RFC 2292: Advanced Sockets API for IPv6 - Defines some the advanced features of the sockets API that are required for applications to take advantage of additional features of IPv6. - http://tools.ietf.org/html/rfc2292
TCP/IP Raw Sockets - MSDN documentation about Raw Socket specification. Raw sockets can be used to create your own protocols. - http://msdn2.microsoft.com/en-us/library/ms740548.aspx
Windows Sockets 2 - Developer documentation of Winsock for all Windows platforms. - http://msdn2.microsoft.com/en-us/library/ms740673.aspx
Windows Sockets Programming - Links to get started with WinSock programming. (Ed Snible) - http://www.snible.org/winsock/
sockaddr.com - Programming Resources for WinSock 1.1 and 2 including sample programs, specifications, and links. (Lewis Napper) - http://www.sockaddr.com/
FreeBSD: Sockets - FreeBSD Developers' Handbook chapter about using sockets - http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/sockets.html
WinSock Development Information - Sample programs, technical articles, links, and an extensive WinSock error reference. (Bob Quinn) - http://www.sockets.com/