socket.io/node.js detecting if server is down

Question

Is there something that I can do on the client side to detect that the socket.io websocket is not available? Something along the lines of:

server starts as per usual
clients connect
messages are sent back and forth between server and client(s)
server shuts down (no longer available)
warn the connected clients that the server is not available

I tried to add the 'error' and 'connect_failed' options on the client side but without any luck, those didn't trigger at all. Any ideas from anyone how I can achieve this?

var sio = io.connect(); sio.socket.on('error', function (reason){ console.error('Unable to connect Socket.IO', reason); }); did you try? — Anh Tú
– Anh Tú, Commented May 9, 2013 at 3:58
Yes. I did try this - this is on the client side right? Also tried "connect_failed" but no luck. — Tamas
– Tamas, Commented May 9, 2013 at 4:06
Anh Tú's solution works when the client tries to connect to a server which is down. So basically one would need both scripts to cover all possible scenarios. — Nasim Khamidov
– Nasim Khamidov, Commented Apr 11, 2014 at 16:22

matthewtole · Accepted Answer · 2013-05-09 09:08:09Z

12

The disconnect event is what you want to listen on.

var socket = io.connect();

socket.on('connect', function () {
  alert('Socket is connected.');
});

socket.on('disconnect', function () {
  alert('Socket is disconnected.');
});

answered May 9, 2013 at 9:08

matthewtole

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1 Comment

joeytwiddle Over a year ago

I recommend also listening for the connect_error event suggested by cbautista. These two events are useful, but they will display nothing if the initial connection attempt fails.

Community · Accepted Answer · 2017-05-23 12:25:57Z

11

If you want to be able to detect that the client was not able to connect to the server, then try using connect_error. This works for me with socket.io-1.3.5.js. I found this in https://stackoverflow.com/a/28893421/2262092.

Here's my code snippet:

var socket = io.connect('http://<ip>:<port>', {
    reconnection: false
});
socket.on('connect_error', function() {
    console.log('Failed to connect to server');
});

edited May 23, 2017 at 12:25

CommunityBot

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answered Jul 23, 2015 at 23:39

cbautista

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Comments

Paprikash · Accepted Answer · 2016-07-16 14:58:33Z

0

hit this bug during my development and noticed my event calls were doubling up every time i reset the server, as my sockets reconnected. Turns out the solution that worked for me, which is not duping connections is this

var socket = io.connect();

socket.on('connect', function () {

console.log('User connected!');

});

socket.on('message', function(message) {

console.log(message);

});

( Found this at https://github.com/socketio/socket.io/issues/430 by KasperTidemann )

Turns out, it was becuase I put the 'message' listener inside the 'connect' function. Seating it outside of the listener, solves this problem.

Cheers to Kasper Tidemann, whereever you are.

Moving on!!

answered Jul 16, 2016 at 14:58

Paprikash

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Comments

user1274820 · Accepted Answer · 2018-04-20 19:48:41Z

0

connect_error didn't work for me (using Apache ProxyPass and returns a 503).

If you need to detect an initial failed connection, you can do this.

var socket;
try {
    socket = io();
}
catch(e) {
    window.location = "nodeServerDown.php";
}

Redirects the user to a custom error page when the server is down.

If you need to handle a disconnect after you've connected once.

You do this:

socket.on('disconnect', function() {
    //whatever your disconnect logic is
});

answered Apr 20, 2018 at 19:48

user1274820

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