Implements real-time WebSocket communication with connection management, room-based messaging, and horizontal scaling. Use when building chat systems, live notifications, collaborative tools, or real-time dashboards.
Build scalable real-time communication systems with proper connection management.
const { Server } = require('socket.io');
const { createAdapter } = require('@socket.io/redis-adapter');
const { createClient } = require('redis');
const io = new Server(server, {
cors: { origin: process.env.CLIENT_URL, credentials: true }
});
// Redis adapter for horizontal scaling
const pubClient = createClient({ url: process.env.REDIS_URL });
const subClient = pubClient.duplicate();
Promise.all([pubClient.connect(), subClient.connect()]).then(() => {
io.adapter(createAdapter(pubClient, subClient));
});
// Connection management
const users = new Map();
io.use((socket, next) => {
const token = socket.handshake.auth.token;
try {
socket.user = verifyToken(token);
next();
} catch (err) {
next(new Error('Authentication failed'));
}
});
io.on('connection', (socket) => {
users.set(socket.user.id, socket.id);
console.log(`User ${socket.user.id} connected`);
socket.on('join-room', (roomId) => {
socket.join(roomId);
socket.to(roomId).emit('user-joined', socket.user);
});
socket.on('message', ({ roomId, content }) => {
io.to(roomId).emit('message', {
userId: socket.user.id,
content,
timestamp: Date.now()
});
});
socket.on('disconnect', () => {
users.delete(socket.user.id);
});
});
// Utility methods for message distribution
function broadcastUserUpdate(userId, data) {
io.to(`user:${userId}`).emit('user-update', data);
}
function notifyRoom(roomId, event, data) {
io.to(`room:${roomId}`).emit(event, data);
}
function sendDirectMessage(userId, message) {
const socketId = users.get(userId);
if (socketId) {
io.to(socketId).emit('direct-message', message);
}
}
import { io } from 'socket.io-client';
class WebSocketClient {
constructor(url, token) {
this.socket = io(url, {
auth: { token },
reconnection: true,
reconnectionDelay: 1000,
reconnectionAttempts: 5
});
this.messageQueue = [];
this.setupListeners();
}
setupListeners() {
this.socket.on('connect', () => {
console.log('Connected');
this.flushQueue();
});
this.socket.on('disconnect', (reason) => {
console.log('Disconnected:', reason);
});
this.socket.on('message', (msg) => {
this.onMessage?.(msg);
});
}
joinRoom(roomId) {
this.socket.emit('join-room', roomId);
}
send(roomId, content) {
if (this.socket.connected) {
this.socket.emit('message', { roomId, content });
} else {
this.messageQueue.push({ roomId, content });
}
}
flushQueue() {
while (this.messageQueue.length > 0) {
const msg = this.messageQueue.shift();
this.socket.emit('message', msg);
}
}
}
function useWebSocket(url) {
const [socket, setSocket] = useState(null);
const [connected, setConnected] = useState(false);
const [messages, setMessages] = useState([]);
useEffect(() => {
// getToken() is a user-supplied helper that returns the current auth token
// Example implementations:
// - From localStorage: () => localStorage.getItem('authToken')
// - From context: () => authContext.token
// - From cookie: () => document.cookie.split('token=')[1]
const ws = io(url, { auth: { token: getToken() } });
ws.on('connect', () => setConnected(true));
ws.on('disconnect', () => setConnected(false));
ws.on('message', (msg) => {
setMessages(prev => [...prev, msg]);
});
setSocket(ws);
return () => ws.disconnect();
}, [url]);
const send = useCallback((roomId, content) => {
socket?.emit('message', { roomId, content });
}, [socket]);
return { connected, messages, send };
}
interface Message {
type: 'message' | 'typing' | 'presence';
roomId: string;
userId: string;
content?: string;
timestamp: number;
}
// Acknowledge delivery
socket.emit('message', data, (ack) => {
if (ack.success) console.log('Delivered');
});
See references/python-websocket.md for:
| Connections | Architecture |
|---|---|
| <10K | Single server |
| 10K-100K | Redis pub/sub |
| >100K | Sharded Redis + load balancer |
// Express endpoints for operational visibility
app.get('/api/ws/stats', (req, res) => {
res.json({
activeConnections: io.sockets.sockets.size,
rooms: [...io.sockets.adapter.rooms.keys()],
users: users.size
});
});
app.get('/api/ws/health', (req, res) => {
res.json({
status: 'healthy',
uptime: process.uptime(),
memoryUsage: process.memoryUsage()
});
});