QSslSocket::readyRead() signal is not raise after sending data ..



  • Hi,

    My program does not get a "readyRead" signal, when I have send data over the
    same socket.
    But when I add the line "m_sslSocket->waitForReadyRead(10);"

        m_sslSocket->write(*block);
        m_sslSocket->flush();                           
        m_StateMachineState=CommandSend;
        m_sslSocket->waitForReadyRead(10);
        delete  block;
    

    I will get the signal

    void    DataThread::SocketReadyRead(void)
    {
    QByteArray block;
    
        QDataStream inStream(m_sslSocket);
        inStream.setVersion(QDataStream::Qt_5_4);
        while (m_sslSocket->bytesAvailable() < 6 )
            {
            sleep(10);
            }
        inStream >> block;
    
        QString sAnswer(block.data());                 <<<    Answer correct received here 
        ...
    }
    ....
    

    I use the OS "kUbuntu 17.04" and QT 5.9.2 (free Version)

    Any Idea why I have to add the " m_sslSocket->waitForReadyRead(10);", because this will block
    the application, which I do not like.

    Best regards
    R.



  • @Ritchie
    Does waitForReadyRead(0) (i.e. 0 instead of 10) also ensure you get your readyRead signal consistently?

    Also/separately, if you do not put the m_sslSocket->waitForReadyRead(...); line in, your code just continues, so does it later go into an event loop so that the signal can be received?



  • @Ritchie said in QSslSocket::readyRead() signal is not raise after sending data ..:

    while (m_sslSocket->bytesAvailable() < 6 )
    {
    sleep(10);
    }

    You should not put delays and wait loops into slots. Never. It will block the event loop and therefore you will not receive your data.

    You cannot expect that all byte arrive at the first time the slot is called. Just buffer the data and leave the slot. It will be called again when further data arrives. Once you have enough data, start processing it.

    Also, as @JNBarchan already mentioned, is your event loop running?



  • @aha_1980
    The thing is, he claims that he does not receive signal at all unless he includes waitForReadyRead(). Or that is how I took his question. If that is the case, he does not get as far as that code, so although it's bad it's not executed.



  • @JNBarchan said in QSslSocket::readyRead() signal is not raise after sending data ..:

    If that is the case, he does not get as far as that code, so although it's bad it's not executed.

    That's what he said. But in programming, I don't believe anymore, I just verify. And I'm pretty sure his slot does not get over the while loop in the slot.

    Of course you may also be right that the event loop is not running at all. We'll see when we get more information.



  • @aha_1980 said in QSslSocket::readyRead() signal is not raise after sending data ..:

    @JNBarchan said in QSslSocket::readyRead() signal is not raise after sending data ..:
    That's what he said. But in programming, I don't believe anymore, I just verify.

    I couldn't agree with you more. But then I get into trouble! :)



  • @aha_1980

    The thing is, he claims that he does not receive signal at all unless he includes waitForReadyRead()

    Thats correct, If I remove the line "waitForReadyRead()", I do not get the event "ReadyRead".

    Best regards
    R.



  • @Ritchie said in QSslSocket::readyRead() signal is not raise after sending data ..:

    Thats correct, If I remove the line "waitForReadyRead()", I do not get the event "ReadyRead".

    And have you checked our hints?

    If your slot is connected, and the data comes in, the slot is called. So your problem must be somewhere else in your program. Really make sure you block then event loop, this is the most common reason for problems like yours.

    As you gave us only snippets of your program, this is the max. help we can give you.

    PS: And make sure you don't call blockSignals() - this was the reason for a timer not calling it's slot some days ago in this forum.



  • @Ritchie said in QSslSocket::readyRead() signal is not raise after sending data ..:

    m_sslSocket->write(*block);
    m_sslSocket->flush();                           
    m_StateMachineState=CommandSend;
    m_sslSocket->waitForReadyRead(10);
    delete  block;
    

    I believe you delete your block before write is finished, write is asynchronus after all.

    Try replacing delete block with:

    //With the assumption block is a Qbytearray
    connect(m_sslSocket, &QSslSocket::bytesWritten, block, &QByteArray::deleteLater);
    


  • @J.Hilk
    Since he calls m_sslSocket->flush();, and that says "This function writes as much as possible from the internal write buffer to the underlying network socket, without blocking", I'm assuming that we don't have an asynchronous/out of scope situation on block?

    Having said that, I'm not defending the design pattern, just questioning whether it will actually go wrong. Your deleteLater is a nicer pattern.



  • @JNBarchan
    Well we can narrow it down a bit by replacing waitForReadyRead with bool QIODevice::waitForBytesWritten(int msecs) and monitoring the time spend waiting:

    QElapsedTimer eT; et.start();
    m_sslSocket->write(*block);
    m_sslSocket->flush();                           
    m_StateMachineState=CommandSend;
    qDebug() << m_sslSocket->waitForBytesWritten(10) << "Time since write" << et.elapsed() << et.nsecsElapsed();
    delete  block;
    


  • @Ritchie
    At this point, unless you show/explain what your code does after the snippet you show (if you don't do the m_sslSocket->waitForReadyRead(10)), in the way of hitting an event loop, I don't think people can help you further.

    Alternatively, if you don't want to do that, I also suggested that a possible "workaround" in practice might be m_sslSocket->waitForReadyRead(0)), but you haven't commented on trying that either.



  • Thanks to all,

    I will update my program with your recommendations and come back
    with results.

    Best regards
    R.



  • Hi to all,
    @aha_1980
    I change the waiting function to

        if( m_sslSocket->bytesAvailable() < 6 )
            return;
    
    

    This works as well and will not block.
    Thanks for this info.

    Of course you may also be right that the event loop is not running at all. We'll see when we get more information.

    Is the event Loop for each thread or the complete system,
    because I have also run a front end and a second thread reading sensor values.

    PS: And make sure you don't call blockSignals() - this was the reason for a timer not calling it's slot some days ago in this forum.

    I do not use "blockSignals() " in my source code. Are there know functions of QT, which are using this function ?

    @J-Hilk

    I believe you delete your block before write is finished, write is asynchronus after all.

    Transmission to the server is working fine, since the connection is established.

    @JNBarchan
    waitForReadyRead(0) does not work.
    I check the value 5, which will work as the smallest value.
    But up to now, I am working locally and the server has to
    do a query in the database for the answer.
    See what happen later in real envirement (internet via mobil to the server).

    Your deleteLater is a nicer pattern.

    When I use deletelater, at which time will QT delete the object,
    because the function is call several times in a minute.

    Here is the complete code of the client

    //
    // C++ Implementation: Datathread
    //
    // Description: 
    //
    //
    // Author: 
    //
    // Copyright: See COPYING file that comes with this distribution
    //
    //
    #include			<QDebug>
    #include            <QSettings>
    #include			<QMessageBox>
    #include            <QThread>
    
    #include            "ProgramDiagnose.h"
    #include            "DataThread.h"
    
    extern			QString					ApplicationPath;        // Path of the exe File
    
    
    class           SensorValueData;
    
    // ************************************************************
    //				Constructor
    // ************************************************************
    
    DataThread::DataThread(int	*PPointer,SensorValueDatas *SensorBufferPointer, ProgrammDiagnosis    *DebugPointer)
    {
        m_ProgramIsRunning = PPointer;
        SensorQueryBuffer = SensorBufferPointer;
        ProgramInfo=DebugPointer;
        m_StateMachineState=NoConnection;
        loadSystemSettings();
    }
    
    // ************************************************************
    //			Destructor
    // ************************************************************
    DataThread::~DataThread()
    {
    }
    
    // **************************************************************************
    // Load the system settings of the thread
    // **************************************************************************
    void		DataThread::loadSystemSettings(void)
    {
    
        QSettings 				settings(ApplicationPath + "../config/carinfo.ini",QSettings::IniFormat);
    
        settings.beginGroup("DataServer");
        m_ServerTCPIPAddress	=settings.value("IP", "localhost").toString();		// Car Server Name
        m_ServerTCPIPPort		=settings.value("Port", "localhost").toInt();       // Name of the SQL Database;
        m_LocalSSLCertificate    =settings.value("SSLCertificate", "sslserver.pem").toString();         //
        settings.endGroup();
    
        settings.beginGroup("CustomerInfo");
        m_CustomerID            =settings.value("CustomerID", "-").toInt();      // Customer ID
        m_SerialNumber          =settings.value("SerialNo", "-").toString();
        m_CarType               =settings.value("CarType", "-").toString();
        settings.endGroup();
    }
    
    // ************************************************************
    //          Send out a record data set
    // ************************************************************
    void  DataThread::sendRecordData(void)
    {
    QByteArray					*block;										// Stream Buffer
    SensorValueData             *TempValue;
    
        m_blockSize=0;                                                      // clear the record size value
        m_NumberOfBytesSend=0;                                              // Clear the number of byte send
        TempValue = SensorQueryBuffer->getIndex(0);
        block	= new QByteArray;                                   		// create Stream Buffer
        m_Command.clear();
        m_ParameterType=RecordData;
        m_Command.addParameter((int)m_ParameterType);
        m_Command.setCommand(TCPIP_CMD_REQUEST_DATA);                        // data will be send to the server
    
        QDataStream			outStream(block, QIODevice::ReadWrite);         // just for write only
        outStream.setVersion(QDataStream::Qt_5_4);							// Set the version of stream
        outStream << (m_blockSize);											// Reserve memory for size
        outStream << m_Command ;											// Setup the command
        outStream << *TempValue;                                            // send out the Data
        outStream.device()->seek(0);										// jump back to the start of the block
        m_blockSize = (quint64)block->size();
        outStream << m_blockSize;                                           // write the size of data - size info into
        m_sslSocket->write(*block);											// Send data to the Server
        m_sslSocket->flush();                                               // send out the data to the server now
        m_StateMachineState=CommandSend;                                    //
        m_sslSocket->waitForReadyRead(5);
        delete  block;
    }
    
    // ************************************************************
    //				Run function of the thread
    // ************************************************************
    void DataThread::doWork(void)
    {
        ProgramInfo->writelog(QObject::tr("carclient"),QObject::tr("DataThread"),QObject::tr("Info"),QObject::tr("Thread startup"));
    
        m_sslSocket=new QSslSocket(this);
    
        connect(m_sslSocket,SIGNAL(disconnected(void)), this,SLOT(disconnected(void)));
        connect(m_sslSocket,SIGNAL(encrypted(void)), this, SLOT(SSLReady(void)));
    
        typedef void (QSslSocket::* sslErrorsSignal)(const QList<QSslError> &);
        connect(m_sslSocket, static_cast<sslErrorsSignal>(&QSslSocket::sslErrors),this, &DataThread::SSLError);
    
        connect(m_sslSocket,SIGNAL(readyRead(void)), this,SLOT(SocketReadyRead(void)));
        connect(m_sslSocket,SIGNAL(aboutToClose(void)), this,SLOT(aboutToClose(void)));
    //    connect(m_sslSocket,SIGNAL(bytesWritten(qint64)), this,SLOT(bytesWritten(qint64)));
    
        m_sslSocket->addCaCertificates(ApplicationPath + "../config/" + m_LocalSSLCertificate);
        if (! QSslSocket::supportsSsl())
            {
            ProgramInfo->writelog(QObject::tr("carclient"),QObject::tr("DataThread"),QObject::tr("Failure"),QObject::tr("No support fpr SSL connection!"));
            }
        QThread::msleep(4000);														// Wait a little bit
    //    m_sslSocket->ignoreSslErrors();
    
        while( *m_ProgramIsRunning == true )								// wait until program is close down
    		{
            if( SensorQueryBuffer->Size() > 0 )
                {
                if ( ! SensorQueryBuffer->locked() )
                    {
                    if (m_sslSocket->state() != QTcpSocket::ConnectedState)
                        {
                        if( m_StateMachineState == NoConnection )
                            {
                            m_StateMachineState=TryToConnect;
                            m_sslSocket->connectToHostEncrypted(m_ServerTCPIPAddress, m_ServerTCPIPPort);
                            m_sslSocket->waitForEncrypted(-1);
                            }
                        }
                    }
                }
    		}
    
       if( m_StateMachineState != NoConnection )
        {
        m_sslSocket->close();
        m_sslSocket->disconnectFromHost();
        }
        emit    WorkFinished();
    }
    
    // ************************************************************
    //          Connection was disconnected
    // ************************************************************
    void    DataThread::disconnected(void)
    {
        SensorQueryBuffer->clearLock();                     // release lock of the data
        m_StateMachineState=NoConnection;                   // State to disconnected
    }
    
    // ************************************************************
    //          Host is found from Client
    // ************************************************************
    void    DataThread::hostFound(void)
    {
    }
    
    // ************************************************************
    //              SSL Connection established
    // ************************************************************
    void    DataThread::SSLReady(void)
    {
        if( m_StateMachineState !=CommandSend )
            {
            m_StateMachineState=SocketConnected;
            SensorQueryBuffer->setLocked();
            sendRecordData();                                      // Send out the data
            }
    }
    
    // ************************************************************
    //      We get a new connection. Send out the command
    // ************************************************************
    void    DataThread::connected(void)
    {
    }
    
    // ************************************************************
    //      There was a error inbetween the transmission
    // ************************************************************
    void    DataThread::SSLError(const QList<QSslError> errors)
    {
        m_LastErrorMessage=m_sslSocket->errorString();
    //    m_sslSocket->ignoreSslErrors( );
        SensorQueryBuffer->clearLock();
        m_sslSocket->disconnectFromHost();
        m_StateMachineState=NoConnection;                   // State to disconnected
        m_sslSocket->close();
    
        ProgramInfo->writelog(tr("carclient"),
                              tr("DataThread"),
                             tr("Error on Connection %3"),
                             tr("Data Background Abort 1 Function (%1::%2)!").arg(m_ServerTCPIPAddress).arg(m_ServerTCPIPPort).arg(m_LastErrorMessage));
    
    //    emit showMessageFromThread(tr("Critical System Error"),
    //                            tr("DataThread (%1::%2)!").arg(m_ServerTCPIPAddress).arg(m_ServerTCPIPPort),
    //                            tr("Error %1 on Connection !").arg(m_LastErrorMessage),
    //                           (int)QMessageBox::Critical );
    }
    
    // ************************************************************
    //      Client receiveds byte from Server
    // ************************************************************
    void    DataThread::SocketReadyRead(void)
    {
    QByteArray block;
    
    
        if( m_sslSocket->bytesAvailable() < 6 )
            return;
    
        QDataStream inStream(m_sslSocket);                 // Create a data stream by tcp/ip
        inStream.setVersion(QDataStream::Qt_5_4);           // we are using version .. for Transmission
    
        inStream >> block;
    
        QString sAnswer(block.data());
    
        switch(m_ParameterType)
            {
            case    NoParameter:
                    break;
            case    RecordData:
                    if(sAnswer == "OK")
                        {
                        SensorQueryBuffer->remove(0);      // remove value only if transmitted
                        }
                    SensorQueryBuffer->clearLock();        // release lock of the data
                    break;
            case    CustomerData:
                    break;
            case    LastPosition:
                    break;
            }
    
    
         m_sslSocket->disconnectFromHost();
         m_sslSocket->close();
         m_StateMachineState=NoConnection;
    }
    
    // ************************************************************
    //          Connection is about to close
    // ************************************************************
    void    DataThread::aboutToClose(void)
    {
        m_StateMachineState=NoConnection;                   // State to disconnected
        SensorQueryBuffer->clearLock();                     // release lock of the data
    }
    
    // ************************************************************
    // Do we have send out all datas to the server
    // ************************************************************
    void    DataThread::bytesWritten(qint64 NumberOfBytes)
    {
        m_NumberOfBytesSend += NumberOfBytes;
        if(m_NumberOfBytesSend == m_blockSize)
            {
            switch(m_ParameterType)
                {
                case    NoParameter:
                        break;
                case    RecordData:
                        break;
                case    CustomerData:
                        break;
                case    LastPosition:
                        break;
                }
            }
    }
    

    Best regards
    R.


  • Lifetime Qt Champion

    Hi,

    Out of curiosity, why allocate block on the heap ? Since you delete it anyway at the end of the function, just allocate it on the stack. You'll avoid all the troubles you had with deleting it by hand before it was completely sent.



  • @Ritchie:
    I just saw from your last code that you also have m_sslSocket->waitForEncrypted(-1);. In principle, I would avoid mixing the waitForXxx() functions with the signal-slot mechanism.

    I also just recognized, that your code runs within a thread, correct? Using blocking functions is totally valid in threads, but as said above, I'd not mix this with signals-slots.

    Further, a thread does not use the event loop of your main program. If you want to use slots in your thread, than you need to implement an event loop for it. Emitting signals from within you thread (e.g. to the main thread) is always possible, but using slots within your thread needs an separate event loop.

    And maybe this is already the problem why your slot is only called when you have the waitForReadyRead() function active?



  • @aha_1980
    But when I remove the line

    m_sslSocket->waitForEncrypted(-1);
    

    the complete communication will not established.

    This was posted here:
    https://forum.qt.io/topic/84370/create-a-ssl-connection-only-with-slots-and-signals

    There is also a sample program posted (download because of to big files).

    I do not get the "encrypted()" signals in this case and I do not know, why.
    But with the "m_sslSocket->waitForEncrypted(-1);" I got the signal.

    Best regards
    R.



  • Hi,

    I just reinstall the complete system to make sure that it is not my installation.
    But the problem is still existing.

    • The server program receives a request for a new connection and start a new instance of the SSLSocket.

    But after the command

    m_sslSocket->startServerEncryption();
    

    on the server nothing happens on the client. Still!

    But now I at a slot

        connect(m_sslSocket,SIGNAL(connected(void)), this, SLOT(ConnectionEstablished(void)));
    

    and noticed, that when I close my frontend application which is working
    like the sample application of QML, here the start code of the window

        QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
        QGuiApplication app(argc, argv);
    
        app.setOrganizationName(CLIENT_PROGRAM_NAME);
        QTextCodec::setCodecForLocale( QTextCodec::codecForName("UTF-8") );
        QLocale::setDefault(QLocale::German);
        QQuickStyle::setStyle(QStringLiteral("qrc:/qml/Style"));
        QQmlApplicationEngine engine;
        engine.rootContext()->setContextProperty("BackEnd", &UserDisplay);
        engine.load(QUrl(QStringLiteral("qrc:/client.qml")));
    

    i receive a "Connected" signal.

    That sounds for my, that my QML Application is blocking signals, which I do not know.

    Is it allow to have a front end, like the sample program and running a back ground program for communication ?

    Best regards
    R.



  • @Ritchie we already gave you some pointers.

    Again: don't mix waitForReadyXxxx() with signals&slots!

    If your complete program is not working, its often best to start from scratch with a minimal working example. then build your way to a full program. when you stuck, ask specific questions, we may then be able to help you. most often you can answer you question yourself already.



  • Hi,

    Again: don't mix waitForReadyXxxx() with signals&slots!

    I do not use any "waitForReadyXxxx()" within my program.
    I used once "m_sslSocket->waitForReadyRead(10);" to show, that suddenly a change was happen. But it solve not my problem.

    Anyways I guess the main reason why it does not work it,
    that I have to call "QThread:exec()" with the thread once to support signal and slots in the QThread.

    But when I call "QThread:exec()" I will not execute any other code in the class.

    But I would like to execute the loop which is coded in the function "void DataThread::doWork(void)"

    How can I execute "void DataThread::doWork(void)" and let "Qthread:exec()" have at the same time ?

    Best regards
    R.


  • Lifetime Qt Champion

    You should take a look at the example provided in the QThread details documentation more specifically the one for the worker object implementation.



  • Hi,

    I am already using the first way, shown in the examples.

    But the documents says:

    A QThread object manages one thread of control within the program. QThreads begin executing in run(). By default, run() starts the event loop by calling exec() and runs a Qt event loop inside the thread.

    So, if I not execute the "Exec()" command, so far I understand, the QT Event Loop will not starts.

    But within the examples, there is no using any "exec()".

    It says for the first sample:

    The code inside the Worker's slot would then execute in a separate thread. However, you are free to connect the Worker's slots to any signal, from any object, in any thread. It is safe to connect signals and slots across different threads, thanks to a mechanism called queued connections.

    So in this case, no "exec()" is needed in the separate thread to execute ?

    And for the second sample it says

    In that example, the thread will exit after the run function has returned. There will not be any event loop running in the thread unless you call exec().

    Best regards
    R.



  • @Ritchie I'm assuming your "program" is a client connecting securely to a server, because you're using

    m_sslSocket->write(*block);
    m_sslSocket->flush(); 
    

    so I don't getting why you're expecting a readyRead() signal, since that will happen when you are reading data, not writing it. From Qt's documentation:

    void QIODevice::readyRead()

    This signal is emitted once every time new data is available for reading from the device's current read channel.

    Am I missing something? If so my apologies right now...



  • @Pablo-J-Rogina
    You are right, the

    void QIODevice::readyRead()

    is only emitted after receiving bytes from the server.
    And after sending data's from the client to the server, the server will answer.

    Like "Data stored" correct or "Data not stored"

    Best regards
    R.



  • Hi to all,

    I solved my problem by the following way.

    The function "DoWork" was change in the follwing way. Now it calls the QThread::exec() function.
    The loop function is done by a timer event.

    void DataThread::doWork(void)
    {
        ProgramInfo->writelog(QObject::tr("carclient"),QObject::tr("DataThread"),QObject::tr("Info"),QObject::tr("Thread startup"));
    
        if (! m_sslSocket->supportsSsl())
            {
            ProgramInfo->writelog(QObject::tr("carclient"),QObject::tr("DataThread"),QObject::tr("Failure"),QObject::tr("No support fpr SSL connection!"));
            }
    
        m_WorkTimer = new QTimer();
        connect(m_WorkTimer, SIGNAL(timeout()), this, SLOT(DoTimerWork()));
        m_WorkTimer->start(50);
    
        QThread::exec();
    
        m_WorkTimer->stop();  // will delete later
    
       if( m_StateMachineState != NoConnection )
        {
        m_sslSocket->close();
        m_sslSocket->disconnectFromHost();
        }
        emit    WorkFinished();
    }
    

    Within the function "DoTimerWork", I do the cyclic stuff and do not block the events anymore

    void    DataThread::DoTimerWork(void)
    {
        if( SensorQueryBuffer->Size() > 0 )
            {
            if ( ! SensorQueryBuffer->locked() )
                {
                if (m_sslSocket->state() != QTcpSocket::ConnectedState)
                    {
                    if( m_StateMachineState == NoConnection )
                        {
                        m_StateMachineState=TryToConnect;
                        m_sslSocket->connectToHostEncrypted(m_ServerTCPIPAddress, m_ServerTCPIPPort);
                        }
                    }
                }
            }
    }
    
    

    Thanks to all try to help me.

    Best regards
    R.


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