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WebSocket Server

Why we will use socket.io​

If you want to configure CORS for your Socket.io server without using additional packages like cors, you can directly configure it within the socketio initialization options.

const express = require('express');
const http = require('http');
const { Server } = require('socket.io');

const app = express();
const server = http.createServer(app);

// Configure Socket.io with CORS
const io = new Server(server, {
    cors: {
        origin: "https://localhost:3000", // Allow from specific origin
        methods: ["GET", "POST"] // Allow only GET and POST methods
    }
});

// Socket.io connection handling
io.on('connection', (socket) => {
    console.log('A user connected');

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

    // Example: Handle incoming messages
    socket.on('chat message', (msg) => {
        console.log('Message received: ' + msg);
        io.emit('chat message', msg); // Broadcast message to all connected clients
    });
});

// Start server
const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
    console.log(`Server running on port ${PORT}`);
});

Explanation:​

  1. Socket.io Server Initialization:

    • Instead of importing socket.io, we're using { Server } from socket.io. This allows us to directly configure the server options when creating the instance.

  2. CORS Configuration:

    • The cors option within Server constructor allows specifying CORS settings.
    • origin: Specifies the allowed origin. In this example, it allows requests from https://localhost:3000.
    • methods: Specifies the allowed HTTP methods. Here, only GET and POST methods are allowed.

  3. Socket.io Connection Handling:

    • Handles socket connections (io.on('connection', ...)) and disconnections (socket.on('disconnect', ...)).
    • Includes an example of handling incoming messages (socket.on('chat message', ...)), echoing them back to all clients (io.emit('chat message', ...)).

  4. Server Startup:

    • Starts the HTTP server (server.listen(...)), specifying the port number (PORT) to listen on.

This setup allows you to control CORS directly within the Socket.io server configuration, without needing additional middleware like cors. Adjust the origin and methods as per your specific requirements. Remember to handle client-side connections and events accordingly in your frontend application.

Documentation​