I'm trying to set up a permanent Minecraft server on a desktop I have here at college. However, the IP is dynamic. I've successfully connected to it using my laptop (using the IPv4 address I usually would), however when I had a friend try it in another town, he got the "connection refused" (or something close to that) message. I was informed by someone here that if I typed in the hostname of the computer I was using I SHOULD be able to connect regardless of the ever-changing IP, but this doesn't seem to be true, and I get the "Failed to connect to server. Unknown host..." error.
The desktop is running Windows 7 Home Premium.
You most likely will not be able to host a server from within the college's network. People connected to your network will be able to find you, but outsiders won't. You have to set up port forwarding on the routers for the school's network. No college is going to open a port (which is very insecure) so you can play a game. You should send the server files to a friend to host from his/her home PC so you can play.
You can apply for a free account at dyndns.com, assuming the game can connect via domain name as well as IP. You would just have to give out the domain name and make sure the information at dyndns.com is updated when your IP changes.