C / C++ / MFC

#define READ_TIMEOUT	500 // Milliseconds

UINT CPageOneDialog::monitorPTZThread(LPVOID pParam)
{
	DWORD		dwRead, dwRes;
	BOOL		fWaitingOnRead = FALSE;
	OVERLAPPED	osReader = {0};
	char ptzControlCommPort[14];
	struct PTZCommStruct *pPTZStruct = (struct PTZCommStruct *)pParam;


	// Open the comm port.
	sprintf(ptzControlCommPort,"\\\\.\\COM%d",PTZCTRLPORT+1);
	pPTZStruct->hPTZSerial = CreateFile( ptzControlCommPort,
				  GENERIC_READ | GENERIC_WRITE,
				  0,    // must be opened with exclusive-access
				  NULL, // no security attributes
				  OPEN_EXISTING, // must use OPEN_EXISTING
				  FILE_FLAG_OVERLAPPED,    // overlapped I/O
				  NULL  // hTemplate must be NULL for comm devices
				  );
	
	
	// Create the overlapped event.
	osReader.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

	if(osReader.hEvent == NULL)
	{
		// Error creatiing overlapped event, abort.
		pPTZStruct->pWnd->PostMessage(UWM_READER_SHUTTING_DOWN);
		return 0;
	} 

	while(pPTZStruct->nPTZCommTerminate == 0)
	{
		if(!fWaitingOnRead)
		{
			// Issue read Operation.
			if(!ReadFile(pPTZStruct->hPTZSerial,PTZbuffer, MAX_BUFFER_SIZE, &dwRead, &osReader))
			{
				if(GetLastError() != ERROR_IO_PENDING) // read not delayed
				{
					// Error in comms - report!!!
					return 0;
				}
				else
				{
					fWaitingOnRead = TRUE;
				}
			}
			else
			{
				// ***Read the data
			}
		}
		else
		{
			dwRes = WaitForSingleObject(osReader.hEvent, READ_TIMEOUT);
			switch(dwRes)
			{
				// Read Completed
			case WAIT_OBJECT_0:
				if(!GetOverlappedResult(pPTZStruct->hPTZSerial, &osReader, &dwRead, FALSE))
				{
					DWORD dwError = GetLastError();
					switch(dwError)
					{
						case ERROR_HANDLE_EOF:
							return 0;
							break;
						case ERROR_IO_PENDING:
							return 0;
							break;
						case ERROR_IO_INCOMPLETE:
							return 0;
							break;
						case ERROR_OPERATION_ABORTED:
							return 0;
							break;
						default:
							// error in comms - report
							Dump1("Serial Read Error %d\r\n", ::GetLastError());
							return 0;
							break;
					}
				}
				else
				{
					// ***Read the Data 
				}
				fWaitingOnRead = FALSE;
				break;

			case WAIT_TIMEOUT:
				// Operation isn't complete yet. 				
break;

			default:
				// Error in the WaitForSigleObject; abort!!!!

				return 0;
				break;

			}
		}
	}
	return 0;
}