Question

I’ve started writing an ActiveX control that makes use of sockets.

Applications that use this control may or may not also use sockets.
Is it possible for my control to tell whether WSAStartup has been called?

If not, call it. A little test reveals that calling WSAStartup multiple times is tollerated.
But what happens if a different winsock version is requested? will this break other parts of the application?

Answer 1

Yes it is possible.

And here is how it’s done.

bool WinsockInitialized()
{
    SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (s == INVALID_SOCKET){
        return false;
    }

    closesocket(s);
    return true;
}

int main()
{
    //...
    if ( !WinsockInitialized() )
       // Init winsock here...

    // Carry on as normal.
    // ...         
}

But it’s not really necessary to do this. It’s quite safe to call WSAStartup at any time. It’s also safe to end each successful call to WSAStartup() with a matching call to WSACleanup().

e.g.

// socket calls here would be an error, not initialized
WSAStartup(...)
// socket calls here OK

WSAStartup(...)
// more socket calls OK

WSACleanup()
// socket calls OK

WSACleanup()

// more socket calls error, not initialized