server.js

var server = require('http').createServer(),
    io     = require('socket.io')(server),
    logger = require('winston'),
    port   = 3000;


// Logger config
logger.remove(logger.transports.Console);
logger.add(logger.transports.Console, { colorize: true, timestamp: true });
logger.info('SocketIO > listening on port ' + port);

var clients = {};

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

    //Regiter a client based on userid
    socket.on('register', function(data)
    {
        if (clients[data.userId] && clients[data.userId].sockets instanceof Array)
        {
            //if user is already registered
            //with one or many socket clients,
            //just push socket id to array of sockets
            clients[data.userId].sockets.push(socket.id);

        } else 
        {
            //if it is the first socket client
            //add an array and push socket id
            clients[data.userId] = { sockets: []};

            clients[data.userId].sockets.push(socket.id);
        }

        logger.info('SocketIO > New connection -> userId = ' + data.userId +' socketId = ' + socket.id);

    });    

    socket.on('broadcast', function (data) {

        //when LAMP server broadcast look for user in list of clients
        if(clients[data.userId])
        {
            for(var soct in clients[data.userId].sockets){

                //proxy event to all connected sockets
                io.sockets.connected[clients[data.userId].sockets[soct]].emit(data.receiverId, data);

                logger.info('New data was sent = ' + JSON.stringify(data));
            }
        }
        else
        {
          logger.info('UserId is not open for comunication: ' + data.userId);  
        }
        
    });

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

        //when socket  disconnects remove socket from list of sockets
        for(var name in clients){

            for (var soct in clients[name].sockets){

                if(clients[name].sockets[soct] === socket.id)
                {
                    //remove socket from array of sockets
                    clients[name].sockets.splice(soct, 1);

                    logger.info('socket removed');

                    //if no more sockets are connected
                    //remove user from list of clients
                    if (clients[name].sockets.length === 0)
                    {
                        delete clients[name];

                        logger.info('userId completely removed');
                    }
                    break;
                }


            }


        }
        
    });

});



server.listen(port);