Why websocket server closes connections?

Question

I have websocket nodejs server with ~2000 concurrent connections and server closes them periodically. I don't know the reason. I catch it in my client code

 this.ws.onclose = function(){
        //try to reconnect in 5 seconds
        console.log("WS CLOSED. RECONNECT IN 5 SECS");
        setTimeout(function(){self.startNative()}, 5000);
    };

I start server with following code

var WebSocketServer = require('ws');

//start websockets server
var webSocketServer = new WebSocketServer.Server({port: config.port2}, function () {
    console.log("Native websocket server process running on " + config.port2);
});

//websockets connection
webSocketServer.on('connection', function(ws, req) {
    ws.on('close', function() {
        //somecode
    });

What can cause it ?

Maybe this can help [How many socket connections possible?](https://stackoverflow.com/questions/651665/how-many-socket-connections-possible) — Arsenio Siani, Feb 16 '18 at 11:08
Are the channels sitent for long time? Try add a heartbeat/ping on a timed schedule. — Arsenio Siani, Feb 16 '18 at 11:10
@ArsenioSiani thx, but client can reconnect in 5 seconds, in 10 seconds, simultaneously — socm_, Feb 16 '18 at 11:25
@socm_ can not understand your comment, you are complaining about the connection closed (when you want them alive). How long the socket connection stay _connected_ before it closes? — Arsenio Siani, Feb 19 '18 at 09:06

score 2 · Answer 1 · answered Feb 16 '18 at 11:15

Middleboxes on the internet will close connections that have seen no data for a long time (many minutes or hours). You can resolve this by sending a "heartbeat" packet periodically, say once per five minutes.

It does not matter which direction originates the heartbeats, and the other side does not need to explicitly reply (but it could). If the server is the one who sends heartbeats, this will also help the server to prune dead connections sooner.

Why websocket server closes connections?

1 Answers1