CSTCPProxy is a single threaded, single process (non-forking) daemon that is used to proxy TCP connections. It will listen on any ip:port and connect to and proxy everything to a different ip:port. The outgoing connections can be configured (individually) to come from any interface of your machine. You can also individually configure which IPs are allowed to connect, as of version 1.3.
The latest version of CSTCPProxy is cstcpproxy-1.4.tar.gz. The README contains information on how to use, and config file format, etc. The ChangeLog details the changes between versions.