netcat6 is an IPv6-enabled clone of the original netcat utility.

"Netcat is a simple Unix utility which reads and writes data across
network connections. 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. Netcat,
or "nc" as the actual program is named, should have been supplied long
ago as another one of those cryptic but standard Unix tools."