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How do you implement Server-Sent Events (SSE) in Node.js?

Q: How do you implement Server-Sent Events (SSE) in Node.js?

**TL;DR.** **SSE** keeps a single HTTP response open with Content-Type: text/event-stream and writes data: ...\n\n frames to **push updates one-way** (server→client). The browser consumes it with EventSource , which **auto-reconnects**. It's simpler than WebSockets when you only need server-to-client streaming. server data: {...} (stream) one-way, auto-reconnect <text class='d-text' x='382' y='78' text-anchor='midd

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One-way server push over a long-lived HTTP response.

nodejssserealtimestreaming

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An SSE endpoint

app.get('/events', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    Connection: 'keep-alive',
  });
  const timer = setInterval(() => {
    res.write(`data: ${JSON.stringify({ t: Date.now() })}\n\n`);
  }, 1000);
  req.on('close', () => clearInterval(timer));   // cleanup
});

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