Default State for a Socket's Overlapped Attribute
The socket function created sockets with the overlapped attribute set by default in the first Wsock32.dll, the 32-bit version of Windows Sockets 1.1. In order to ensure backward compatibility with currently deployed Wsock32.dll implementations, this will continue to be the case for Windows Sockets 2 as well. That is, in Windows Sockets 2 sockets created with the socket function will have the overlapped attribute. However, in order to be more compatible with the rest of the Windows API, sockets created with WSASocket will not, default, have the overlapped attribute. This attribute will only be applied if the WSA_FLAG_OVERLAPPED bit is set.