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Last active April 26, 2024 11:15
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Server-Sent Events nodejs example. This shows how to detect the client disconnection.
var express = require('express');
var app = express();
// response header for sever-sent events
const SSE_RESPONSE_HEADER = {
'Connection': 'keep-alive',
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'X-Accel-Buffering': 'no'
};
// Connected users (request object of each user) :
var users = {};
// SSE starting endpoint
// You can access url `http://localhost:3000/sse/<userId>`
//
// Caution:
// This example exposes <userId> as URI parameter for testing purpose.
// In reality, you should use one stored in req.session.
app.get('/sse/:userId', function(req, res) {
let userId = getUserId(req);
// data for sending
let data;
// Stores this connection
users[userId] = req;
// Writes response header.
res.writeHead(200, SSE_RESPONSE_HEADER);
// Interval loop
let intervalId = setInterval(function() {
console.log(`*** Interval loop. userId: "${userId}"`);
// Creates sending data:
data = {
userId,
users: Object.keys(users).length,
// memoryUsage: process.memoryUsage()
time: new Date().getTime(),
};
// Note:
// For avoidance of client's request timeout,
// you should send a heartbeat data like ':\n\n' (means "comment") at least every 55 sec (30 sec for first time request)
// even if you have no sending data:
if (!data)
res.write(`:\n\n`);
else
res.write(`data: ${JSON.stringify(data)}\n\n`);
}, 3000);
// Note: Heatbeat for avoidance of client's request timeout of first time (30 sec)
res.write(`:\n\n`);
req.on("close", function() {
let userId = getUserId(req);
console.log(`*** Close. userId: "${userId}"`);
// Breaks the interval loop on client disconnected
clearInterval(intervalId);
// Remove from connections
delete users[userId];
});
req.on("end", function() {
let userId = getUserId(req);
console.log(`*** End. userId: "${userId}"`);
});
});
function getUserId(req) {
// Note:
// In reality, you should use userId stored in req.session,
// but not URI parameter.
return req.params.userId;
}
app.listen(3000, function() {
console.log('Example app listening on port 3000!');
});
@arnaudambro
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arnaudambro commented Feb 21, 2020

@abhinavchawla13
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@arnaudambro, thanks 😄

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