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My gui have a two button's, one to start a server & other to stop a server.

Brief :---
Once server is started, on every new client request i will create a new thread & this will handle communication with the client.

Detail :--
When start button is pressed, I am creating an object 'tcpserverobjectWrapper' which creates an another object 'tcpserverobject' this object creats an Qtcpserver. Now this Qtcpserver is listing for new connection. And when a new connection comes i create an 'TcpSocketThreadWrapperObject' object which creates a thread & this thread handles communication with client . Also 'tcpserverobject' keeps the list of new client request objects created 'QList<TcpSocketThreadWrapperObject *> TcpSocketThreadWrapperObjectList;' .

I am able to connect to server from telnet clients & it creates new thread for each client & works fine.

When stop button pressed i am able to stop server & client threads.

But i have two problems here :---
1> Everytime client send some data to server. I get this kind of QsocketNotifier. What is this ?

QSocketNotifier: socket notifiers cannot be enabled from another thread
QSocketNotifier: socket notifiers cannot be disabled from another thread

2> If i press stop button on GUI i am able to stop the threads succesfully.

But how to stop the threads & delete the objects created for every client when client send 'STOP command' to server or closes the connection with server ?
I will also have to delete the following objects created on each client request ?
client request --> TcpSocketThreadWrapperObject -- creates --> TcpSocketThreadObject -- creates --> TcpSocketThreadObject

Can someone suggest how to solve above two problems ? Reply on this will be appreciated.

Here is the code :---

================= start & stop buttons handler =====

void MainWindow::on_actionStop_triggered()
{
    if(b_threadAlreadyStarted)
    {

    /* ------------------ Tcp server object ------------------------*/

        b_threadAlreadyStarted = false;
        delete p_tcpserverobjectWrapper;

    /* ------------------ Tcp server object ------------------------*/

    }

}



void MainWindow::on_actionStart_triggered()
{

    if(!b_threadAlreadyStarted)
    {

    /* ------------------ Tcp server object ------------------------*/

        b_threadAlreadyStarted =true;

        p_tcpserverobjectWrapper = new tcpserverobjectWrapper(this,modelCANalyzer);

        qDebug() << " \n start ";

    /* ------------------ Tcp server object ------------------------*/

    }
}

======== tcpserverobjectWrapper class ===============

// Main server object wrapper
class tcpserverobjectWrapper : public QObject
{
    Q_OBJECT
public:
    explicit tcpserverobjectWrapper(QMainWindow *ptrWidget, QStandardItemModel *modelCANalyzer, QObject *parent=0);
    ~tcpserverobjectWrapper();

    //Device thread object
    tcpserverobject *m_tcpserverobject;
};



tcpserverobjectWrapper::tcpserverobjectWrapper(QMainWindow *ptrWidget , QStandardItemModel *modelCANalyzer,QObject *parent) :
    QObject(parent)
{
    m_tcpserverobject = new tcpserverobject ;

    //save model
    m_tcpserverobject->modeltable = modelCANalyzer;
    m_tcpserverobject->ptrmainwindow = ptrWidget;


    qDebug() << "\n tcp server thread started";

}

tcpserverobjectWrapper::~tcpserverobjectWrapper()
{

    qDebug() << " \n called delete later on tcpserverobjectWrapper .. !!";

    m_tcpserverobject->deleteLater();   // ---------------------> change it to - delete m_tcpserverobject

    qDebug() << " \n tcp server object successfully quited .. !! ";
}

========== tcpserverobject object ==================

class tcpserverobject : public QObject
{
    Q_OBJECT
public:
    explicit tcpserverobject(QObject *parent = 0);
    ~tcpserverobject();

    /*!
        Pointer to QStandardItemModel to be used inside - canTableView
    */
    QStandardItemModel *modeltable;

    //mainwindow pointer
    QMainWindow *ptrmainwindow;

    // Create list of new -- socket thread wrapper objects
    QList<TcpSocketThreadWrapperObject *> TcpSocketThreadWrapperObjectList;

private:
    QTcpServer *tcpServer;

signals:

public slots:

    void on_newConnection();

};

tcpserverobject::tcpserverobject(QObject *parent) :
    QObject(parent), tcpServer(0)
{
    tcpServer = new QTcpServer;

    // Connect slot of the server
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(on_newConnection()));

    //lisen on socket
    if (!tcpServer->listen(QHostAddress::LocalHost, SERVER_PORT )) {

        qDebug() << "\n returning from server listning error .. !!! ";

        return;
    }

    qDebug() << "\n server listning";

}

tcpserverobject::~tcpserverobject()
{

   // to do
    while (!TcpSocketThreadWrapperObjectList.isEmpty())
        delete TcpSocketThreadWrapperObjectList.takeFirst();
}

void tcpserverobject::on_newConnection()
{
    QByteArray block;

    block.append(" \n Hello from server .. !!!") ;

    QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
                clientConnection, SLOT(deleteLater()));

    // Create new thread for this .. client request ..!!
    qDebug() << "\n New connection request ..!!!";
    qDebug() << "\n New client from:" << clientConnection->peerAddress().toString();

    clientConnection->write(block);
    clientConnection->flush();

    // create new tcp object
    TcpSocketThreadWrapperObject* TcpSocketThreadWrapperObjectPtr = new TcpSocketThreadWrapperObject(clientConnection);

    // Append object to the list
    TcpSocketThreadWrapperObjectList.append(TcpSocketThreadWrapperObjectPtr);

}

============ TcpSocketThreadWrapperObject ==============

// Main device thread object
class TcpSocketThreadWrapperObject : public QObject
{
    Q_OBJECT
public:
    explicit TcpSocketThreadWrapperObject(QTcpSocket *m_pTcpSocket , QObject *parent = 0);
    ~TcpSocketThreadWrapperObject();

    /*!
        pointer for write thread
    */
    QThread m_TcpSocketRWThread;

    /// pointer to the socketthread  object
    class TcpSocketThreadObject *m_pTcpSocketThreadObject;


signals:

public slots:

};


// constructor for the deviceThreadObject
TcpSocketThreadWrapperObject::TcpSocketThreadWrapperObject(QTcpSocket *m_pTcpSocket , QObject *parent) :
    QObject(parent)
{
    m_pTcpSocketThreadObject = new TcpSocketThreadObject(m_pTcpSocket);

    //set flag for event loop -- make while(1)
    m_pTcpSocketThreadObject->m_bQuit = false;
    // connect the signal & slot
    connect(&m_TcpSocketRWThread,SIGNAL(started()),m_pTcpSocketThreadObject,SLOT(dowork_socket()));
    // Move thread to object
    m_pTcpSocketThreadObject->moveToThread(&m_TcpSocketRWThread);

    //Start the thread
    m_TcpSocketRWThread.start();

}

TcpSocketThreadWrapperObject::~TcpSocketThreadWrapperObject()
{

    //set flag for event loop -- make while(0)
    m_pTcpSocketThreadObject->m_bQuit = false;

    // Wait for the thread to terminate
    m_TcpSocketRWThread.quit();
    m_TcpSocketRWThread.wait();

    // Delete the object
    m_pTcpSocketThreadObject->deleteLater();

    qDebug() << "\n deleted - TcpSocketThreadWrapperObject";

}

======== TcpSocketThreadObject object ========

class TcpSocketThreadObject : public QObject
{
    Q_OBJECT
public:
    explicit TcpSocketThreadObject(QTcpSocket *m_pTcpSocketTemp , QObject *parent = 0);
    ~TcpSocketThreadObject();

    /*!
        Pointer to TCP socket -- created by the server
    */
    QTcpSocket *m_pclientConnectionSocket;


    /*!
      Termination control main thread
    */
    volatile  bool m_bQuit;

signals:

public slots:
    void dowork_socket();

};


// constructor for the deviceThreadObject
TcpSocketThreadObject::TcpSocketThreadObject(QTcpSocket *m_pTcpSocketTemp , QObject *parent) :
    QObject(parent)
{
    m_pclientConnectionSocket = m_pTcpSocketTemp;

    // todo
}

TcpSocketThreadObject::~TcpSocketThreadObject()
{
    // todo

}

void TcpSocketThreadObject::dowork_socket()
{
    QByteArray block;

    block.append(" \n hi again .. !!!") ;

    // Write to socket
    m_pclientConnectionSocket->write(block);
    m_pclientConnectionSocket->flush();

    // Close socket
    m_pclientConnectionSocket->disconnectFromHost();
    qDebug() << "\n entring loop of socket thread ..!!!";

    while(!m_bQuit)
    {
        // while loop --> send/rx command from client
    }

}

======= output of one client connected to server =====

 New connection request ..!!! 

 New client from: "127.0.0.1" 
QSocketNotifier: socket notifiers cannot be enabled from another thread
QSocketNotifier: socket notifiers cannot be disabled from another thread

 entring loop of socket thread ..!!! 
Katoch
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1 Answers1

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I think the simplest solution to all of this is to stop using QThread.

QTcpSocket and QTcpServer are both asynchronous, so when you receive a connection, you only need to create a class to wrap the QTcpSocket and this class handles the reading of the data, having connected the QTcpSocket signals to the class's slots.

If you're getting a lot of connections, then you'll be creating lots of threads. More threads than processor cores is just a waste of time.

If each connection is requesting a lot of work to be done by the server, you can then create separate worker objects and move those to a different thread, but overall, I recommend that you do not use separate threads for QTcpServer and QTcpSockets.

TheDarkKnight
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