rinetd

Internet TCP redirection server

rinetd redirects TCP connections from one IP address and port to another, with basic IP-based access control. rinetd is a single-process server which handles any number of connections to the address/port pairs specified in the file /etc/rinetd.conf. Since rinetd runs as a single process using nonblocking I/O, it is able to redirect a large number of connections without a severe impact on the machine. This makes it practical to run services on machines inside an IP masquerading firewall.