Hey Wern,
Just a few thoughts:
a) window.now = nowInitialize("//localhost:8081", {}); will only work on your computer, I think you mentioned you were doing this, but you'll need to change "localhost" in this line to be your actual public facing ip
b) your operating system's firewall could be preventing incoming connections. On OS X this setting is in System Preferences > Security & Privacy > Firewall
c) you could try changing server.listen(8081, "0.0.0.0"); to just server.listen(8081);
HTH