Opening a Port

I didn’t even know you could listen to other people’s music with iTunes but apparently you can. So there’s all these playlists I want to check out and stuff but iTunes is telling me that my port 3689 isn’t open. As far as I can tell I don’t have a firewall running and I doubt the hotel I’m staying at would just randomly block that port. So is there some system tool I can use to open ports or what? I’m a confused little man.