use Win32::API::Prototype;

ApiLink( 'Kernel32', q[
    HANDLE CreateIoCompletionPort(
      HANDLE FileHandle,
      HANDLE ExistingCompletionPort,
      ULONG_PTR CompletionKey,
      DWORD NumberOfConcurrentThreads
    )] 
);

my $hIOCP = CreateIoCompletionPort( $hSocket, 0, 0, 0 );