lsnd is an ad-hoc server for Laser Squad Nemesis, which I hacked up as a stop-gap solution after the official server went down.

I have an instance running on my own machine - information on how to use it.

You can download the source, or clone it from its gitorious repo, if you're interested in seeing how it works. Using it to set up your own server would likely require a fair amount of experimentation and fiddling - I suggest you contact me directly if you want to do that, and I'll give some guidance.