shutdown workerthread (Readfile hangs)

Hi,

I`ve installed a worker thread for a serial port. It is already
working as expected - but I`m not able to shutdown this worker thread
if the thread hangs in the Readfile() command (because no further data
will be received)....

How can I abort the Readfile command so that I can handle the shutdown
event?

/* static */
UINT CDmxReaderThread::ReaderThread(LPVOID p)
{
    CDmxSerialParameters * parms = (CDmxSerialParameters *)p;
    OVERLAPPED ovl = {0};
    ovl.hEvent = ::CreateEvent(NULL, TRUE, FALSE, NULL);
    if(ovl.hEvent == NULL)
      { /* failed */
       DWORD err = ::GetLastError();
   // parms->notifyee->PostMessage(UWM_READER_SHUTTING_DOWN,
(WPARAM)err);
       return 0;
      } /* failed */

    DWORD shutdown; // reason for shutdown
    HANDLE waiters[2];
    waiters[0] = parms->shutdown;
    waiters[1] = ovl.hEvent;

#define MAX_BUFFER_SIZE 513
    BOOL running = TRUE;
    DWORD bytesRead;
    while(running)
    { /* read loop */
        BYTE buffer[MAX_BUFFER_SIZE];
        BOOL ok = ::ReadFile(parms->hCom, buffer, MAX_BUFFER_SIZE - 1,
&bytesRead, &ovl);
        if(!ok)
       {
           //waitformultiple-events to handle shutdown
       }
}

best regards
Hans