C / C++ / MFC

// WINDOWS NT
// we must pass a security_attributes structure to the on-create call to
// all the created threads to access the serial port!
SECURITY_ATTRIBUTES sa ;
sa.nLength = sizeof(SECURITY_ATTRIBUTES) ;
sa.lpSecurityDescriptor = NULL ;        // use default descriptor
sa.bInheritHandle = true ;              // allow sub-threads to inherit handle

m_hSerialPort = CreateFile((LPCTSTR)m_csCommPortName,
                    GENERIC_READ | GENERIC_WRITE,
                    0,
                    &sa,                            // needed for inherit
                    OPEN_EXISTING,
                    0,
                    0) ;
if (m_hSerialPort != INVALID_HANDLE_VALUE)
    {
    m_bOpen = true ;
    if (!GetCommState(m_hSerialPort, &m_dcb))
        {
        error.LoadString(IDS_CAVRO_DCB) ;
        DisplayText(error) ;
        }
    else
        {
        // make sure we are using the correct settings
        m_dcb.BaudRate = CBR_9600 ;                 // 9600 baud
        m_dcb.ByteSize = 8 ;                        // 8 data bits
        m_dcb.Parity = NOPARITY ;                   // no parity
        m_dcb.fParity = false ;                     // parity checking off
        m_dcb.StopBits = ONESTOPBIT ;               // 1 stop bit
        m_dcb.fDtrControl = DTR_CONTROL_DISABLE ;   // no DTR input flow control
        m_dcb.fOutxCtsFlow = false ;                // don't monitor CTS
        m_dcb.fDsrSensitivity = false ;             // always read bytes received
        m_dcb.fTXContinueOnXoff = true ;            // don't wait for XONN / XOFF
        m_dcb.fOutX = false ;                       // No XON / XOFF control
        m_dcb.fRtsControl = RTS_CONTROL_DISABLE ;   // don't use RTS comms control
        m_dcb.fAbortOnError = false ;               // don't quit on error
        // now apply the correct comm state to the device
        if (!SetCommState(m_hSerialPort, &m_dcb))
            {
            error.LoadString(IDS_CAVRO_STATE) ;
            DisplayText(error) ;
            }
        // set the communication event flags
        if (!SetCommMask(m_hSerialPort, EV_RXCHAR))
            {
            error.LoadString(IDS_CAVRO_MASK) ;
            DisplayText(error) ;
            }
        COMMTIMEOUTS    timeouts ;

        // return immediately on reads
        // return after completion on writes
        timeouts.ReadIntervalTimeout = MAXDWORD ;
        timeouts.ReadTotalTimeoutConstant = 0 ;
        timeouts.ReadTotalTimeoutMultiplier = 0 ;
        timeouts.WriteTotalTimeoutConstant = 0 ;
        timeouts.WriteTotalTimeoutMultiplier = 0 ;

        SetCommTimeouts(m_hSerialPort, &timeouts) ;
        }
    }