UINT __cdecl OnWatchCom(LPVOID lparam)

{

	CBillDlg *pDlg = (CBillDlg *)lparam;

	if(pDlg == NULL) return -1;

	CString strResult;

	char buff[128] = {0};

	while(pDlg->m_IsWatching)

	{

		if(pDlg->m_Com.ReadCom(buff,128,2000))

		{

			pDlg->m_Com.ClearComBuf(PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);

			strResult.Format(_T("%s"),buff);

			if(!strResult.IsEmpty())

			{

				pDlg->m_strBillNo = strResult;

				pDlg->UpdateData(0);		

			}

		}

		Sleep(50);

	}

	return 0;

}

BOOL CComport::ReadCom(char *buff, int nlen, int dwMiniTimeout)

{

	if(!IsOpen()) return FALSE;

	OVERLAPPED m_osRead;

	memset(&m_osRead,0,sizeof(OVERLAPPED));

	m_osRead.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);



	COMSTAT ComStat;

	DWORD dwErrorFlags;

	

	memset(buff,'\0',nlen);

	DWORD dwBytesRead=nlen;//读取的字节数

	BOOL bReadStat;



	ClearComErr(&dwErrorFlags,&ComStat);

	dwBytesRead=min(dwBytesRead, (DWORD)ComStat.cbInQue);

	bReadStat=ReadFile(m_hCom,buff,dwBytesRead,&dwBytesRead,&m_osRead);

	if(!bReadStat)

	{

		if(GetLastError()==ERROR_IO_PENDING)//GetLastError()函数返回ERROR_IO_PENDING,表明串口正在进行读操作

		{

			//GetOverlappedResult(m_hCom,&m_osRead,&dwBytesRead,TRUE);

			WaitForSingleObject(m_osRead.hEvent,dwMiniTimeout);

		    //使用WaitForSingleObject函数等待，直到读操作完成或延时已达到2秒钟

		    //当串口读操作进行完毕后，m_osRead的hEvent事件会变为有信号

			//ResetEvent(m_osRead.hEvent);

		}

	}

	CloseHandle(m_osRead.hEvent);

	return TRUE;

}