Blinkd is a client/server pair, that lets the keyboard LEDs blink, indicating things like the number of incoming voice calls in the voice box or incoming faxes in the spool. Because client and server communicate via TCP/IP, they can be located on different machines. Do not use the software for vital purposes, as there is no security mechanism.
The first version of the software has been released 1998-06-28 as a Debian package, the latest version 2002-11-24. Look at the Debian package pages for stable, testing, and unstable. You may read the manual pages for the client and the server.