Client

$(function() {

  var socket = io.connect('/speaker');
  socket.on('connect', function() {
    // send session to server  
    socket.emit('join', { session_id: session.get('id') });

    socket.on('join.success', function(data) {
      $(document).on('deck.change', slideChange);
    });

    socket.on('join.failure', function(data) {
      console.log(data);
    });
  });

  socket.on('slide.change', function(data) {
    $(document).off('deck.change', slideChange);
    $.deck('go', data.to);
    $(document).on('deck.change', slideChange);
  });

  socket.on('disconnect', function() {
    console.log('Oh boy, that is not good!');
  });

  var slideChange = function(event, from, to) {
    socket.emit('slide.change', { session_id: session.get('id'), from: from, to: to });
  }

});

Server

io.of('/speaker').on('connection', function(socket) {
  
  socket.on('join', function(data) {
    var session_id = data.session_id,
        session = global.sessions.get(session_id);

    if(session) {
      // socket joins session room
      socket.join(session_id);


      socket.emit('join.success', { 'you': { 'id': 1 } });

      // allow slide change
      socket.on('slide.change', function(data) {
        session.set('slide', data.to);
        socket.broadcast.to(session_id).emit('slide.change', data);
      });

    } else {
      socket.emit('join.failure', { 'reason': 'Fuck off, dude!' });
    }

  });

});