无法从发出的事件接收有效载荷 - Socket.io

Question

I have a socket with authentification server which looks like this:

const io = require('socket.io').listen(3002);
const jwt = require('jsonwebtoken');

io.use((socket, next) => {
  if (socket.handshake.query && socket.handshake.query.token) {
    jwt.verify(
      socket.handshake.query.token,
      '4-8-15-16-23-42',
      (err, decoded) => {
        if (err) return next(new Error('Authentication error'));
        socket.decoded = decoded;
        next();
      }
    );
  } else {
    next(new Error('Authentication error'));
  }
}).on('connection', socket => {
  socket.emit('connect', 'socket server is connected'); //sending message

  socket.on('recieved', socket => {
    console.log(socket);
  });
});

And the client side looks like this:

  ...
  useEffect(() => {
    const token = sessionStorage.getItem('token');
    const socket = io('http://localhost:3002', {
      query: { token }
    });

    socket.on('connect', msg => {
      console.log(msg); //undefined
    });
  }, []);
  ...

The problem is that the connection is done but after that when I want to emit another event from my server with some payload, I can't receive the payload on the other side by listening to it.

Answer 1

the problem is that the event "connect" you emit is an already "reserved" event that is send from socket server when a socket is successfully connected.

Just do the following change

Rename the event ex from "connect" to "connected" in both side (client and server) "Server" code

 socket.emit('connected', 'socket server is connected');

and on the "Client"

socket.on('connected', msg => {
  console.log(msg); //msg will no longer be "undefined"
});

and you will be ok