Socket.IO and Express server listening on the same port

On Scalingo, your application must listen to the port defined in the PORT environment variable dynamically defined by the platform.

If your application uses both a HTTP server and a WebSocket, you can configure it to use the same port. A complete sample is deployed here with the code being publicly available in this GitHub repository. Here is a snippet to do that with an Express server and Socket.IO for the WebSocket part:

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

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

http.listen(process.env.PORT || 3000, function() {
  var host = http.address().address
  var port = http.address().port
  console.log('App listening at https://%s:%s', host, port)
});

io.on('connection', function(socket) {
  console.log('Client connected to the WebSocket');

  socket.on('disconnect', () => {
    console.log('Client disconnected');
  });

  socket.on('chat message', function(msg) {
    console.log("Received a chat message");
    io.emit('chat message', msg);
  });
})

Last update: 22 Dec 2023 Suggest edits