socket.io open port concern

I have developed a live chat with socket.io. Now that all works well I am concerned about security. As far as I understand the next lines open port 3000 on my server.

 http.listen(3000, function(){
      console.log('listening on *:3000');
 });

If the port is open, anyone could just take a terminal and make a telnet request to that port. Is there a way to ask for a password or something to don't let everbody connect to the port? If there is, would my socket.io's app still works in the same way? Forgive my ignorance, I'm not a security expert.

via Sergi