Knock-Out is a remote administration tool using port-knocking techniques. It supports both UDP and TCP transmission and is customizable. It allows both bind ports and reverse shells. Note that all documentation, etc, is written in Spanish.
You can download it from the following link: https://packetstormsecurity.com/files/download/52834/knock-out.tar.gz
Source: https://packetstormsecurity.com/files/52834/knock-out.tar.gz.html