It ships with a version of netcat that supports IPv6, as explained in the man page.
The -6
option should force nc to use IPv6 only.
To test this, I use the en0 adapter on my Mac, which has an IPv4 address of 192.168.5.142 and an IPv6 address of 2::1.
I opened a listening port on the Mac with the -6 option. But netstat shows it listening on "tcp46" rather than "tcp6".
I scanned it from a Backtrack virtual machine. It really is listening on both IPv4 and IPv6. How rude!