Using Tryst, applications can discover what services are available on the
network, along with all necessary access information such as name, IP
address, and port number for a given service. 

Bonjour allows you to register a network service, such as a printer or file
server, so that it can be found by name or browsed for by service type and
domain.

LICENSE: BSD 2 clause / LGPL
Copyright (c) 2002 - 2006, Chris B. Vetter

WWW: http://gnustep.dyndns.org/