Unable to connect to socket.io using express server

Question

I'm trying to create WebSocket using the following code.

const express = require('express')
const app = express()
const http = require('http')
const server = new http.createServer(app)
const io = require('socket.io')(server)

const CONFIG = {
    host: 'localhost',
    port: 4444
}

io.on('connection', function (socket) {
    const sid = socket.id

    console.log('connection socket id:', sid)

    for (const msg of ['disconnect', 'disconnecting', 'error']) {
        socket.on(msg, data => {
            console.log(`* ${msg}:`, data)
        })
    }

    socket.on('join', data => {
        console.console.log("data", data)
    })

    socket.on('signal', data => {
        console.log('signal', data)
    })
})

server.listen({
    host: CONFIG.host,
    port: CONFIG.port,
}, info => {
    console.info(`Running on`, server.address())
})

When I try to test this using https://www.websocket.org/echo.html I'm receiving an undefined error.

I have given ws://127.0.0.1:4444 in the location field but when I try to connect I'm getting the following error in the Log:

ERROR: undefined

and in the message Connection closed before receiving a handshake response

What is wrong here how I can make this working?

user_1371995 · Answer

Your server seems good, you should implement the client yourself.

Socket.IO server and client example from the documentation.

Server:

var app = require('express')();
var http = require('http').createServer(app);
var io = require('socket.io')(http);

app.get('/', (req, res) => {
  res.sendFile(__dirname + '/index.html');
});

io.on('connection', (socket) => {
  socket.on('message', (msg) => {
    console.log('message: ' + msg);
  });
});

http.listen(3000, () => {
  console.log('listening on *:3000');
});

Client (index.html):

Unable to connect to socket.io using express server

1 Answers