Server: the game thread is the keep-alive timeout's only judge; kick, then close a second later

The writer thread's own check raced it and logged "Disconnected" instead of
vanilla's "Timed out".

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/horizon-client/src/lan/conn.rs

@@ -1337,22 +1337,16 @@ fn write_loop(
             Err(RecvTimeoutError::Timeout) => {}
         }
         let now = Instant::now();
-        if let Some((id, at)) = sent_at {
-            if alive.load(Ordering::Relaxed) == id {
-                let ms = i32::try_from(at.elapsed().as_millis()).unwrap_or(i32::MAX);
-                let old = latency.load(Ordering::Relaxed);
-                latency.store((old * 3 + ms) / 4, Ordering::Relaxed);
-                sent_at = None;
-            } else if at.elapsed() >= KEEP_ALIVE_EVERY {
-                let _ = writer.send(
-                    &play::Clientbound::Disconnect(cfg::Disconnect {
-                        reason: translatable("disconnect.timeout", &[]),
-                    })
-                    .encode(),
-                );
-                break;
-            }
+        if let Some((id, at)) = sent_at
+            && alive.load(Ordering::Relaxed) == id
+        {
+            let ms = i32::try_from(at.elapsed().as_millis()).unwrap_or(i32::MAX);
+            let old = latency.load(Ordering::Relaxed);
+            latency.store((old * 3 + ms) / 4, Ordering::Relaxed);
+            sent_at = None;
         }
+        // The game thread times a client out ([`PlayerSender::timed_out`]):
+        // this thread may be blocked on a client that stopped reading.
         if sent_at.is_none() && now >= next {
             let id = i64::try_from(start.elapsed().as_millis()).unwrap_or(0);
             if writer

crates/horizon-client/src/lan/hub.rs

@@ -1192,10 +1192,16 @@ impl Hub {
                 }
             }
         }
-        // keepConnectionAlive's timeout, checked once a second here as well:
-        // a client that stops reading blocks its writer thread, which sends
-        // the keep-alives and checks them, and would hold its slot forever.
+        // keepConnectionAlive's timeout, checked once a second here, not on
+        // the writer thread: a client that stops reading blocks that thread
+        // and would hold its slot forever. Kicked, it gets the reason; still
+        // here a second later, its connection is closed under the writer.
         if self.ticks.is_multiple_of(20) {
+            for g in &self.guests {
+                if !g.left_reason.is_empty() && g.sender.timed_out() {
+                    g.sender.close();
+                }
+            }
             let silent: Vec<u32> = self
                 .guests
                 .iter()
@@ -1204,9 +1210,6 @@ impl Hub {
                 .collect();
             for conn in silent {
                 self.kick(conn, translatable("disconnect.timeout", &[]));
-                if let Some(g) = self.guest(conn) {
-                    g.sender.close();
-                }
             }
         }
         events