Winsock 2 is the second generation of the Winsock networking API created by Microsoft in order to allow Windows developers to add networking functionality in their applications.
Winsock 2 improves upon Winsock by adding Quality Of Service support, Protocol independence, Multicast, and a host of features which will allow a developer to program networking code more efficiently. This includes I/O completion ports for one.
The Winsock 2 API is available by making standard DLL function calls. A 3rd-party commercial library is available that allows easier access to the Winsock 2 API through a COM interface.