Asynchronous Notification Using Event Objects
The WSAEventSelect and WSAEnumNetworkEvents functions are provided to accommodate applications such as daemons and services that have no user interface (and hence do not use Windows handles). The WSAEventSelect function behaves exactly like the WSAAsyncSelect function. However, instead of causing a Windows message to be sent on the occurrence of an FD_XXX network event (for example, FD_READ and FD_WRITE), an application-designated event object is set.
Also, the fact that a particular FD_XXX network event has occurred is remembered by the service provider. The application can call WSAEnumNetworkEvents to have the current contents of the network event memory copied to an application-supplied buffer and to have the network event memory automatically cleared. If needed, the application can also designate a particular event object that is cleared along with the network event memory.