usage: knock [-h] [-t TIMEOUT] [-d DELAY] [-u]
             host port[:protocol] [port[:protocol] ...]

Simple port-knocking client written in python3. See more at
https://github.com/grongor/knock

positional arguments:
  host                  Hostname or IP address of the host to knock on.
                        Supports IPv6.
  port[:protocol]       Port(s) to knock on, protocol (tcp, udp) is optional.

optional arguments:
  -h, --help            show this help message and exit
  -t TIMEOUT, --timeout TIMEOUT
                        How many milliseconds to wait on hanging connection.
                        Default is 200 ms.
  -d DELAY, --delay DELAY
                        How many milliseconds to wait between each knock.
                        Default is 200 ms.
  -u, --udp             Use UDP instead of TCP by default.