FileMaker Pro has a feature that allows client applications to auto-locate their server's IP address and connect to it. What is the best way to do this using a general purpose language like Java or .NET?
FileMaker probably is using Bonjour. Check at http://developer.apple.com/bonjour/ and also Avahi
It does so by implementing what they call multicast-dns. Using a P2P dns using multicast, they are able to show not only servers, but also servers and ports.
And even if you're using on an enterprise network, you can also publish records on the intranet dns server, so you are not going to rely on your routers and their multicast tolerance (which can be overwhelming). So, it scales up.