QUdpSocket not emiting readyRead in a multi files project

[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?

[Christian Ehrlicher]

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

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

Then move it to somewhere else or simply create two QUdpSocket instances.