It works by being a client of a supposedly open name server and updating the server´s records when the need arise. The servers that are supported are http://www.dyndns.org, http://freedns.afraid.org, http://www.zoneedit.com http://www.no-ip.com.

Some of the services of these servers are free of charge.

This is a command line tool that is written in portable ANSI C with a little OS abstraction layer. It can maintain multiple host names with the same IP address, and has a web based IP detection which runs well behind a NAT router.