Windows Sockets 2 continues to support all of the Windows Sockets 1.1 semantics and function calls except for those dealing with psuedo-blocking. Since Windows Sockets 2 runs only in 32-bit, pre-emptively scheduled environments such as Windows NT and Windows 95, there is no need to implement the psuedo-blocking found in Windows Sockets 1.1. This means that the WSAEINPROGRESS error code will never be indicated and that the following Windows Sockets 1.1 functions are not available to Windows Sockets 2 applications:
Windows Sockets 1.1 programs that are written to utilize psuedo-blocking will continue to operate correctly since they link to either WINSOCK.DLL or WSOCK32.DLL. Both continue to support the complete set of Windows Sockets 1.1 functions. In order for programs to become Windows Sockets 2 applications, some amount of code modification must occur. In most cases, you will substitute the judicious use of threads to accommodate processing that was being accomplished with a blocking hook function.