slackbuilds/network/netcat

GNU Netcat is a featured networking utility which reads and writes
data across network connections, using the TCP/IP 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.