Server: Latency & Liveness

Mesh uses an application-level ping/pong system to track connection health, measure latency, and ensure stale connections are cleaned up across instances.

This works independently of WebSocket protocol-level ping frames and gives you:

• Accurate round-trip latency tracking
• Configurable liveness timeouts
• Automatic cleanup of dead connections and their state (rooms, presence, etc.)

Configuration

You can configure ping/liveness behavior via the server constructor:

const server = new MeshServer({
  redisOptions: { host: "localhost", port: 6379 },
  pingInterval: 30_000, // how often to ping clients
  latencyInterval: 5_000, // how often to request latency from clients
  maxMissedPongs: 1, // allowed missed pongs before disconnecting
});

What happens under the hood

Every connection:

1. Sends a "ping" command every pingInterval

   • If no "pong" is received, it’s marked as inactive
   • If missedPongs > maxMissedPongs, the connection is closed

2. Sends a "latency:request" every latencyInterval

   • When the client responds with "latency:response", Mesh calculates round-trip time and can emit latency stats

3. On receiving "pong", the connection is marked as alive and its presence TTL is refreshed

Presence TTL is only refreshed when a valid "pong" is received, meaning that missed pongs will eventually cause Redis to expire presence entries and trigger a "leave" event.

Why Mesh doesn’t use native WebSocket pings

• Native pings don’t go through your app layer, so you can’t measure latency
• Native pings don’t support multi-instance cleanup
• Native pings can’t update Redis TTLs for presence tracking

Mesh solves all of that with application-level control.

Monitoring latency (optional)

Mesh automatically tracks round-trip latency.

If you want to observe it on the client:

client.on("latency", (ms) => {
  console.log("Latency:", ms, "ms");
});

This is useful for:

• Displaying latency to users (e.g. in a status bar)
• Logging latency over time for diagnostics
• Detecting network slowdowns

See Client SDK → Latency & Reconnect for configuration on the client side.