My XP experience is a little limited so these are just suggestions
Start your mud, and in a command shell use netstat -an (the n is to speed it up, else it'll try resolving to the dns name for every entry in the list, which can take time, using the IPs should be good enough) to list all the listening and connected links. You should find there is a listening port for you mud on the port its supposed to use. If not, then you aren't binding and listening to the socket right.
If there is something listed, it will tell you which IP you have bound. If its 0.0.0.0 it has bound all available, otherwise it'll use 127.0.0.1 or the IP for your NIC or other devices as and if they have anything assigned.