Nodejs real time online user counter

I have a website and implemented a real time online user counter using nodejs and socket.io. Here is the code:

$io.on('connection', function (socket) {

    var $ip_address = socket.handshake.address;
    if ($ips_connected.hasOwnProperty($ip_address)) {
        $ips_connected[$ip_address]++;
    } else {
        $ips_connected[$ip_address] = 1;
        $connected_users++;


        if ($connected_users > $max_users)
            $max_users = $connected_users;
    }

    socket.emit('update', $connected_users);

    socket.on('disconnect', function () {
        if ($ips_connected.hasOwnProperty($ip_address)) {
            $ips_connected[$ip_address]--;
            if ($ips_connected[$ip_address] <= 0) {
                delete $ips_connected[$ip_address];
                $connected_users--;
            }
        }
    });

    socket.on('update', function () {
        socket.emit('update', $connected_users);
    });

});

As you can see, i do not consider multiple conections by the same ip address. The problem with this code is that Google Analytics Real Time data are showing a number smaller than that calculate by nodejs.

What i need is a explanation of someone who have already implemented something like this using nodejs to tell me if i can trust on this code or should i trust on Analytics real time counter. I'm showing to my users the number of users connected to my website at the moment using this code, so i dont want to display wrong numbers.

UPDATE

I forgot to say that analytics are showing numbers like 30 units less than my own counter.