This is the Four In A Line Server by Michael Kliewe.
The server is written in PHP and has an API that you can use to create your own client and play against the server.
On this website you can play online against the server, see a history of all games played in the past, download a PHP client, read how to create your own client to play against the server on the console or create an intelligent player in PHP.
If you have any hints, comments, questions or problems, please contact me:
There is also a german blog post about this project, where you can discuss with other users and ask questions.