firedoor forwards any TCP connection behind a firewall using techniques similar to reverse telneting. Written in Java 1.4, so it is very small and can run on both Linux and Win32 without modifications. Source file included.
You can download it from the following link: https://packetstormsecurity.com/files/download/31528/firedoor-0.2.tar.gz
Source: https://packetstormsecurity.com/files/31528/firedoor-0.2.tar.gz.html