Emit to room not work with uWebsocketjs

[SaltFish001]

Describe the bug
Emit some message to room not work with uWebsocketjs, but clients does`t got any message.
To Reproduce

Please fill the following code example:

Socket.IO server version: x.y.z

Server

import { Server as socket_server } from 'socket.io';
import { App } from 'uWebSockets.js';

const uapp = App();
const socket_instance = new socket_server({
  path: '/socket',
});
socket_instance.attachApp(uapp);
socket_instance.use((scoket, next) => {
  console.log('socket connect >>>', scoket.id);
  scoket.join('test');
  setTimeout(() => {
    console.log('socket emit >>>', scoket.rooms);
    socket_instance.to('test').emit('message', 'hello world');
  }, 2000);
  return next();
});

uapp.listen(9999, (token) => {
  console.log(token);
  console.log('server is listening on port 8888');
});

Socket.IO client version: x.y.z

Client

import { io } from 'socket.io-client';
const client = io('http://localhost:9999', {
  path: '/socket',
  transports: ['websocket'],
});

client.onAny((...arg) => {
  console.log('onany >>>', arg);
});
client.connect();

Expected behavior
A clear and concise description of what you expected to happen.

Platform:

• Device: [e.g. Samsung S8]
• OS: [e.g. Android 9.2]

Additional context
Socket.io & Socket.io-client 4.7.5
uWebsocketjs 20.44.0

[darrachequesne]

Hi! I was indeed able to reproduce the issue.

It does not seem to happen with uWebSockets.js#v20.30.0 though, this needs some additional investigation.

[SaltFish001]

Hi! I was indeed able to reproduce the issue.嗨！我确实能够重现这个问题。

It does not seem to happen with uWebSockets.js#v20.30.0 though, this needs some additional investigation.然而，这种情况在 身上似乎并未出现，这需要进一步的调查。

Thanks reply. Right now I can use fetchSockets get all socket , then foreach sockets to emit event. Hope this is not a hard work for you.

[TXWSLYF]

I think I found the cause of this bug.This is because during the execution of the middleware, the socket has not yet been added to the adapter's namespace.

const { Server: socket_server } = require("socket.io");
const { App } = require("uWebSockets.js");

const uapp = App();
const socket_instance = new socket_server({
  path: "/socket",
});
socket_instance.attachApp(uapp);
socket_instance.use((scoket, next) => {
  console.log("socket connect >>>", scoket.id);

  // console.log adapter's namespace
  console.log(scoket.adapter.nsp.sockets, '----');
  scoket.join("test");

  setTimeout(() => {
    console.log("socket emit >>>", scoket.rooms);
    socket_instance.to("test").emit("message", "hello world");
  }, 2000);
  return next();
});

uapp.listen(9999, (token) => {
  console.log(token);
  console.log("server is listening on port 9999");
});

---

when call the scoket.join("test"), it's actually call:

socket.io/packages/socket.io/lib/socket.ts

Lines 554 to 561 in 582655f

	public join(rooms: Room | Array<Room>): Promise<void> | void {
	debug("join room %s", rooms);
	return this.adapter.addAll(
	this.id,
	new Set(Array.isArray(rooms) ? rooms : [rooms])
	);
	}

when the socket_instance.attachApp is called, the Adapter.prototype.addAll would be rewrite:

socket.io/packages/socket.io/lib/uws.ts

Lines 14 to 33 in 582655f

	Adapter.prototype.addAll = function (id, rooms) {
	const isNew = !this.sids.has(id);
	addAll.call(this, id, rooms);
	const socket: Socket = this.nsp.sockets.get(id);
	if (!socket) {
	return;
	}
	if (socket.conn.transport.name === "websocket") {
	subscribe(this.nsp.name, socket, isNew, rooms);
	return;
	}
	if (isNew) {
	socket.conn.on("upgrade", () => {
	const rooms = this.sids.get(id);
	if (rooms) {
	subscribe(this.nsp.name, socket, isNew, rooms);
	}
	});
	}
	};

this bug happend here, we can't find the socket in the nsp now, so it's just return and didn't call the subscribe fun.

const socket: Socket = this.nsp.sockets.get(id); 
 if (!socket) { 
   return; 
 } 

and why we can't get the socket by id from the nsp here is due to the execution order of the middleware and _doConnect method.

socket.io/packages/socket.io/lib/namespace.ts

Lines 334 to 357 in 582655f

	this.run(socket, (err) => {
	process.nextTick(() => {
	if ("open" !== client.conn.readyState) {
	debug("next called after client was closed - ignoring socket");
	socket._cleanup();
	return;
	}
	if (err) {
	debug("middleware error, sending CONNECT_ERROR packet to the client");
	socket._cleanup();
	if (client.conn.protocol === 3) {
	return socket._error(err.data || err.message);
	} else {
	return socket._error({
	message: err.message,
	data: err.data,
	});
	}
	}
	this._doConnect(socket, fn);
	});
	});

The _doConnect method will only be executed when all the middleware has been executed, which track the socket.

[TXWSLYF]

for the example below, we don't use uWebsocketjs this time, even if the socket has not yet been added to the adapter's namespace, it also works well.

const { Server: socket_server } = require("socket.io");

const socket_instance = new socket_server({
  path: "/socket",
});
socket_instance.use((scoket, next) => {
  console.log("socket connect >>>", scoket.id);
  console.log(scoket.adapter.nsp.sockets, '----');
  scoket.join("test");

  setTimeout(() => {
    console.log("socket emit >>>", scoket.rooms);
    socket_instance.to("test").emit("message", "hello world");
  }, 2000);
  return next();
});

socket_instance.listen(9999, (token) => {
  console.log(token);
  console.log("server is listening on port 9999");
});

this is because by default, the join method use the in-memory-adapter,it don't check if the socket exists now but just store the relation.

socket.io/packages/socket.io-adapter/lib/in-memory-adapter.ts

Lines 87 to 104 in 582655f

	public addAll(id: SocketId, rooms: Set<Room>): Promise<void> | void {
	if (!this.sids.has(id)) {
	this.sids.set(id, new Set());
	}
	for (const room of rooms) {
	this.sids.get(id).add(room);
	if (!this.rooms.has(room)) {
	this.rooms.set(room, new Set());
	this.emit("create-room", room);
	}
	if (!this.rooms.get(room).has(id)) {
	this.rooms.get(room).add(id);
	this.emit("join-room", room, id);
	}
	}
	}

and get the socket when emit message.

socket.io/packages/socket.io-adapter/lib/in-memory-adapter.ts

Lines 333 to 358 in 582655f

	private apply(opts: BroadcastOptions, callback: (socket) => void): void {
	const rooms = opts.rooms;
	const except = this.computeExceptSids(opts.except);
	if (rooms.size) {
	const ids = new Set();
	for (const room of rooms) {
	if (!this.rooms.has(room)) continue;
	for (const id of this.rooms.get(room)) {
	if (ids.has(id) || except.has(id)) continue;
	const socket = this.nsp.sockets.get(id);
	if (socket) {
	callback(socket);
	ids.add(id);
	}
	}
	}
	} else {
	for (const [id] of this.sids) {
	if (except.has(id)) continue;
	const socket = this.nsp.sockets.get(id);
	if (socket) callback(socket);
	}
	}
	}

[TXWSLYF]

I created a fix but don't know if it will have any other impacts, would appreciate if you could check it.

[darrachequesne]

@TXWSLYF thanks for the analysis 👍 There is indeed something wrong when calling socket.join() in a middleware.

io.use((socket, next) => {
  socket.join("test");
  next();
});

io.on("connection", (socket) => {
  io.to("test").emit("hello"); // should work
});

That being said, I'm not sure the following should work, since the socket is not connected yet:

io.use((socket, next) => {
  socket.join("test");
  io.to("test").emit("hello"); // should it really include the socket?
  next();
});

I'm looking into this.

[gkourpa]

I had the same issue here, but after upgrading to version 4.8.0 it seems to have been fixed

[darrachequesne]

For future readers:

This should be fixed by b04fa64, included in socket.io@4.8.0.