QUdpSocket not emiting readyRead in a multi files project

[jsulm]

@febinaf To add to @JonB : please read https://en.cppreference.com/w/cpp/language/scope

[febinaf]

@JonB said in QUdpSocket not emiting readyRead in a multi files project:
ooh ok, but I'm clueless on how to create a udp object in main (so that the readyRead is connected throughout the runtime), and use the same object in adduser file for sending over udp. I'll go through the suggested solutions.

passing it as a parameter to addUser class

could you please explain a bit more on passing the object to the class, will that help me to keep the object in scope throughout the adduser file ?

addUser User;
        User.show();

I've used the above snippet, so that the window appears again after the QMessageBox is closed. Without that, the window used to close immediately after the message box is closed. I'm trying to take the user input again after the 'Save' or 'Cancel' button is clicked. Any info regarding the proper implementation of this idea would be really helpful.

really appreciate the time :)

[jsulm]

@febinaf said in QUdpSocket not emiting readyRead in a multi files project:

how to create a udp object in main

Why in main?!
Simply make it class member...

[febinaf]

@jsulm said in QUdpSocket not emiting readyRead in a multi files project:

Simply make it class member...

ok, so i need to create an object for udp and make it the class member of addUser class ... got it thanks

[febinaf]

@jsulm Hey I've added the object for udp class in the addUser class. I've also forward declared the udp class in addUser header file. But I'm getting the error that " field 'myudp' has incomplete type 'myUDP'.
Here is the changes that I've made.

//addUser.h
#ifndef ADDUSER_H
#define ADDUSER_H
#include <QMainWindow>
#include <QDialog>
#include <QString>

namespace Ui {
class addUser;
}
class myUDP; //fwd declared

class addUser : public QDialog
{
    Q_OBJECT

public:
    explicit addUser(QWidget *parent = nullptr);
    ~addUser();
    QString packetToDevice, IP, port;
    int portNum;
    myUDP myudp; //object added as member
private slots:
    void on_pushButton_2_clicked();

private:
    Ui::addUser *ui;
    QString addUserName, addNewID, addRFID, confirmBuffer, strLength;

};
#endif // ADDUSER_H

and did #include "myudp.h" in adduser.cpp .

Also, tried to create

myUDP  *myudp; //object pointer

and added, below line in addUser constructor

myudp = new myUDP(this);

and doing so removed the errors but, the socket -> bind() in myUDP constructor returns false during operation, and the readyRead is not emitted. Could you help me with what I'm missing here.

[Christian Ehrlicher]

And where did you define + implement myUDP class?
Forward declaring an object is not possible. You can use a forward-declared class only as pointer.

[febinaf]

@Christian-Ehrlicher I've defined the myUDP class in myudp.cpp and used in in the addUser.cpp file.

I did all these steps to use the myudp object as a member of the addUser class. If this is not the right thing to do, could you guide me through the steps.

[Christian Ehrlicher]

@febinaf said in QUdpSocket not emiting readyRead in a multi files project:

If this is not the right thing to do, could you guide me through the steps.

Forward declaring an object is not possible. You can use a forward-declared class only as a pointer.

I already told you whats wrong

[febinaf]

This post is deleted!

[febinaf]

@Christian-Ehrlicher
I'm really getting into object oriented programming and pardon me if I'm asking a lot of silly questions.

I'm trying to achieve what @jsulm mentioned as "Simply make it class member..." . I've created an object in the addUser.h private sections and got errors, that's the reason for trying out forward declaration.
What I'm trying to obtain is, to make the signal readyRead() to be connected throughout the runtime, and the connect () is in the constructor of myUDP class.

[Christian Ehrlicher]

@febinaf said in QUdpSocket not emiting readyRead in a multi files project:

I've created an object in the addUser.h private sections and got errors

Then please post the error messages. What you did wrong with the forward declared class was already explained...

[febinaf]

@Christian-Ehrlicher The error was that "the class name does not name a type" .. i think it was because of not including the required header files. Got that fixed now.

Right now I've created an object in private section of addUser.h and then I'm calling a method from that object in between the addUser GUI. I'm using a debug message to get status of socket ->bind(), and it returns true as the window opens the addUser gui, and the same returns false when the sendUDP method is called inside the same window.
Is this the reason for readyRead not being emitted.

[Christian Ehrlicher]

Please post a minimal, compilable exmaple to your problem - you did so many changes, posted only parts of your code so that I don't know what you are actually really compiling...

[febinaf]

@Christian-Ehrlicher Ok
an on_pushButton_clicked from my mainwindow invokes an addUser object and shows the window.

//addUser.h
#ifndef ADDUSER_H
#define ADDUSER_H
#include <QMainWindow>
#include <QDialog>
#include <QString>
#include <myudp.h>

namespace Ui {
class addUser;
}
class addUser : public QDialog
{
    Q_OBJECT
public:
    explicit addUser(QWidget *parent = nullptr);
    ~addUser();
    QString packetToDevice, IP, port;
    int portNum;

private slots:
    void on_pushButton_2_clicked();

private:
    Ui::addUser *ui;
    QString addUserName, addNewID, addRFID, confirmBuffer, strLength;
    myUDP myudp; //object added as member
};

#endif // ADDUSER_H

//addUser.cpp
#include "adduser.h"
#include "ui_adduser.h"
#include "QMessageBox"
#include "QDebug"
#include "myudp.h" //udp header

//#include "QDeadlineTimer"

addUser::addUser(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::addUser)
{
    ui->setupUi(this);
}

addUser::~addUser()
{
    delete ui;
}

void addUser::on_pushButton_2_clicked() //submit button press
{
    addUser User;
    QMessageBox mssgBox;
    addUserName = ui->lineEdit->text();
    addNewID = ui->lineEdit_2->text();
    addRFID = ui->lineEdit_3->text();
    IP = ui->lineEdit_4->text();
    port = ui->lineEdit_5->text();
    portNum = port.toInt();

    int rfidLength = addRFID.length();
    int lengthOfName = addUserName.length();
    strLength = QString::number(lengthOfName); // number to string

    if((rfidLength == 10) && (lengthOfName <11))
    {   mssgBox.setWindowTitle("Confirmation");
        mssgBox.setText("Confirm the new user details" );
     
        mssgBox.setStandardButtons(QMessageBox::Cancel | QMessageBox::Save);
        int returnValue = mssgBox.exec();


        switch(returnValue)
        {

            case QMessageBox::Save :
                {
                //packetize and send the details over UDP
             packetToDevice = "FA"+addNewID+strLength+addUserName+addRFID;
               myudp.udpSend(packetToDevice, IP, portNum); //UDP SEND Fn CALL
 User.show(); // back to the window
                break;
                }
            case QMessageBox::Cancel :
                User.show(); //back to window
                break;
            default:
                qDebug()<<"entered default state";
        }
}

    else
    {
        QMessageBox falseMssg;
        falseMssg.setWindowTitle("Error");
        falseMssg.setText("Invalid RFID/Name");
       falseMssg.setStandardButtons(QMessageBox::Close);
        falseMssg.exec();
        User.show();

    }

}

the above one is the file where myudp object is to be used to send and readyRead should be emitted whenever datagram arrives.

then the udp header and source is as follows:

//myUdp.h
#ifndef MYUDP_H
#define MYUDP_H
#include <QObject>
#include <QUdpSocket>

class myUDP : public QObject
{
    Q_OBJECT
public:
    explicit myUDP(QObject *parent = nullptr);
    void udpSend(QString, QString, int);
signals:

public slots:
    void receiveUDP();

private:
    QUdpSocket *socket2;
};

#endif // MYUDP_H

//myudp.cpp
#include "myudp.h"
#include "QUdpSocket"
#include "QDebug"
#include "adduser.h" //

myUDP::myUDP(QObject *parent)
    : QObject{parent}
{
    socket2 = new QUdpSocket(this);
    bool result = socket2->bind(QHostAddress::Any, 1234);
    qDebug()<<"bind status"<<result;
    connect(socket2, SIGNAL(readyRead()), this, SLOT(receiveUDP()));
   
void myUDP::udpSend(QString a, QString ip, int port)
{       const char *str;
        QByteArray dataToSend;
        dataToSend = a.toLatin1(); //Qstring to const char *
        str = dataToSend.data();
        int retVal = socket2 ->writeDatagram(str, QHostAddress(ip), port);
        qDebug()<< retVal; // length of the transmitted string  if successfully transmitted or -1
}

void myUDP::receiveUDP() //called when readyRead SIGNAL is emitted.
{
    while (socket2->hasPendingDatagrams())
    {
        QByteArray datagram;
        datagram.resize(socket2->pendingDatagramSize());
        QHostAddress sender;
        quint16 senderPort;

        socket2->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort );
        qDebug()<<datagram;
        qDebug()<<"IP "<<sender.toString();
 }
}

[Christian Ehrlicher]

I don't understand what you're doing - why do you try to send something to yourself? I doubt you receive data on the same socket you're currently writing it.

[J.Hilk]

@febinaf I'm reasonably sure, that writeDatagram

void myUDP::udpSend(QString a, QString ip, int port)
{       const char *str;
        QByteArray dataToSend;
        dataToSend = a.toLatin1(); //Qstring to const char *
        str = dataToSend.data();
        int retVal = socket2 ->writeDatagram(str, QHostAddress(ip), port);
        qDebug()<< retVal; // length of the transmitted string  if successfully transmitted or -1
}

is an asynchronous process. So there might be some lifetime issues...

[febinaf]

@Christian-Ehrlicher I'm writing data to IP and port entered using user input. And I've used the same socket to send and receive, as its being shown in online tutorials ..... https://www.youtube.com/watch?v=4qx4FaglSig

I've checked the above code in another project with just main function and udp class, and both reading and writing works fine using a single socket.

[febinaf]

@J-Hilk ooh ... so the writeDatagram method may be killing the object after the methods execution?

Let me try with other write methods available in the QUdpSocket class.

[Christian Ehrlicher]

@febinaf said in QUdpSocket not emiting readyRead in a multi files project:

so the writeDatagram method may be killing the object after the methods execution?

No

And I've used the same socket to send and receive, as its being shown in online tutorials ....

Yes, but in those cases the sender and receiver are different objects, not the same one!

[febinaf]

@Christian-Ehrlicher on creating 2 different object for writing and reading, the first object creation gives the bind () status as true and when the object for write method is called, the bind() status is false.

Since the bind() is in the constructor of the class, creating new objects will execute the bind() method again and again, right?