pknlusr — userspace monitor for successful xt_pknock matches
pknlusr [group-id]
xt_pknock is an xtables match extension that implements so-called port knocking. It can be configured to send information about each successful match via a netlink socket to userspace. pknluser listens for these notifications.
By default, pknlusr listens for messages sent to netlink multicast group 1. Another group ID may be passed as a command-line argument.
xtables-addons(8)