Check Comport

quint16 serial_usb_vendor_id;
quint16 serial_usb_product_id;
QString vendor = "D:/vendor.txt";
bool chk_status_comport=true;

ui->setup

timer_A = new QTimer(this);

connect(timer_A,SIGNAL(timeout()),this,SLOT(check_usb_comport()));
timer_A->start(100);


serial = new QSerialPort(this);
connect(serial,SIGNAL(readyRead()),this,SLOT(readData()));
ui->bt_connect->click();

void MainWindow::check_usb_comport()

{

//    if(serial->isOpen())

//    {

//        serial->close();

//        ui->bt_connect->setText("Connect");

//    }

//    else

//    {

//        serial->setPortName("COM21");

//        serial->setBaudRate(QSerialPort::Baud115200);

//        serial->setDataBits(QSerialPort::Data8);

//        serial->setFlowControl(QSerialPort::NoFlowControl);

//        serial->setParity(QSerialPort::EvenParity);

//        serial->setStopBits(QSerialPort::OneStop);

//        if( serial->open(QIODevice::ReadWrite))

//        {

//            ui->bt_connect->setText("Disconnect");

//        }

//        else

//        {

//            // QMessageBox::critical(this,tr("Error"),serial->errorString());

//            QMessageBox::information(this,"Wrong com port" ,"Please check comport");

//        }

//    }

    if ( chk_status_comport == true)

    {

      bool serial_is_available = false;

      ui->btn_read_vendor_file->click();

      QString serial_uno_port_name;

      foreach (const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts())

      {

        if (serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()) {

          if ((serialPortInfo.productIdentifier() == serial_usb_product_id)

              && (serialPortInfo.vendorIdentifier() == serial_usb_vendor_id)) {

            serial_is_available = true; //    serial uno is available on this port

            serial_uno_port_name = serialPortInfo.portName();

          }

        }

      }

      if (serial_is_available)

      {

        //qDebug() << "++++++++++++++++++++++++++++++++++";

        serial->setPortName(serial_uno_port_name);

        serial->open(QSerialPort::ReadWrite);

        serial->setBaudRate(QSerialPort::Baud115200);

        serial->setDataBits(QSerialPort::Data8);

        serial->setFlowControl(QSerialPort::NoFlowControl);

        serial->setParity(QSerialPort::NoParity);

        serial->setStopBits(QSerialPort::OneStop);

        serial->setParity(QSerialPort::EvenParity);

         ui->label_status_comport->setText("Comport Connected");

      }

      else {

          qDebug() << "------------------------------------------";

        ui->label_status_comport->show();

        ui->label_status_comport->setText("Unable to Commicate with PLC");

        //QMessageBox::information(this, "Serial Port Error", "Unable to Commicate with MCU.");

        chk_status_comport = false;

      }

    }

    else {

      ui->btn_read_vendor_file->click();

      QString serial_uno_port_name;

      foreach (const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts())

      {

        //  check if the serialport has both a product identifier and a vendor identifier

        if (serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()) {

          if ((serialPortInfo.productIdentifier() == serial_usb_product_id)

              && (serialPortInfo.vendorIdentifier() == serial_usb_vendor_id)) {   //  serial_is_available = true;

            serial_uno_port_name = serialPortInfo.portName();

          }

        }

      }

      if (serial->isOpen())

      {

        serial->close();

      }

      else

      {

        serial->setPortName(serial_uno_port_name);

        serial->setBaudRate(QSerialPort::Baud115200);

        serial->setDataBits(QSerialPort::Data8);

        serial->setStopBits(QSerialPort::OneStop);

        serial->setFlowControl(QSerialPort::NoFlowControl);

        serial->setParity(QSerialPort::EvenParity);

        if ( serial->open(QIODevice::ReadWrite))

        {

          //qDebug() << "==========================";

          chk_status_comport = true;

          ui->label_status_comport->show();

          ui->label_status_comport->setText("Comport Connected");

        }

        else

        {

          ui->label_status_comport->show();

          ui->label_status_comport->setText("Unable to Commicate with PLC");

          //QMessageBox::information(this, "Serial Port Error", "Unable to Commicate with MCU.");

        }

      }

    }

}