Is Socket.IO multithreaded?

I have a server socket.iothat listens on sockets:

io.sockets.on('connection', function(socket){
    socket.on('myEvent', function(data){
        socket.emit('eventReceived', { status: 1 });
    });
});

Does this code work in multithreaded mode? if two clients throw an event myEvent, will it work simultaneously for both clients? or will it be processed one by one?

Many thanks!