tcpdchk -v (return code: 0)
Using network configuration file: /etc/inetd.conf
tcpdchk --help (return code: 1)
tcpdchk: invalid option -- '-'
usage: tcpdchk [-a] [-d] [-i inet_conf] [-v]
-a: report rules with implicit "ALLOW" at end
-d: use allow/deny files in current directory
-i: location of inetd.conf file
-v: list all rules