How do I catch a WebSocket connection interruption?

Question

In Firefox (at least), if you hit ESC, then it will close all open WebSockets connections. I need to capture that disconnection and try to re-connect once it's available again.

Here's an example of the code I've tried to implement, but nothing I can figure out will catch the error and allow me to handle it gracefully.

Have a look at the code: http://jsfiddle.net/w5aAK/

var url = "ws://echo.websocket.org";
    try {
        socket = window['MozWebSocket'] ? new MozWebSocket(url) : new WebSocket(url);
        socket.onopen = function(){
            console.log('Socket is now open.');
        };
        socket.onerror = function (error) {
            console.error('There was an un-identified Web Socket error');
        };
        socket.onmessage = function (message) {
            console.info("Message: %o", message.data);
        };
    } catch (e) {
        console.error('Sorry, the web socket at "%s" is un-available', url);
    }

setTimeout(function(){
    socket.send("Hello World");
}, 1000);

Turn on your console and watch the output.

Am I doing something wrong here, or is it just not possible because the connection is running outside of the scope of the JS script?

Any input would be helpful.

Thanks!

You should call `socket.send()` within the `onopen` callback, cause a connection may still not be established after 1 second. — neevek, Nov 29 '12 at 01:31
I'm aware of that and know how to handle it, but that's not the question I'm asking. — Zach, Nov 29 '12 at 05:22

score 5 · Accepted Answer · answered Nov 29 '12 at 07:46

5

You can attach a handler to the socket.onclose event. It will be called when you hit ESC and the connection is interrupted.

See: http://jsfiddle.net/w5aAK/1/

One problem that you can't get around at the moment is the interrupted error being output to the console. There's no way of capturing that at the moment I'm afraid.

answered Nov 29 '12 at 07:46

leggetter

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1

Yeah, that's what I was afraid of, I just needed to verify it. I already have an `onclose` event to handle it, but was hoping to a void the exception. Thanks for your input! – Zach Nov 29 '12 at 15:50
6

_One problem that you can't get around at the moment is the interrupted error being output to the console._ Is there a referene to this in any specs or docs? – Max Ch Nov 30 '13 at 08:37

score 1 · Answer 2 · edited May 23 '17 at 11:45

You can't catch it and it's not your fault. It's FireFox bug. Vote for it here:

https://bugzilla.mozilla.org/show_bug.cgi?id=712329

I personally tried all kind of solutions:

event handlers onunload onbeforeunload onclose try..catch some js error handling 3rd party services etc.

You can log to console your socket, it's closed before unload, but FF thinks different.. :(

Solution (not answer directly to the answer, but it works):

It's a bug, so you can't catch, but this info is not Solution. After all kind of crazy workarounds and tries to catch that bug, i finally found this working. If you use socket.io to work with WebScokets it can work with different transport technologies. xhr-polling works with Firefox.

if (/Firefox[\/\s](\d+\.\d+)/.test(navigator.userAgent)) { //test for Firefox/x.x     or Firefox x.x (ignoring remaining digits);
    socket = io.connect('//' + node_server + '/', {
        transports: ['polling']
    });
} else {
    socket = io.connect('//' + node_server + '/');
}

What helped me - might help you too:

Web Socket support in Node.js/Socket.io for older browser

Define transport types on the client side

socket.io doens't work with transports: [ 'xhr-polling' ]

How do I catch a WebSocket connection interruption?

2 Answers2

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