Firewall issues
Security software such as Windows Firewall or ZoneAlarm will block all unused ports. If the ports used by BiblioRemote are blocked, you won't be able to access BiblioRemote from other computers. You will need to change the appropriate settings in your security software to unblock those ports. By default, BiblioRemote uses ports 12005 and 12006.
Running behind a router
If you run BiblioRemote on a computer behind a router and only the router has an IP open to the world, please make sure the two ports 12005 and 12006 are not blocked by the router. Also, configure your router to forward traffic on those two ports to the computer on which BiblioRemote runs. For example, if that computer's IP address is "192.168.0.3", configure the router (this is sometimes called “port forwarding”) so that it sends all traffic it receives from the Internet for ports 12005 and 12006 to "192.168.0.3".