QUpdSocket The program has unexpectedly finished.

Hello,
VirtualBox, openSUSE13.1, Qt Creator 2.8 Qt4.8
I want to receive data to other machine to my application but now I want to check and I have a application to write a message and another to read messages, but the application to write unexpectedly finished.

In the .h:

QUdpSocket *udpSocket;
QTimer *timer;


Application to read

Code:

---

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QUdpSocket>
#include <QByteArray>
#include <string.h>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    initSocket();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::initSocket()
 {
     udpSocket = new QUdpSocket(this);
     udpSocket->bind(QHostAddress::LocalHost, 7755);
 
     connect(udpSocket, SIGNAL(readyRead()),this, SLOT(readPendingDatagrams()));
     emit SIGNAL(readyRead());
 }
 
 void MainWindow::readPendingDatagrams()
 {
     while (udpSocket->hasPendingDatagrams()) {
         QByteArray datagram;
         datagram.resize(udpSocket->pendingDatagramSize());
         QHostAddress sender;
         quint16 senderPort;
 
         udpSocket->readDatagram(datagram.data(), datagram.size(),&sender, &senderPort);
         processTheDatagram(datagram);
     }
 }
 
 
 void MainWindow::processTheDatagram(QByteArray datagram)
 {
     QDataStream in(&datagram, QIODevice::ReadOnly);
 
     for(int i=0;i<datagram.size();i++){
         //ui->label_2->setText(datagram.at(i).toString());      
         ui->label_2->setText("Recibido");
     }
 }

---

Application to write

Code:

---

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    initSocket();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::initSocket()
 {
     udpSocket = new QUdpSocket(this);
     udpSocket->bind(QHostAddress::LocalHost, 7755);
 
     connect(timer, SIGNAL(timeout()), this, SLOT(sendDatagram()));
     timer->start(2*1000);
 }
 
void MainWindow::sendDatagram()
{
    QByteArray datagram_send;
 
    datagram_send.append("Mensaje 1");
    udpSocket->writeDatagram(datagram_send.data(),datagram_send.size(),QHostAddress::LocalHost, 7755);
}

---

Maybe to check I don't need another application to check and only a method to write and call it when I initialize the QUpdSocket.
Any idea?? thanks

Where does the writing application instantiate the QTimer that it used in initSocket()?

Cheers,
_

header to write

Code:

---

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QUdpSocket>
#include <QByteArray>
#include <QTimer>
 
namespace Ui {
class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    void initSocket();
 
public slots:
    void sendDatagram();
 
private:
    Ui::MainWindow *ui;
    QUdpSocket *udpSocket;
    QTimer *timer;
};
 
#endif // MAINWINDOW_H

---

header to read

Code:

---

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QUdpSocket>
#include <QByteArray>
#include <QTimer>
 
namespace Ui {
class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    void initSocket();
 
public slots:
    void sendDatagram();
 
private:
    Ui::MainWindow *ui;
    QUdpSocket *udpSocket;
    QTimer *timer;
};
 
#endif // MAINWINDOW_H

---

thanks,

nice, but that does not answer the question.
Again: where do you create the QTimer instance?

Cheers,
_

That's all! :confused:

What I was trying to hit at is that you need to create an instance of QTimer if you want to use it :)
Right now you are using an uninitialized pointer.

Cheers,
_

Thanks!!!! I can send and receive!!! :)


Now I have the next problem, but why I can't do this?

Code:

---

ui->label_2->setText(datagram.at(i).toString());

---

Build:
Request for member 'toString' in 'datagram.QByteArray::at(i), which is of non-class type char
ui->label_2->setText(datagram.at(i).toString());

Thanks another time!!

QByteArray::at() returns a char, a single character. It is not a class and does not have any methods.

If you want to display the string inside the byte array, use one of the QString::fromXYZ methods, e.g. QString::fromAscii()

Cheers,
_

Ok, thanks!!!