A Port Knocking C-based server & client. Stealth mode by closed ports, strong encryption (ARC4 & BlowFish), Daemon mode, compresed sequence, MD5 digest log check, user passwords and user privelege system, action triggers... GPL license.
The doorman guards the door of a server, manipulating firewall rules to admit only recognized parties.
Allows Silent Running - a server with all ports CLOSED.
Linux-BSD-OSX server & client; C source & docs + Windows client binary. GPL.