SOCKS Server and Library for Java. Support for versions 4 and 5 of SOCKS protocol. Designed to be easily expandable to support different encryption/authentication/authorization methods. Sample server and client are available.
A Simple Middlebox Configuration Protocol (RFC 4540) implementation for Linux.
SIMCO is a signaling protocol that can be used by applications (such as SIP B2BUAs) to dynamically control firewalls and Network Address Translators (NATs).