A Unix Utility You Should Know About: Netcat - good coders code, great reuse
Useful Uses Of netcat | HowtoForge - Linux Howtos and Tutorials
This short article shows some useful netcat commands. netcat is known as the TCP/IP swiss army knife. From the netcat man page: netcat is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. It is designed to be a reliable "back-end" tool that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and exploration tool, since it can create almost any kind of connection you would need and has several interesting built-in capabilities.