multi threading send data to clients

Mogli123

Hi,

I would to send datas (QString) from a qt-project to another, via qtcpserver.
I have the code from the following example
QTcpServer Multithreaded Client
but I don't know how to send my data to the clients.
I can only send data once at the beginning when the client is connecting to the server.
I hope somewone can giv me a tip or a pice of code.

This is my code.

mytcpserver.h

#include <QObject>
#include <QTcpServer>
#include <QtDebug>
#include "mythread.h"

class MyTcpServer : public QTcpServer
{
    Q_OBJECT
public:
    explicit MyTcpServer(QObject *parent = nullptr);
    void StartServer();

signals:
    void sendData(QString sendData);

public slots:
    void dataToSend(QString dataToSend);


private:
    MyThread *mThread;

protected:
    void incomingConnection(qintptr socketDescriptor);

mythread.h

#include <QObject>
#include <QThread>
#include <QTcpSocket>
#include <QDebug>

class MyThread : public QThread
{
    Q_OBJECT
public:
    explicit MyThread(int ID, QObject *parent = nullptr);
    void run();

signals:
    void error(QTcpSocket::SocketError socketerror);


public slots:
    void readyRead();
    void disconnected();

private:
    QTcpSocket *client;
    int socketDescriptor;

};

myserver.cpp

MyTcpServer::MyTcpServer(QObject *parent) :
    QTcpServer(parent)
{
}

void MyTcpServer::StartServer()
{
    if (!this->listen(QHostAddress::Any,5000))
    {
        qDebug()<< "second Could not start server";
    }
    else
    {
     qDebug()<<"Listening...";
    }
}

void MyTcpServer::incomingConnection(qintptr socketDescriptor)
{
    qDebug()<< socketDescriptor<<"Connecting...";
    MyThread *thread = new MyThread(socketDescriptor, this);
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    thread->start();
}

void MyTcpServer::dataToSend(QString toSendData)
{
    mclient->waitForReadyRead(300);
//  schickt den empfangenen String an die Verbundenen Clients
    mclient->write("Pushservice TCP-Client:" + toSendData.toUtf8());
    mclient->flush();
    qDebug()<<toSendData;
}

mythread.cpp

MyThread::MyThread(int ID, QObject *parent) :
    QThread(parent)
{
// übergibt die ID
    this->socketDescriptor = ID;
}

void MyThread::run()
{
    //thread starts here
    qDebug()<<socketDescriptor<<"Starting thread";
    client = new QTcpSocket();
    if(!client->setSocketDescriptor(this->socketDescriptor))
    {
        emit error(client->error());
        return;
    }

    connect(client,SIGNAL(readyRead()),this,SLOT(readyRead()),Qt::DirectConnection);
    connect(client,SIGNAL(disconnected()),this,SLOT(disconnected()),Qt::DirectConnection);

    qDebug()<<socketDescriptor<<"Client Connected";
    client->write("mythread is writting");
    exec();
}

void MyThread::readyRead()
{
    QByteArray data = client->readAll();

    qDebug()<< socketDescriptor << "Data in:"<<data;

    client->write("data");

}

void MyThread::disconnected()
{
    qDebug()<< socketDescriptor << "Disconnected";
    client->deleteLater();
    exit(0);
}

Thank you in advance.

Regards

VRonin

many of us agree that the examples available on the topic are too limited or even downright misleading so we put together another one: https://wiki.qt.io/index.php?title=WIP-How_to_create_a_simple_chat_application that example should help you given it sends "strings" in the form of JSON documents

Mogli123

@VRonin
Thank you
i will try it

kshegunov

@Mogli123 said in multi threading send data to clients:

QTcpServer Multithreaded Client

This example is bogus, don't use it.
Here's your hint:

Note that Qt::DirectConnection is used for the readyRead connection. This is because it's multithreaded, otherwise we may have some operation issues. This makes the slot to be invoked immediately, when the signal is emitted.

False statement and if you follow the code leading to this paragraph you're going to see this is due to the person who wrote the code has no idea what (s)he's doing. It's a race condition in the socket reading.