Occasionally, you need to test if tcp-ip traffic is being correctly routed to a specific port. When the protocol isn't useful for testing, try out this little tool.
Usage: echodaemon.pl <port number>
This little daemon simply listens on a give port, accepts connections, echoes any data is receives and closes the connection.
It's basic just for testing if firewalls and NAT rules are configured correctly. Once it's running, simply use a tool like telnet to connect to it.
NOTE: If you're using linux, you should really use the 'nc' (netcat) command. However, if you find yourself on AIX or Windows, this script could still be useful.