP, through the server, never from player to player: no player learns another's address. Each player's packets are sealed with their own secret (AES-128-GCM). The server relays a voice to the players in the same dimension within distance blocks (whisper_distance for a whisper), and to the speaker's group wherever they are. Groups: normal (members aren't heard outside but hear who is near), open (heard and hearing nearby), isolated (members only).
• Limits: 75 voice packets a second a player (burst 30), Opus frames up to 1275 bytes, 128 groups, names and passwords up to 24 characters, group and state changes 2 a second a player (burst 10), one secret a second a player (more requests meanwhile get one answer), 24 messages a player a tick and at most 512 waiting.
• Replays: a packet that doesn't open with the player's key is dropped without an answer. A secret belongs to the first address that authenticates with it: a handshake copied and sent from elsewhere moves nothing. Exact copies are dropped too (the last 64 control packets' nonces, and voice packets' sequence numbers). A client the server stops hearing for 10 keep-alives (its NAT rebound, say) gets a fresh secret over the game connection and comes back from its new address with it; the old key then opens nothing.
• No port is opened until the first voice chat client asks. Then the relay binds bind:port (UDP).

Config

config/voicechat-server.json, beside server.properties, written with its defaults the first time a client asks:

Key	Default
enabled	true	false: no port, no answer to clients
port	24454	the UDP port. A host that gives one port for the game usually forwards UDP on it too: use the game's port
bind	0.0.0.0
voice_host	""	where clients send UDP if not the game server's address: a port, a host, or host:port
distance	48.0	blocks a voice carries
whisper_distance	24.0
groups	true	players may make and join groups
keep_alive_ms	1000	a client silent 10 times this long shows as disconnected
mtu	1024

Files

File	What it is
mixins/voicechat_server/horizon-mixin.toml	The bundle: the relay crate, the glue module and four HEAD hooks (mod messages, server tick, player logged out, world closing)
mixins/voicechat_server/relay/	The relay crate (voicechat_server_relay): the wire format (proto.rs), the handshake, groups and UDP relay (lib.rs) and its tests over real UDP sockets (tests.rs). Depends on ring (AES-GCM) and serde, both in Horizon's Cargo.lock
mixins/voicechat_server/glue.rs	Added to the game as game::voicechat_server: the config, starting the relay, the players each tick

It needs horizon-mixins 0.6.0 (bundle crates) and hook points API 57. Tests: cargo test here.

Not made with or endorsed by Simple Voice Chat or its author: it speaks the same protocol, written from its packet layouts, with none of its code.