arbitrary TCP and UDP connections and listens

-l      Used to specify that nc should listen for an incoming connection rather than initiate a connection
        to a remote host.  It is an error to use this option in conjunction with the -p, -s, or -z options.
        Additionally, any timeouts specified with the -w option are ignored.

-p source_port
        Specifies the source port nc should use, subject to privilege restrictions and availability.  It is
        an error to use this option in conjunction with the -l option.