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.

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.

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:

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

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.

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

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.

and get the socket when emit message.

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