In TCP/IP Illustrated Vol. 1, Richard Stevens used a program called
"sock" to demonstrate the many properties of TCP/IP.  This is a
standalone version, adapted and reworked by Christian Kreibich.

The program can be used to generate TCP or UDP packets for testing
various network features.  It runs as either client or server.

This FreeBSD port is built on top of the original 0.3.2 tarball from
2010, above, downloaded from the icir.org webpage.

Version 0.4.2 of sock supports IPv6, SCTP and those socket options:
- IPv6:
  o hop limit
  o multicast hop limit
  o disable/enable header flow label
  o header traffic class
  o don't fragment
- IPv4:
  o don't fragment