DWORD dwBytesWritten = 0;
  BOOL bSuccess = WriteFile(m_hComm, lpBuf, dwCount, &dwBytesWritten, &overlapped);
  if (!bSuccess)
  {
    if (GetLastError() != ERROR_IO_PENDING)
    {
      TRACE(_T("CSerialPort::Write, Failed in call to WriteFile\n"));
      ThrowSerialException();
    }
  }
  else
  {
    if (pBytesWritten)
      *pBytesWritten = dwBytesWritten;
  }

  return bSuccess;
}

void CSerialPort::GetOverlappedResult(OVERLAPPED& overlapped, DWORD& dwBytesTransferred, BOOL bWait)
{
  ASSERT(IsOpen());

  if (!::GetOverlappedResult(m_hComm, &overlapped, &dwBytesTransferred, bWait))
  {
    if (GetLastError() != ERROR_IO_INCOMPLETE)
    {
      TRACE(_T("CSerialPort::GetOverlappedResult, Failed in call to GetOverlappedResult\n"));
      ThrowSerialException();
    }
  }
}

void CSerialPort::_OnCompletion(DWORD dwErrorCode, DWORD dwCount, LPOVERLAPPED lpOverlapped)
{
  //Validate our parameters
  ASSERT(lpOverlapped);

  //Convert back to the C++ world
  CSerialPort* pSerialPort = static_cast<CSerialPort*>(lpOverlapped->hEvent);
  ASSERT(pSerialPort);

  //Call the C++ function
  pSerialPort->OnCompletion(dwErrorCode, dwCount, lpOverlapped);
}

void CSerialPort::OnCompletion(DWORD /*dwErrorCode*/, DWORD /*dwCount*/, LPOVERLAPPED lpOverlapped)
{
  //Just free the memory which was previously allocated for the OVERLAPPED structure
	try
	{
		delete lpOverlapped;
	}
	catch (...)
	{
		
	}
  

  //Your derived classes can do something useful in OnCompletion, but don't forget to
  //call CSerialPort::OnCompletion to ensure the memory is freed
}

void CSerialPort::CancelIo()
{
  ASSERT(IsOpen());

  if (m_lpfnCancelIo == NULL)
  {
    TRACE(_T("CSerialPort::CancelIo, CancelIo function is not supported on this OS. You need to be running at least NT 4 or Win 98 to use this function\n"));
    ThrowSerialException(ERROR_CALL_NOT_IMPLEMENTED);  
  }

  if (!m_lpfnCancelIo(m_hComm))
  {
    TRACE(_T("Failed in call to CancelIO\n"));
    ThrowSerialException();
  }
}

DWORD CSerialPort::BytesWaiting()
{
  ASSERT(IsOpen());

  //Check to see how many characters are unread
  COMSTAT stat;
  GetStatus(stat);
  return stat.cbInQue;
}

BOOL CSerialPort::DataWaiting(DWORD dwTimeout)
{
  ASSERT(IsOpen());

  //Setup to wait for incoming data
  DWORD dwOldMask;
  GetMask(dwOldMask);
  SetMask(EV_RXCHAR);

  //Setup the overlapped structure
  OVERLAPPED o;
  o.hEvent = m_hEvent;

  //Assume the worst;
  BOOL bSuccess = FALSE;

  DWORD dwEvent;
  bSuccess = WaitEvent(dwEvent, o);
  if (!bSuccess)
  {
    if (WaitForSingleObject(o.hEvent, dwTimeout) == WAIT_OBJECT_0)
    {
      DWORD dwBytesTransferred;
      GetOverlappedResult(o, dwBytesTransferred, FALSE);
      bSuccess = TRUE;
    }
  }

  //Reset the event mask
  SetMask(dwOldMask);

  return bSuccess;
}

void CSerialPort::WriteEx(const void* lpBuf, DWORD dwCount)
{
  ASSERT(IsOpen());

  OVERLAPPED* pOverlapped = new OVERLAPPED;
  ZeroMemory(pOverlapped, sizeof(OVERLAPPED));
  pOverlapped->hEvent = static_cast<HANDLE>(this);
  if (!WriteFileEx(m_hComm, lpBuf, dwCount, pOverlapped, _OnCompletion))
  {
    delete pOverlapped;
    TRACE(_T("CSerialPort::WriteEx, Failed in call to WriteFileEx\n"));
    ThrowSerialException();
  }
}


void CSerialPort::ReadEx(void* lpBuf, DWORD dwCount)
{
  ASSERT(IsOpen());

  OVERLAPPED* pOverlapped = new OVERLAPPED;
  ZeroMemory(pOverlapped, sizeof(OVERLAPPED));
  pOverlapped->hEvent = static_cast<HANDLE>(this);
  if (!ReadFileEx(m_hComm, lpBuf, dwCount, pOverlapped, _OnCompletion))
  {
    delete pOverlapped;
    TRACE(_T("CSerialPort::ReadEx, Failed in call to ReadFileEx\n"));
    ThrowSerialException();
  }
}

void CSerialPort::TransmitChar(char cChar)
{
  ASSERT(IsOpen());

  if (!TransmitCommChar(m_hComm, cChar))
  {
    TRACE(_T("CSerialPort::TransmitChar, Failed in call to TransmitCommChar\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetConfig(COMMCONFIG& config)
{
  ASSERT(IsOpen());

  DWORD dwSize = sizeof(COMMCONFIG);
  if (!GetCommConfig(m_hComm, &config, &dwSize))
  {
    TRACE(_T("CSerialPort::GetConfig, Failed in call to GetCommConfig\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetConfig(COMMCONFIG& config)
{
  ASSERT(IsOpen());

  DWORD dwSize = sizeof(COMMCONFIG);
  if (!SetCommConfig(m_hComm, &config, dwSize))
  {
    TRACE(_T("CSerialPort::SetConfig, Failed in call to SetCommConfig\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetBreak()
{
  ASSERT(IsOpen());

  if (!SetCommBreak(m_hComm))
  {
    TRACE(_T("CSerialPort::SetBreak, Failed in call to SetCommBreak\n"));
    ThrowSerialException();
  }
}

void CSerialPort::ClearBreak()
{
  ASSERT(IsOpen());

  if (!ClearCommBreak(m_hComm))
  {
    TRACE(_T("CSerialPort::ClearBreak, Failed in call to SetCommBreak\n"));
    ThrowSerialException();
  }
}

void CSerialPort::ClearError(DWORD& dwErrors)
{
  ASSERT(IsOpen());

  if (!ClearCommError(m_hComm, &dwErrors, NULL))
  {
    TRACE(_T("CSerialPort::ClearError, Failed in call to ClearCommError\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetDefaultConfig(int nPort, COMMCONFIG& config)
{
  //Validate our parameters
  ASSERT(nPort>0 && nPort<=255);

  //Create the device name as a string
  CString sPort;
  sPort.Format(_T("COM%d"), nPort);

  DWORD dwSize = sizeof(COMMCONFIG);
  if (!GetDefaultCommConfig(sPort, &config, &dwSize))
  {
    TRACE(_T("CSerialPort::GetDefaultConfig, Failed in call to GetDefaultCommConfig\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetDefaultConfig(int nPort, COMMCONFIG& config)
{
  //Validate our parameters
  ASSERT(nPort>0 && nPort<=255);

  //Create the device name as a string
  CString sPort;
  sPort.Format(_T("COM%d"), nPort);

  DWORD dwSize = sizeof(COMMCONFIG);
  if (!SetDefaultCommConfig(sPort, &config, dwSize))
  {
    TRACE(_T("CSerialPort::SetDefaultConfig, Failed in call to SetDefaultCommConfig\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetStatus(COMSTAT& stat)
{
  ASSERT(IsOpen());

  DWORD dwErrors;
  if (!ClearCommError(m_hComm, &dwErrors, &stat))
  {
    TRACE(_T("CSerialPort::GetStatus, Failed in call to ClearCommError\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetState(DCB& dcb)
{
  ASSERT(IsOpen());

  if (!GetCommState(m_hComm, &dcb))
  {
    TRACE(_T("CSerialPort::GetState, Failed in call to GetCommState\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetState(DCB& dcb)
{
  ASSERT(IsOpen());

  if (!SetCommState(m_hComm, &dcb))
  {
    TRACE(_T("CSerialPort::SetState, Failed in call to SetCommState\n"));
    ThrowSerialException();
  }
}

void CSerialPort::Escape(DWORD dwFunc)
{
  ASSERT(IsOpen());

  if (!EscapeCommFunction(m_hComm, dwFunc))
  {
    TRACE(_T("CSerialPort::Escape, Failed in call to EscapeCommFunction\n"));
    ThrowSerialException();
  }
}

void CSerialPort::ClearDTR()
{
  Escape(CLRDTR);
}

void CSerialPort::ClearRTS()
{
  Escape(CLRRTS);
}

void CSerialPort::SetDTR()
{
  Escape(SETDTR);
}

void CSerialPort::SetRTS()
{
  Escape(SETRTS);
}

void CSerialPort::SetXOFF()
{
  Escape(SETXOFF);
}

void CSerialPort::SetXON()
{
  Escape(SETXON);
}

void CSerialPort::GetProperties(COMMPROP& properties)
{
  ASSERT(IsOpen());

  if (!GetCommProperties(m_hComm, &properties))
  {
    TRACE(_T("CSerialPort::GetProperties, Failed in call to GetCommProperties\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetModemStatus(DWORD& dwModemStatus)
{
  ASSERT(IsOpen());

  if (!GetCommModemStatus(m_hComm, &dwModemStatus))
  {
    TRACE(_T("CSerialPort::GetModemStatus, Failed in call to GetCommModemStatus\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetMask(DWORD dwMask)
{
  ASSERT(IsOpen());

  if (!SetCommMask(m_hComm, dwMask))
  {
    TRACE(_T("CSerialPort::SetMask, Failed in call to SetCommMask\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetMask(DWORD& dwMask)
{
  ASSERT(IsOpen());

  if (!GetCommMask(m_hComm, &dwMask))
  {
    TRACE(_T("CSerialPort::GetMask, Failed in call to GetCommMask\n"));
    ThrowSerialException();
  }
}

void CSerialPort::Flush()
{
  ASSERT(IsOpen());

  if (!FlushFileBuffers(m_hComm))
  {
    TRACE(_T("CSerialPort::Flush, Failed in call to FlushFileBuffers\n"));
    ThrowSerialException();
  }
}

void CSerialPort::Purge(DWORD dwFlags)
{
  ASSERT(IsOpen());

  if (!PurgeComm(m_hComm, dwFlags))
  {
    TRACE(_T("CSerialPort::Purge, Failed in call to PurgeComm\n"));
    ThrowSerialException();
  }
}

void CSerialPort::TerminateOutstandingWrites()
{
  Purge(PURGE_TXABORT);
}

void CSerialPort::TerminateOutstandingReads()
{
  Purge(PURGE_RXABORT);
}

void CSerialPort::ClearWriteBuffer()
{
  Purge(PURGE_TXCLEAR);
}

void CSerialPort::ClearReadBuffer()
{
  Purge(PURGE_RXCLEAR);
}

void CSerialPort::Setup(DWORD dwInQueue, DWORD dwOutQueue)
{
  ASSERT(IsOpen());

  if (!SetupComm(m_hComm, dwInQueue, dwOutQueue))
  {
    TRACE(_T("CSerialPort::Setup, Failed in call to SetupComm\n"));
    ThrowSerialException();
  }
}

void CSerialPort::SetTimeouts(COMMTIMEOUTS& timeouts)
{
  ASSERT(IsOpen());

  if (!SetCommTimeouts(m_hComm, &timeouts))
  {
    TRACE(_T("CSerialPort::SetTimeouts, Failed in call to SetCommTimeouts\n"));
    ThrowSerialException();
  }
}

void CSerialPort::GetTimeouts(COMMTIMEOUTS& timeouts)
{
  ASSERT(IsOpen());

  if (!GetCommTimeouts(m_hComm, &timeouts))
  {
    TRACE(_T("CSerialPort::GetTimeouts, Failed in call to GetCommTimeouts\n"));
    ThrowSerialException();
  }
}

void CSerialPort::Set0Timeout()
{
  COMMTIMEOUTS Timeouts;
  ZeroMemory(&Timeouts, sizeof(COMMTIMEOUTS));
  Timeouts.ReadIntervalTimeout = MAXDWORD;
  SetTimeouts(Timeouts);
}

void CSerialPort::Set0WriteTimeout()
{
  COMMTIMEOUTS Timeouts;
  GetTimeouts(Timeouts);
  Timeouts.WriteTotalTimeoutMultiplier = 0;
  Timeouts.WriteTotalTimeoutConstant = 0;
  SetTimeouts(Timeouts);
}

void CSerialPort::Set0ReadTimeout()
{
  COMMTIMEOUTS Timeouts;
  GetTimeouts(Timeouts);
  Timeouts.ReadIntervalTimeout = MAXDWORD;
  Timeouts.ReadTotalTimeoutMultiplier = 0;
  Timeouts.ReadTotalTimeoutConstant = 0;
  SetTimeouts(Timeouts);
}

void CSerialPort::WaitEvent(DWORD& dwMask)
{
  ASSERT(IsOpen());

  if (!WaitCommEvent(m_hComm, &dwMask, NULL))
  {
    TRACE(_T("CSerialPort::WaitEvent, Failed in call to WaitCommEvent\n"));
    ThrowSerialException();
  }
}

BOOL CSerialPort::WaitEvent(DWORD& dwMask, OVERLAPPED& overlapped)
{
  ASSERT(IsOpen());
  ASSERT(overlapped.hEvent);

  BOOL bSuccess = WaitCommEvent(m_hComm, &dwMask, &overlapped);
  if (!bSuccess)
  {
    if (GetLastError() != ERROR_IO_PENDING)
    {
      TRACE(_T("CSerialPort::WaitEvent, Failed in call to WaitCommEvent\n"));
      ThrowSerialException();
    }
  }

  return bSuccess;
}