Windows Sockets Compatibility Issues
Windows Sockets 2 continues to support all of the Windows Sockets 1.1 semantics and function calls except for those dealing with pseudo-blocking. Since Windows Sockets 2 runs only in 32-bit, preemptively scheduled environments, there is no need to implement the pseudo-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 pseudo-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 code modification must occur. In most cases, the judicious use of threads can be substituted to accommodate processing that was being accomplished with a blocking hook function.