Netcat is a simple Unix utility that reads and writes data across network connections, using TCP or UDP protocols. 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 may need and has several interesting built-in capabilities.
You can find the documentation in /opt/freeware/share/doc/packages/netcat/README.
Current version: v1.10-2