If you wish to test your AI against other AIs then you'll need a DAIDE server. Servers can run either on the same machine or a seperate machine to your AI.
David Norman's DAIDE Server
AiServer is the original DAIDE server, run from the desktop. It is used by both the AI and Real-Time communities as the reference implementation.
Andrew Rose's DAIDE Test Server (v00.03.0462)
The test server is a development aid and comes as part of the utilities package. It allows you to set up particular test positions for your AI and check that it generates the expected results.
Eric Wald's Brainshell
An online server.
Peter Lund's Maginot
Maginot is a permanent RT server that is constantly up and prepared to serve the internet. Players connect using a java client (available from the site), or David Norman's Mapper.