``fetchSockets()`` always returns ``RemoteSocket[]``

[nathan6am]

Describe the bug
I am trying to retrieve a socket instance by its id, however, using the io.fetchSockets() method always returns a RemoteSocket[], so methods like socket.timeout can't be used from the resulting instance. According to the docs fetchSockets should return Socket[] | RemoteSocket[]. I am not using an adapter and the behavior is the same in main namespace.

To Reproduce

Please fill the following code example:

Socket.IO server version: 4.5.4

Server

//Returns a Promise<RemoteSocket | undefined>
const socketInstanceById = async (socketId: string) => {
    const sockets = await io.in(socketId).fetchSockets(); 
    for (const socket of sockets) {
      if (socket.id === socketId) return socket;
    }
 }

Reducing the example to

const sockets = await io.fetchSockets()
//Type of `sockets` is RemoteSocket[]

Is fetchSockets the only way to retrieve a socket instance by its id? If so is there a way to get a Socket instance and not a RemoteSocket?

Expected behavior
fetchSockets should return normal socket instances when called on the same server.

[darrachequesne]

Getting a RemoteSocket means the client is connected on another server of the cluster.

Regarding the timeout() method, it's a known issue that should be fixed soon: #4558

[nathan6am]

Why would I get a RemoteSocket if I am only using a single server with no clustering? As far as I can tell, fetchSockets() will always return RemoteSocket[] regardless of whether or not the client is connected to another server on the cluster, including without using clustering at all, while according to the docs it should return either Socket[] | RemoteSocket[]

socket.io/lib/broadcast-operator.ts

Lines 318 to 338 in 54d5ee0

	public fetchSockets(): Promise<RemoteSocket<EmitEvents, SocketData>[]> {
	return this.adapter
	.fetchSockets({
	rooms: this.rooms,
	except: this.exceptRooms,
	flags: this.flags,
	})
	.then((sockets) => {
	return sockets.map((socket) => {
	if (socket instanceof Socket) {
	// FIXME the TypeScript compiler complains about missing private properties
	return socket as unknown as RemoteSocket<EmitEvents, SocketData>;
	} else {
	return new RemoteSocket(
	this.adapter,
	socket as SocketDetails<SocketData>
	);
	}
	});
	});
	}

[darrachequesne]

The type of the fetchSockets() response is RemoteSocket[], but it might actually contain some Socket instances (for sockets that are on the given server), which share more or less the same interface:

socket.io/lib/broadcast-operator.ts

Lines 327 to 329 in 54d5ee0

	if (socket instanceof Socket) {
	// FIXME the TypeScript compiler complains about missing private properties
	return socket as unknown as RemoteSocket<EmitEvents, SocketData>;

Is there anything that should be exposed by the RemoteSocket interface?

[darrachequesne]

For future readers:

remoteSocket.timeout() was added in 0c0eb00, included in version 4.6.0.

Please reopen if needed!

[TonyLst]

Getting a RemoteSocket means the client is connected on another server of the cluster.

Regarding the timeout() method, it's a known issue that should be fixed soon: #4558

Is there a way to get complete Socket client instance instead of RemoteSocket when using fetchSockets() in clusterized app?

I would like to access socket.request.user property (user prop is provided by my express-session/passportjs middlewares) juste as i was able to access when my app was not clusterized:

const activeParticipants: Array<Participant> = (
            await browserSocket.adapter.fetchSockets({
                rooms: new Set([code]),
            })
        )
            .map(
                (socket) =>
                    (socket as unknown as BrowserSocket).request.user
            )
            .filter((user) => !isUserAdmin(user));

RemoteClient actually not includes socket.request 😭

[darrachequesne]

Hi! The request object is a Node.js IncomingMessage message, and cannot be serialized.

You can include the user's id in the socket.data attribute:

io.on("connection", (socket) => {
  socket.data.userId = socket.request.user.id;
});

And then use it with fetchSockets():

const sockets = await io.fetchSockets();

for (const socket of sockets) {
  console.log(socket.data.userId);
}