socket.io: disconnect event isn't fired


Question

I have made a simple realtime visitor counter.

You can download it from this repository.

What happens is that disconnect event (even after browser closing) on server is never fired.

server.js is:

(function () {
var app, count, express, io;

express = require('express');
io = require('socket.io');

app = module.exports = express.createServer();

app.configure(function () {
    app.set('views', __dirname + '/views');
    app.set('view engine', 'jade');
    app.use(express.bodyParser());
    app.use(express.methodOverride());
    app.use(require('stylus').middleware({
        src: __dirname + '/public'
    }));
    app.use(app.router);
    return app.use(express.static(__dirname + '/public'));
});

app.configure('development', function () {
    return app.use(express.errorHandler({
        dumpExceptions: true,
        showStack: true
    }));
});
app.configure('production', function () {
    return app.use(express.errorHandler());
});

io = require('socket.io').listen(app);

count = 0;

io.sockets.on('connection', function (socket) {
    count++;
    io.sockets.emit('count', {
        number: count
    });
});

io.sockets.on('disconnect', function () {
    console.log('DISCONNESSO!!! ');
    count--;
    io.sockets.emit('count', {
        number: count
    });
});


app.get('/', function (req, res) {
    return res.render('index', {
        title: 'node.js express socket.io counter'
    });
});
if (!module.parent) {
    app.listen(10927);
    console.log("Express server listening on port %d", app.address().port);
}

}).call(this);

Script on the client is:

    script(type='text/javascript')

        var socket = io.connect();

        socket.on('count', function (data) {
            $('#count').html( data.number );
        });
1
31
5/27/2013 2:25:49 PM

Accepted Answer

Put your on disconnect code inside your on connect block and edit it a bit like so:

io.sockets.on('connection', function (socket) {
    count++;
    io.sockets.emit('count', {
        number: count
    });

    socket.on('disconnect', function () {
        console.log('DISCONNESSO!!! ');
        count--;
        io.sockets.emit('count', {
            number: count
        });
    });
});

This way you're detecting when a specific socket (specifically the socket you pass to your anonymous function that is run on connection) is disconnected.

50
4/26/2012 11:02:43 PM

From Socket.IO 1.0 the io.engine.clientsCount property is available. This property tells you how many open connection does your app currently have.

io.sockets.on('connection', function (socket) {
    io.sockets.emit('count', {
        number: io.engine.clientsCount
    });

    socket.once('disconnect', function () {
        io.sockets.emit('count', {
            number: io.engine.clientsCount
        });
    });
});

Note: Use .once instead of .on and the listener will be removed automatically from the socket what is good for us now, because the disconnect event is only fired once per socket.


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