knock(1) on Linux
The text 94e905812a87, as Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch) shipped it.
port-knock client
Flags it lists
-
--help -
--udp -
--verbose -
--version -
-V -
-h -
-u -
-v