websocket-realtime

WebSocket and Real-Time Communication

Build production-ready WebSocket servers with reconnection, heartbeat, authentication, and horizontal scaling.

WebSocket Server (Node.js ws)

BAD: No connection lifecycle management.

import WebSocket, { WebSocketServer } from 'ws';

const wss = new WebSocketServer({ port: 8080 });

wss.on('connection', (ws) => {
  ws.on('message', (data) => {
    // Broadcast to everyone
    wss.clients.forEach((client) => {
      client.send(data);
    });
  });
});

GOOD: Connection tracking, error handling, graceful shutdown.

import WebSocket, { WebSocketServer } from 'ws';
import http from 'http';

interface Client {
  ws: WebSocket;
  userId: string;
  rooms: Set<string>;
  isAlive: boolean;
}

const server = http.createServer();
const wss = new WebSocketServer({ server });
const clients = new Map<WebSocket, Client>();

wss.on('connection', (ws, req) => {
  const client: Client = {
    ws,
    userId: '', // Set after auth
    rooms: new Set(),
    isAlive: true,
  };
  clients.set(ws, client);

  ws.on('pong', () => {
    client.isAlive = true;
  });

  ws.on('message', (data) => {
    try {
      const msg = JSON.parse(data.toString());
      handleMessage(client, msg);
    } catch (err) {
      ws.send(JSON.stringify({ error: 'Invalid message format' }));
    }
  });

  ws.on('error', (err) => {
    console.error('WebSocket error:', err);
  });

  ws.on('close', () => {
    clients.delete(ws);
  });

  ws.send(JSON.stringify({ type: 'connected' }));
});

// Heartbeat interval
const heartbeat = setInterval(() => {
  wss.clients.forEach((ws) => {
    const client = clients.get(ws);
    if (!client) return;

    if (!client.isAlive) {
      client.rooms.clear();
      clients.delete(ws);
      return ws.terminate();
    }

    client.isAlive = false;
    ws.ping();
  });
}, 30000);

// Graceful shutdown
process.on('SIGTERM', () => {
  clearInterval(heartbeat);
  wss.clients.forEach((ws) => {
    ws.close(1000, 'Server shutting down');
  });
  server.close(() => {
    process.exit(0);
  });
});

server.listen(8080);