WebSocket

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len |    Extended payload length    |
|I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
|N|V|V|V|       |S|             |   (if len==126/127)           |
| |1|2|3|       |K|             |                               |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
|     Extended payload length continued (if len==127)          |
+ - - - - - - - - - - - - - - - +-------------------------------+
|                               |Masking-key (4 bytes, client→server)|
+-------------------------------+-------------------------------+
| Masking-key (continued)       |          Payload Data         |
+-------------------------------+-------------------------------+

npm install ws

import WebSocket, { WebSocketServer } from 'ws';

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

wss.on('connection', (ws, req) => {
  const ip = req.headers['x-forwarded-for'] || req.socket.remoteAddress;
  console.log(`客户端已连接: ${ip}`);

  ws.on('message', (data) => {
    const msg = JSON.parse(data.toString());
    broadcast(msg); // 见下方广播实现
  });

  ws.on('close', () => console.log('客户端断开'));
  ws.on('error', (err) => console.error('WS 错误:', err));
});

function broadcast(payload) {
  const text = JSON.stringify(payload);
  for (const client of wss.clients) {
    if (client.readyState === WebSocket.OPEN) client.send(text);
  }
}

const rooms = new Map();

wss.on('connection', (ws) => {
  ws.on('message', (raw) => {
    const { type, room, user, content } = JSON.parse(raw.toString());
    if (type === 'join') {
      if (!rooms.has(room)) rooms.set(room, new Set());
      rooms.get(room).add(ws);
      ws.room = room;
    }
    if (type === 'message') {
      for (const c of rooms.get(ws.room) ?? []) {
        c.send(JSON.stringify({ type: 'message', user, content }));
      }
    }
  });
  ws.on('close', () => rooms.get(ws.room)?.delete(ws));
});

const ws = new WebSocket('wss://example.com/chat');

ws.onopen = () => ws.send(JSON.stringify({ type: 'join', room: 'demo' }));
ws.onmessage = (e) => render(JSON.parse(e.data));
ws.onclose = () => console.log('连接关闭');

function send(content) {
  if (ws.readyState === WebSocket.OPEN) {
    ws.send(JSON.stringify({ type: 'message', content }));
  }
}

npm install socket.io

import { createServer } from 'node:http';
import { Server } from 'socket.io';

const io = new Server(createServer());
io.on('connection', (socket) => {
  socket.join('room:demo');                 // 服务端房间
  socket.on('chat', (msg) => {
    io.to('room:demo').emit('chat', msg);   // 仅房间内广播
  });
});
io.listen(3000);

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

const timer = setInterval(() => {
  for (const ws of wss.clients) {
    if (ws.isAlive === false) return ws.terminate();
    ws.isAlive = false;
    ws.ping();
  }
}, 30_000);

wss.on('close', () => clearInterval(timer));

function connect() {
  const ws = new WebSocket('wss://example.com/chat');
  ws.onclose = () => setTimeout(connect, 3_000); // 指数退避更佳
  return ws;
}

// v22+ 原生客户端
const ws = new WebSocket('wss://example.com/chat');
ws.addEventListener('open', () => ws.send('hello'));
ws.addEventListener('message', (e) => console.log(JSON.parse(e.data)));