The first release of the Q2sdb, or Quake II server database (though they point out "it isn't a real database") is now available. This is a "smallish" Java application which queries Quake II servers building an internal database of server information. Client applications can connect to this database and query for servers meeting certain criteria, such as a particular game or map name, or a server with a particular player. Here's a quote to describe what this can accomplish:

Since the server refreshing is done by the computer running Q2sdb, it can answer client queries simply by looking up information in its database. So if you just want to find out if your buddy (or clan) is playing (and where), why refresh the entire list of servers locally, when you can just query Q2sdb and have the answer in a second or two?

This code is capable of querying over 2000 Quake II servers per minute on a reasonable connection (384Kbit ADSL in my case), meaning the internal database is always quite fresh.

The code is very threaded, making it quite efficient. Each client connecting is handled in a separate thread so many clients can connect at once.

Also included is a sample client application called 'q2grep' which will display servers which match a number of given criteria.