Implement WebSocket Connections

# WebSocket Real-time Chat Implementation ## Server Code (Node.js + Socket.IO) ```javascript const express = require('express'); const http = require('http'); const socketIo = require('socket.io'); const jwt = require('jsonwebtoken'); const rateLimit = require('express-rate-limit'); const app = express(); const server = http.createServer(app); const io = socketIo(server, { cors: { origin: '*' }, maxHttpBufferSize: 1e6 }); // Rate limiting const limiter = rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 100 // limit each IP to 100 requests per windowMs }); // Authentication middleware io.use((socket, next) => { const token = socket.handshake.auth.token; try { const decoded = jwt.verify(token, process.env.JWT_SECRET); socket.userId = decoded.userId; next(); } catch (err) { next(new Error('Authentication error')); } }); const activeConnections = new Map(); io.on('connection', (socket) => { console.log(`User ${socket.userId} connected`); activeConnections.set(socket.userId, socket.id); // Handle different message types socket.on('text_message', (data) => { const message = { id: Date.now(), userId: socket.userId, content: data.content, timestamp: new Date(), type: 'text' }; // Broadcast to all clients in room socket.to(data.roomId).emit('new_message', message); }); socket.on('join_room', (roomId) => { socket.join(roomId); socket.emit('room_joined', { roomId, status: 'success' }); }); socket.on('disconnect', () => { console.log(`User ${socket.userId} disconnected`); activeConnections.delete(socket.userId); }); // Heartbeat socket.on('ping', () => { socket.emit('pong'); }); }); server.listen(3000, () => { console.log('WebSocket server running on port 3000'); }); ``` ## Client Code (JavaScript/React) ```javascript import { io } from 'socket.io-client'; class WebSocketClient { constructor(token) { this.token = token; this.socket = null; this.reconnectAttempts = 0; this.maxReconnectAttempts = 5; this.messageQueue = []; } connect() { this.socket = io('ws://localhost:3000', { auth: { token: this.token }, autoConnect: false }); this.socket.on('connect', () => { console.log('Connected to server'); this.reconnectAttempts = 0; this.flushMessageQueue(); }); this.socket.on('disconnect', () => { console.log('Disconnected from server'); this.handleReconnect(); }); this.socket.on('connect_error', (error) => { console.error('Connection error:', error.message); }); this.socket.connect(); } handleReconnect() { if (this.reconnectAttempts < this.maxReconnectAttempts) { const delay = Math.pow(2, this.reconnectAttempts) * 1000; setTimeout(() => { this.reconnectAttempts++; this.socket.connect(); }, delay); } } sendMessage(roomId, content) { const message = { roomId, content, timestamp: Date.now() }; if (this.socket.connected) { this.socket.emit('text_message', message); } else { this.messageQueue.push(message); } } flushMessageQueue() { while (this.messageQueue.length > 0) { const message = this.messageQueue.shift(); this.socket.emit('text_message', message); } } } // Usage const client = new WebSocketClient('your-jwt-token'); client.connect(); ```