OpenVPN is a robust and highly flexible tunneling application that uses all of the encryption, authentication, and certification features of the OpenSSL library to securely tunnel IP networks over a single TCP/UDP port.
Discussion forums and project wiki can be found here:
https://forums.openvpn.net/
http://community.openvpn.net/openvpn
...UFTP also has the capability to communicate over disjoint networks separated by one or more firewalls (NAT traversal) and without full end-to-end multicast capability (multicast tunneling) through the use of a UFTP proxy server. These proxies also provide scalability by aggregating responses from a group of receivers.
Distributed reverse / forward proxy and tunneling solution for TCP.
...A single package that makes the most of each platform by tapping into their unique capabilities, combining this power with an intuitive interface, beautiful design and Haskell's excellent support for unprecedented levels of concurrency and parallelism.
It strives for the smallest source code size (< 500 lines) while delivering maximum throughput with near zero overhead.