Problem with QSerialPort

[Eduardo Huerta]

My problem is the following, I have two slot functions connected to a QPushButton that make the connection and disconnect to an arduino . And in the connection function I show a message on a display that arduino is already connected to the PC and in the other function show a message on the display when I disconnect. Then I show the functions A and B, I have reviewed and the problem I have is that the signal does not send the arduino, in the case of the connection function if I do a slot function where it has only arduino -> write(code), the message is received by the arduino. And in the case of disconnection if I remove the function close () I get the message displayed on the display.
Why is the message not sent to the arduino when I send it through the slot functions A and B?

How can I correct these functions?
Thanks for help me.

A)

void Widget::connectToArduino()
{
    if(arduino_is_available){
        // open and configure the serialport
        arduino->setPortName(selectedPort);
        arduino->open(QSerialPort::WriteOnly);
        arduino->setBaudRate(QSerialPort::Baud9600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        arduino->setFlowControl(QSerialPort::NoFlowControl);
 
        arduino->write("#STAR\n");//Code to show message of connection to the pc.
 
        connectButton->setText("Disconnect");
        enableControls();
    }else{
        // give error message if not available
        QMessageBox::warning(this, "Port error", "Couldn't find the Arduino!");
    }
}

void Widget::connectToArduino()
{
    if(arduino_is_available){
        // open and configure the serialport
        arduino->setPortName(selectedPort);
        arduino->open(QSerialPort::WriteOnly);
        arduino->setBaudRate(QSerialPort::Baud9600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        arduino->setFlowControl(QSerialPort::NoFlowControl);

        arduino->write("#STAR\n");//Code to show message of connection to the pc.

        connectButton->setText("Disconnect");
        enableControls();
    }else{
        // give error message if not available
        QMessageBox::warning(this, "Port error", "Couldn't find the Arduino!");
    }
}

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B)

void Widget::disconnectFromArduino()
{
    arduino_is_available = false;
    arduino_port_name="";
    selectedPort="";
    resetDefaults();
    if(arduino->isWritable())
    {
        qDebug() << "Is writable";
        arduino->write("#STOP\n");
    }
    closePort();
    this->repaint();
}
void Widget::closePort()
{
    portList.clear();
    PortComboBox->clear();
    //delete arduino;
    arduino->close();
}

void Widget::disconnectFromArduino()
{
    arduino_is_available = false;
    arduino_port_name="";
    selectedPort="";
    resetDefaults();
    if(arduino->isWritable())
    {
        qDebug() << "Is writable";
        arduino->write("#STOP\n");
    }
    closePort();
    this->repaint();
}
void Widget::closePort()
{
    portList.clear();
    PortComboBox->clear();
    //delete arduino;
    arduino->close();
}

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