rinetd allows fast, reliable port forwarding even behind existing routers and firewalls. A simple config file (/etc/rinetd.conf) with 4 entries per line:

listening-ip listening-port forward-to-ip forward-to port

is all the configuration needed.

ipfw only allows 1-hop port forwarding (useless behind a firewall router). rinetd is the solution.

Compliation tips/port would be greatly appreciated!