This is a simple implementation of Port Knocking techniques. It sniffs network packets looking for predetermined keys and executes commands to open and close ports on the firewall. In the client mode it injects packets with the key to server.
You can download it from the following link: https://packetstormsecurity.com/files/download/41257/coarseknocking-0.0.2.tar.gz
Source: https://packetstormsecurity.com/files/41257/coarseknocking-0.0.2.tar.gz.html