onclose not called if a client disconnects due to network failure

[pavan4]

I am listening to the close event from a client on a node server using websocket.on('close', function close() { } );

However, the callback is not being fired if a client gets disconnected due to network failure.

Is there any way to detect dead connections on the server side ?

[pavan4]

https://github.com/FlorianBELLAZOUZ/ws/tree/KeepAlive This provides an implementation for the above issue

[urosjarc]

@pavan4 I have the same issue, your implementation is quite good... I suggest developers to merge in master... 👍

[pavan4]

@urosjarc The implementation I mentioned above does this out of the box for you with pings but it doesnt work on ubuntu 14.0.4 and the timeout on tcp defaults to 30s always. Pings to the client result in error and are crashing the server, I am not able to rely on the pings.

[urosjarc]

Then what are your suggestions? I know only pings checking if connection is alive...

[pavan4]

I am planning to use https://github.com/theturtle32/WebSocket-Node This package has similar performance as ws and provides a onclose notification when the client disconnects

[urosjarc]

Did you check onclose method for network drop, does it really emit?

[r-pr]

I've got the same problem with detecting connections experiencing network errors. I've tried setting keepAlive, as pointed here, but close event still fired only 10 s after network got down. Finally, I figured out how to use Websocket ping-pong mechanism:

var WebSocketServer = require('ws').Server,
    wss = new WebSocketServer({ port: 4444 });

var PONG_TIMEOUT = 1500; //client has 1.5s to respond with pong

wss.on('connection', function connection(ws) {
    var lastPongReceived = Date.now();
    ws._socket.on('data', function(data) {
        if (data[0] == 0x8a) { //opcode of pong response
            lastPongReceived = Date.now();
        }
    });

    var x = setInterval(function() {
        if (Date.now() - lastPongReceived > PONG_TIMEOUT) {
            console.log('pong timeout elapsed');
            //...code to run if connection unavailable
            clearInterval(x);
            ws._socket.destroy(); //ws.close() won't raise 'close' event, because close message 
                                   //cannot be delivered to client      
        }
        if (ws.readyState === 1) {
            ws.ping('.', false);
        } 
    }, 1000);

    ws.on('close', function() {
        console.log('connection closed');
    })
});

[john-doherty]

@r-pr how has the above ping/pong code worked out for you? Have you used it in production and if so how many connections? Thanks!

[urosjarc]

This is my implementation:
https://github.com/urosjarc/websocketRest.js
It's used in production for 1 year +2000 mobile devices connected which are switching connections (wifi, 3G) all the time. We were having many problems with duplicats but now this lib is running 1 year without error.
This is the company that use this lib: http://facilityforhotels.com/

[urosjarc]

I will add additional docs if there will be an interest in this lib.

[r-pr]

@john-doherty It seems that the mechanism does the job, but I haven't used it in production.

[john-doherty]

@r-pr I'm going to use a slightly modified version of your concept. I'll let you know how it goes.

[r-pr]

@john-doherty OK

[zs9024]

has the issue been solved in the latest version?

[lpinca]

A possible way to handle this issue is illustrated here: https://github.com/websockets/ws#how-to-detect-and-close-broken-connections.
Closing, feel free to continue discussing on the closed thread.