Problem with QSerialPort

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)

Code:

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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)

Code:

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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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Quote:

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Originally Posted by Eduardo Huerta

My problem is the following, I have two slot functions connected to a QPushButton

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You are aware that both slots will be called for each click, right?

Quote:

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Originally Posted by Eduardo Huerta

Why is the message not sent to the arduino when I send it through the slot functions A and B?

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Maybe closing the port aborts sending any bytes that have not been sent yet.
I.e. if write() is not synchronous the stop message might still be on the PC side and close might simply discard it.

Cheers,
_