This function has been removed in compliance with the Windows Sockets 2 specification, revision 2.2.0.
The function is not exported directly by WS2_32.DLL, and Windows Sockets 2 applications should not use this function. Windows Sockets 1.1 applications that call this function are still supported through the WINSOCK.DLL and WSOCK32.DLL.
Blocking hooks are generally used to keep a single-threaded GUI application responsive during calls to blocking functions. Instead of using blocking hooks, an application should use a separate thread (separate from the main GUI thread) for network activity.