WebSockets and Real-Time

import { WebSocketServer, WebSocket } from 'ws';

const wss = new WebSocketServer({ port: 0 });

wss.on('connection', (socket) => {
  socket.send(JSON.stringify({ type: 'welcome', text: 'Connected' }));
  socket.on('message', (data) => {
    const msg = JSON.parse(data);
    if (msg.type === 'ping') socket.send(JSON.stringify({ type: 'pong', at: msg.at }));
    else socket.send(JSON.stringify({ type: 'echo', text: msg.text.toUpperCase() }));
  });
});

wss.on('listening', () => {
  const client = new WebSocket(`ws://localhost:${wss.address().port}`);
  let received = 0;
  client.on('open', () => {
    client.send(JSON.stringify({ type: 'chat', text: 'hello there' }));
    client.send(JSON.stringify({ type: 'ping', at: 1 }));
  });
  client.on('message', (data) => {
    console.log(JSON.parse(data));
    if (++received === 3) {
      client.close();
      wss.close();
    }
  });
});

import { WebSocketServer, WebSocket } from 'ws';

const rooms = new Map();
const wss = new WebSocketServer({ port: 0 });

function join(socket, room) {
  if (!rooms.has(room)) rooms.set(room, new Set());
  rooms.get(room).add(socket);
  socket.room = room;
}

function broadcast(room, message) {
  for (const s of rooms.get(room) ?? []) {
    if (s.readyState === WebSocket.OPEN) s.send(JSON.stringify(message));
  }
}

wss.on('connection', (socket) => {
  socket.on('message', (data) => {
    const msg = JSON.parse(data);
    if (msg.type === 'join') join(socket, msg.room);
    if (msg.type === 'say') broadcast(socket.room, { room: socket.room, from: msg.from, text: msg.text });
  });
  socket.on('close', () => rooms.get(socket.room)?.delete(socket));
});

wss.on('listening', async () => {
  const url = `ws://localhost:${wss.address().port}`;
  const connect = (name, room) => new Promise((resolve) => {
    const ws = new WebSocket(url);
    ws.on('open', () => { ws.send(JSON.stringify({ type: 'join', room })); resolve(ws); });
    ws.on('message', (d) => console.log(`${name} got:`, d.toString()));
  });
  const ada = await connect('ada', 'kitchen');
  const ben = await connect('ben', 'kitchen');
  const cy = await connect('cy', 'garden');
  await new Promise((r) => setTimeout(r, 50));
  ada.send(JSON.stringify({ type: 'say', from: 'ada', text: 'Kettle is on' }));
  await new Promise((r) => setTimeout(r, 50));
  for (const ws of [ada, ben, cy]) ws.close();
  wss.close();
});

import { createServer } from 'node:http';

const server = createServer((req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    Connection: 'keep-alive',
  });
  let n = 0;
  const timer = setInterval(() => {
    n++;
    res.write(`event: progress\ndata: ${JSON.stringify({ percent: n * 25 })}\n\n`);
    if (n === 4) {
      clearInterval(timer);
      res.end();
    }
  }, 20);
  req.on('close', () => clearInterval(timer));
});

server.listen(0, async () => {
  const r = await fetch(`http://localhost:${server.address().port}/export-progress`);
  const text = await r.text();
  const updates = text.trim().split('\n\n').map((block) => JSON.parse(block.split('data: ')[1]).percent);
  console.log(r.headers.get('content-type'));
  console.log(updates.join('% ') + '%');
  server.close();
});