SSE endpoint for server-to-browser events

7308 views

                  import type { Request, Response } from 'express';

export function eventsSse(_req: Request, res: Response) {
  res.setHeader('Content-Type', 'text/event-stream');
  res.setHeader('Cache-Control', 'no-cache, no-transform');
  res.setHeader('Connection', 'keep-alive');

  res.flushHeaders?.();

  const heartbeat = setInterval(() => {
    res.write(': heartbeat

');
  }, 15_000);

  res.write(`event: ready
data: ${JSON.stringify({ ok: true })}

`);

  res.on('close', () => {
    clearInterval(heartbeat);
    res.end();
  });
}

When I want ‘real time’ updates without the operational overhead of WebSockets, I reach for Server-Sent Events (SSE). It’s just streaming HTTP, so it behaves well behind proxies and is easy to reason about. I set the right headers (Content-Type: text/event-stream), flush early, and send heartbeat comments so intermediaries don’t silently close idle connections. On the client, EventSource gives me a simple reconnect story, and I add exponential backoff when needed. The key constraint is that SSE is server → client only, but for progress updates, notifications, and status streams, that’s exactly the shape I want. It’s boring, simple, and surprisingly effective.

Mateo Rodriguez

More from Mateo Rodriguez

SSE endpoint for server-to-browser events

0 Comments

More from Mateo Rodriguez