knock (1) Linux Manual Page
NAME
knock – port-knock client
SYNOPSIS
knock [options] <host> <port[:proto]> [port[:proto]] …
DESCRIPTION
knock is a port-knock client. It sends TCP/UDP packets to each specified port on host, creating a special knock sequence on the listening server (see the knockd manpage for more info on this).
OPTIONS
-u, –udp- Make all port hits use UDP (default is TCP). If you want each port to use a different protocol (TCP or UDP), then you can specify the protocol on a per-port basis. See the example below.
-d <t>, –delay <t>- Wait <t> milliseconds between each port hit. This can be used in situations where a router mistakes your stream of SYN packets as a port scan and blocks them. If the packet rate is slowed with –delay, then the router should let the packets through.
-v, –verbose- Output verbose status messages.
-V, –version- Display the version.
-h, –help- Syntax help.
EXAMPLES
knock myserver.example.com 123:tcp 456:udp 789:tcp knock -u myserver.example.com 8284 4721 18592 42912
SEE ALSO
knockd is the accompanying port-knock server.
AUTHOR
Judd Vinet <jvinet [at] zeroflux.org>