Knock is a port-knocking server/client. Port-knocking is a method where a server can sniff one of its interfaces for a special "knock" sequence of port-hits. When detected, it will run a specified event bound to that port knock sequence. These port-hits need not be on open ports, since we use libpcap to sniff the raw interface traffic.
This is a companion discussion topic for the original entry at https://copr.fedorainfracloud.org/coprs/jujens/knock/