express_server_sent_events_endpoint_with_periodic_updates.ts

1import express, { Request, Response } from 'express';
2import cors from 'cors';
3
4const app = express();
5const PORT = 3000;
6
7app.use(cors());
8app.use(express.json());
9
10/**
11 * SSE Endpoint
12 */
13app.get('/events', (req: Request, res: Response) => {
14    // 1. Set necessary headers for SSE
15    res.setHeader('Content-Type', 'text/event-stream');
16    res.setHeader('Cache-Control', 'no-cache');
17    res.setHeader('Connection', 'keep-alive');
18
19    // 2. (Optional) Disable buffering for Nginx/Proxies
20    res.setHeader('X-Accel-Buffering', 'no');
21
22    // Send an initial connection event
23    res.write('data: Connection established\n\n');
24
25    // 3. Setup an interval to send periodic updates
26    const intervalId = setInterval(() => {
27        const data = {
28            time: new Date().toLocaleTimeString(),
29            message: 'Hello from Server-Sent Events!'
30        };
31        
32        // SSE format: "data: <string>\n\n"
33        res.write(`data: ${JSON.stringify(data)}\n\n`);
34    }, 2000);
35
36    // 4. Handle client connection close
37    req.on('close', () => {
38        console.log('Client closed connection');
39        clearInterval(intervalId);
40        res.end();
41    });
42});
43
44app.listen(PORT, () => {
45    console.log(`SSE Server running at http://localhost:${PORT}/events`);
46});