How to make QT automatically connect to correct COM Port

[GunkutA]

I am trying to make QT automatically connect to my ST32 MCU by serial. MCU is keep sending data for each second. So I thought I can read all the available COM Ports and when the line is not null, I will detect that COM Port is MCU. But All COM Ports are null. Here is related piece of code I am using in QT:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtSerialPort>
#include <QDebug>
QSerialPort *serial;
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    serial = new QSerialPort(this);
    foreach(QSerialPortInfo port, QSerialPortInfo::availablePorts())
    {
            serial->setPortName(port.portName());
            serial->setBaudRate(QSerialPort::Baud115200);
            serial->setDataBits(QSerialPort::Data8);
            serial->setParity(QSerialPort::NoParity);
            serial->setStopBits(QSerialPort::OneStop);
            serial->setFlowControl(QSerialPort::NoFlowControl);
            serial->open(QIODevice::ReadOnly);
 
            if(!(serial->readLine().isNull()))
            {
                qDebug()<<port.portName()<<"is opened";
            }
 
    }
}

I believe 1 second is not enough for QT to detect that. Maybe I should use timeout in QT. Any idea how can I solve this problem?

[J.Hilk]

@GunkutA
point 1: you have no checks what so ever if the opening succeeds
point 2: There is no guarantee that your serialport instance already received data after opening, in fact it's near impossible.

point 3: PLEASE use the asynchronous api of QSerialPort with readyRead & bytesWritten Signals etc.

[GunkutA]

@J-Hilk Thank you for your feedback. To make things more clear:

1. I checked and all ports are connected successfully.
2. My MCU is trying to send data for every 1 second, so maybe I should check it with a Signal and Slot. But in this case how I will test it with all COM Ports and find the correct one?
3. I don't know what is "asynchronous api of QSerialPort with readyRead & bytesWritten Signals etc.". I am newbie to QT and C++...

[jsulm]

@GunkutA said in How to make QT automatically connect to correct COM Port:

I don't know what is "asynchronous api of QSerialPort with readyRead & bytesWritten Signals etc."

Then please read documentation:
https://doc.qt.io/qt-5/qserialport.html
https://doc.qt.io/qt-5/qiodevice.html#readyRead
https://doc.qt.io/qt-5/qiodevice.html#bytesWritten

Qt is an asynchronous framework and should be used as such.