C++ Redefinition Header Files (winsock2.h)

This problem is caused when including <windows.h> before <winsock2.h>. Try arrange your include list that <windows.h> is included after <winsock2.h> or define _WINSOCKAPI_ first:

#define _WINSOCKAPI_    // stops windows.h including winsock.h
#include <windows.h>
// ...
#include "MyClass.h"    // Which includes <winsock2.h>

See also this.