dc++ software
 

there are a couple different things I'm trying to do in this project.

dc++ server - I've found a few different packages for linux to run dc++ servers, but I'm not sure how to do what I'd like to, or if it can even be done. I would like to allow only registered users to connect to the server, then I'd like to write a php script to register new accounts by invitation only.

a lower priority part of the project, I'm looking for a dc++ client that can run from command line on a server and do nothing but serve files. this way, it's not putting any strain on my desktop computer.

is there software that I could do this with?

Have you checked out MlDonkey?

It has support for DC++ and runs as a daemon which you can connect to with a variety of clients, somewhat like MPD. On the server side I am not sure though, haven't configured a DC++ server before.