IPipe ("internet pipe") is a program I wrote that is sort of like STunnel, except:

1. It's written in Java and takes advantage of the SSL support that is already in Java. You can use keyStores, etc.
2. Also because it's in Java, the code is very simple and easy to understand (the networking part, anyway. The GUI stuff was generated by NetBeans so I claim no responsibility for it).
3. The SSL is optional. You can turn it off and just use it to forward plain, non-encrypted data from one TCP port on the local machine to another port on a remote machine. Sort of like that netcat-from-inetd thing that netcat's readme file talks about.
4. It has a built-in GUI that displays data from one end of the pipe in blue, the other end in black, and non-ASCII characters as hex. Use of the GUI is optional, though.

Download Source Code

There is very little documentation other than what you see above. Read the code, it's not the complicated.