Qthreads in QT Creator

Question

I created a server in QT Creator, and also implemented the Threads service in it. But when I connect to the server, with the application "Client" and send a data, the server does not receive ... He should receive and print the received data, but this is not happening... I’ll post the server code here, if anyone knows how to fix thank you!

Note: I already did a test with the client, sending data to a server without the threading service, and the server received it. That is, the client is working normally... I believe something is wrong with the threads on this server.

mythread. h

#ifndef THREAD_H
#define THREAD_H

#include <QThread>
#include <QTcpSocket>
#include <QTcpServer>

class MyThread : public QThread
{
    Q_OBJECT
public:
    explicit MyThread(int ID, QObject *parent = 0);
    void run();

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

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

private:
    QTcpSocket *socket;
    int socketDescriptor;

};

#endif // THREAD_H

mythread. c

 #include "mythread.h"

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

void MyThread::run() {
    qDebug() << "Starting thread";
    socket = new QTcpSocket();

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

    if(!socket->setSocketDescriptor(this->socketDescriptor)) {
        emit error(socket->error());
        return;
    }

    qDebug() << "Client connected";
}

void MyThread::readyRead() {
    QByteArray data = socket->readAll();
    qDebug()<< data;
    socket->write(data);
}

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

server. c

#include "server.h"

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

void Server::StartServer() {

    if(!this->listen(QHostAddress::Any, 10000)) {
        qDebug() << "Could not start server";
    } else {
        qDebug() << "Listening...";
    }
}

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

server. h

#ifndef SERVER_H
#define SERVER_H

#include <QTcpServer>
#include <QDebug>
#include "mythread.h"


class Server : public QTcpServer
{
    Q_OBJECT
public:
    explicit Server(QObject *parent = 0);
    void StartServer();

signals:

public slots:

protected:
    void incomingConnection(int socketDescriptor);

};

#endif // SERVER_H

main. c

#include <QCoreApplication>
#include "server.h"
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    Server server;
    server.StartServer();
    return a.exec();
}

Answer 1

The problem is in your method MyThread::run(), when it comes to the end thread associated with it is also finalized or is there nor time of your socket wait for new connections.

Another important point is that in the new thread there is no event loop to process the events of QObjects created on her, this includes her socket.

Conclusion, besides being destroyed at the same time it was created, after the method and the thread be closed, their socket is also unable to process signals.

At the end of MyThread::run() add:

this->exec();

Using QThread::exec() you prevents that MyThread::run() return, keeping the thread active, and allows that the events of QObjects created within it can be processed.

You can read more on Qthread.