void CWEComm::ThreadReceive(CWEComm* pOwner)
{
    if(!SetCommMask(pOwner->m_hComm, EV_RXCHAR|EV_ERR))
        return;

    COMSTAT    statCom;
    DWORD    dwError, dwLen, dwMask;

    while(pOwner->m_bIsRece && pOwner->IsOpen())
    {
        dwMask    = 0;
        if(!WaitCommEvent(pOwner->m_hComm, &dwMask, &pOwner->m_olWait))
        {
            switch(GetLastError())
            {
            case ERROR_ACCESS_DENIED:
                {
                    pOwner->m_bIsRece        = FALSE;
                    pOwner->m_hThreadRec    = NULL;

                    SetCommMask(pOwner->m_hComm, 0);
                    ResetEvent(pOwner->m_olWait.hEvent);
                    CloseHandle(pOwner->m_hThreadRec);
                    pOwner->Close();
                }break;
            case ERROR_IO_PENDING:GetOverlappedResult(pOwner->m_hComm, &pOwner->m_olWait, &dwLen, true);break;
            }
        }

        if(dwMask & EV_ERR)
            ClearCommError(pOwner->m_hComm, &dwError, &statCom);

        if(dwMask & EV_RXCHAR)
        {
            ClearCommError(pOwner->m_hComm, &dwError, &statCom);
            if(statCom.cbInQue>0)
                ::SendMessage(pOwner->m_hNotifyWnd, pOwner->m_uMsgID, statCom.cbInQue, 0);
        }
    }
}

------解決方案--------------------

我以前做過(guò)虛擬串口的驅(qū)動(dòng)，
如果端口突然端口后驅(qū)動(dòng)程序內(nèi)還有資源沒(méi)有釋放，那么再次打開(kāi)該端口可能打不開(kāi)，提示被占用了。
如果是驅(qū)動(dòng)的問(wèn)題應(yīng)該，如果硬件也是串口的話(huà)，應(yīng)該可以解決的

------解決方案--------------------
// ClearCommError()
// CloseHandle()

------解決方案--------------------
// reset RTS
	EscapeCommFunction(m_idComDev,CLRRTS);
//  close Comm
	PurgeComm(m_idComDev,PURGE_TXABORT | PURGE_RXABORT|
						 PURGE_TXCLEAR | PURGE_RXCLEAR);
//  
	CloseHandle(m_idComDev);

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