Send Custom class object using QtcpSocket and QtcpServer

[Anmol]

i am creating a network system. i know how to send text over network but i need to send my Custom class object over network. how can i send a object over TCP network.

[Christian Ehrlicher]

You need to serialize your class and deserialize it on the other side. You can use QDataStream for this or write it by your own.

[Anmol]

@Christian-Ehrlicher

deserialize not working. after deserialize getName() [ myserver.cpp -- readredy() ] returns empty string

my entire test project : https://github.com/Anmol-A-jain/test.git

i'm trying to send Data class over network.
data.h

#ifndef DATA_H
#define DATA_H

#include <QtCore>

class Data
{
public:
    Data();
    void setName(QString name);
    QString getName();
private:
    QString Name;
};

#endif // DATA_H

data.cpp

#include "data.h"

Data::Data()
{
    this->Name = "null";
}

void Data::setName(QString name)
{
    this->Name = name;
}

QString Data::getName()
{
    return this->Name;
}

client:
main.cpp

#include <QCoreApplication>
#include <QTcpSocket>
#include <QDataStream>
#include <QDebug>
#include "data.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QTcpSocket* client = new QTcpSocket;

    client->connectToHost("127.0.0.1", 5555);

    Data d;
    d.setName("Anmol");

    QByteArray byte;
    qDebug() << "d String :" << d.getName();
    QDataStream data(&byte,QIODevice::WriteOnly);
    data.writeRawData(reinterpret_cast<const char*>(&d),sizeof(d));

    qDebug() << byte;

    client->write(byte);

    return a.exec();
}

server :
myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>
#include <QDebug>

class myServer : public QObject
{
    Q_OBJECT
private:
    QTcpServer* server;

public:
    explicit myServer(QObject *parent = nullptr);

signals:

public slots:
    void newConnection();
    void readredy();
};

#endif // MYSERVER_H

myserver.cpp

#include "myserver.h"
#include "data.h"

myServer::myServer(QObject *parent) : QObject(parent)
{
    server = new QTcpServer();
    clientList = new QVector<QTcpSocket*>();

    connect(server,SIGNAL(newConnection()),this,SLOT(newConnection()));

    if(server->listen(QHostAddress::Any,5555) )
    {
        qDebug() << "connection started" << endl;
    }
    else
    {
        qDebug() << "connection not started" << endl;
    }
}

void myServer::newConnection()
{
    QTcpSocket *client = server->nextPendingConnection();
    connect(client,&QTcpSocket::readyRead,this,&myServer::readredy );
}

void myServer::readredy()
{
    QTcpSocket *client = static_cast<QTcpSocket *>(QObject::sender());
    QByteArray byte = client->readAll();

    QDataStream read(&byte,QIODevice::ReadOnly);
    Data d1 ;
    qDebug() << "d1 String before deserialize :" << d1.getName();

    read.readRawData(reinterpret_cast<char*>(&d1),sizeof(d1));
    qDebug() << "d1 String after deserialize :" << d1.getName();

    qDebug() << "Message: " + d1.getName() ;

    delete client;

}

main.cpp

#include <QCoreApplication>
#include "myserver.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    myServer s;

    return a.exec();
}

Error picture :
left one is Client app and right one is Server app:

[Christian Ehrlicher]

Please take a look at the QDataStream documentation - you can't simply copy the (expected) Memory of your class - you have to (de)serialize your members of the class with the help of QDataStream.

[kshegunov]

@Anmol said in Send Custom class object using QtcpSocket and QtcpServer:

deserialize not working. after deserialize getName() [ myserver.cpp -- readredy() ] returns empty string

Your code is wrong.
You've written a memory address and then expect to read that memory address on the other side? It's not going to work like that. It's a small wonder it doesn't simply crash. Don't be lazy, write a couple of functions and serialize the data properly, which incidentally means: don't use reinterpret_cast, especially when you're not 100% sure what it does.

[Anmol]

i have created a method for writing all data into QByteArray and send it and then reading data from it at other side. its works perfectly.

Thanks for helping me.