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Thread: Multithreaded Server, Timer in QThread, Thread IDs questions

  1. 23rd April 2010, 12:14 #1
    sadjoker
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    Question Multithreaded Server, Timer in QThread, Thread IDs questions

    Hello, in order to understand the multithreaded applications deeper i have some questions:

    I have an application (server accepting clients trough SSL opening new thread for every client). Every thread makes new PSQL connection cloned from main connection with unique name.

    I needed to make a QTimer to disconnect idled connections and threads so i open the new Thread with parent 0 and i call moveToThread( this ) in the thread`s constructor. The timer starts and resets in the readData() slot called from the readyRead() signal of the QSSlSocket which i open in the run() function of the inherited QThread class.

    When i call currentThreadId() after moveToThread(this) the ID is the main thread`s ID... but called from run() method it shows new thread ID. When i call quit or exit the destructor of the inherited class is never called but the slot of thread`s finished signal is called and the thread id there is again main thread`s id.

    My questions are...
    1. Why in the thread`s constructor the currentThreadID is main thread`s id after moveToThread(this). ( i read that QThread`s object lives in the thread which is calling it so i assume it`s normal showing the main thread`s ID but am i doing it right?)
    2. Why the destructor of the QThread is not called (i recall a time when i saw it running before i fiddle with the QTimer`s stuff). The thread is closing because i watch it with OllyDbg but i still don`t understand the process.
    3. Is it ok to use Qt:irectConnection in this:
    Qt Code: 
    1. connect(serverSocket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(errorSlot(QAbstractSocket::SocketError)), Qt::DirectConnection);
    2.     connect(serverSocket, SIGNAL(disconnected()), this, SLOT(connectionClosed()), Qt::DirectConnection);
    3.     connect(serverSocket, SIGNAL(readyRead()), this, SLOT(readData()), Qt::DirectConnection);
    4.     connect(serverSocket, SIGNAL(sslErrors(const QList<QSslError>&)), this, SLOT(sslErrors(const QList<QSslError>&)), Qt::DirectConnection);
    5.     connect(serverSocket, SIGNAL(encrypted()), this, SLOT(ready()), Qt::DirectConnection);
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    because IF i don`t i have to use qRegisterMetaType for the types in the SLOT() and i`m getting really weird random crashes.

    Here some code:

    SSLServer.cpp

    Qt Code: 
    1. #include "SSLserver.h"
    2.  
    3. SSLServer::SSLServer(quint16 port, QObject* parent)
    4.   : QTcpServer(parent)
    5. {
    6.   if(!listen(QHostAddress::Any, port))
    7.     {
    8.       QMessageBox::critical(0, "Error!", tr("Server cannot listen at port %1!").arg(port), QMessageBox::Ok);
    9.       exit(5);
    10.   }
    11. }
    12.  
    13. void SSLServer::incomingConnection(int socketDescriptor)
    14. {
    15.   qDebug() << "OPening new Thread from sslserver TID: " << QThread::currentThreadId();// SHOW MAIN THREAD ID
    16.   thread = new SSLThread(socketDescriptor, 0);// HERE OPEN NEW THREAD WITH PARENT 0
    17.   connect(thread, SIGNAL(finished()), this, SLOT(fin()));
    18.   connect(thread, SIGNAL(messageToGui(QString)), QObject::parent(), SLOT(writeToLogs(QString)));
    19.   connect(thread, SIGNAL(addRegisteredUser(QString)), QObject::parent(), SLOT(addUserToList(QString)));
    20.   connect(thread, SIGNAL(delRegisteredUser(QString)), QObject::parent(), SLOT(removeUserFromList(QString)));
    21.   thread->start();
    22. }
    23.  
    24. void SSLServer::fin()
    25. {
    26.     qDebug() << "Closing Thread ID (from sslserver): " << thread->currentThreadId();// HERE SHOWS MAIN THREAD ID
    27.     thread->deleteLater();
    28. }
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    SSLThread.cpp

    Qt Code: 
    1. #include "SSLthread.h"
    2. #include <QtNetwork>
    3.  
    4. SSLThread::SSLThread(int socketDr, QObject* parent) : QThread(parent)
    5. {
    6.     moveToThread( this );
    7.     socketDescriptor = socketDr;
    8. .....
    9.     qDebug() << "ThreadID from constructor: " << currentThreadId();//SHOWS MAIN THREAD ID ??????
    10. }
    11.  
    12. SSLThread::~SSLThread()
    13. {
    14.     qDebug() << ">>>Destructor<<<";
    15. //NEVER CALLED
    16. }
    17.  
    18. void SSLThread::run()
    19. {
    20.     qDebug() << "ThreadID: " << currentThreadId();//SHOWS NEW THREAD ID
    21.     serverSocket = new QSslSocket();
    22.     serverSocket->setProtocol(QSsl::AnyProtocol);
    23.     serverSocket->setPeerVerifyMode(QSslSocket::VerifyNone);
    24.     serverSocket->setDefaultCiphers(serverSocket->supportedCiphers());
    25.     connect(serverSocket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(errorSlot(QAbstractSocket::SocketError)), Qt::DirectConnection);
    26.     connect(serverSocket, SIGNAL(disconnected()), this, SLOT(connectionClosed()), Qt::DirectConnection);
    27.     connect(serverSocket, SIGNAL(readyRead()), this, SLOT(readData()), Qt::DirectConnection);
    28.     connect(serverSocket, SIGNAL(sslErrors(const QList<QSslError>&)), this, SLOT(sslErrors(const QList<QSslError>&)), Qt::DirectConnection);
    29.     connect(serverSocket, SIGNAL(encrypted()), this, SLOT(ready()), Qt::DirectConnection);
    30.     //connect(serverSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(stateChanged(QAbstractSocket::SocketState)), Qt::DirectConnection);
    31.     connect(serverSocket, SIGNAL(modeChanged(QSslSocket::SslMode)), this, SLOT(sslModeChanged(QSslSocket::SslMode)), Qt::DirectConnection);
    32.     timerTimeout = new QTimer(this);timerTimeout->setSingleShot(true);
    33.     connect(timerTimeout, SIGNAL(timeout()), this, SLOT(timeOut()));
    34.  
    35.  
    36.   .....(reading certificates and running stuff)
    37.     exec();
    38. }
    39.  
    40. void SSLThread::connectionClosed()
    41. {
    42.     qDebug() << "ThreadID: " << currentThreadId();
    43.     QSqlDatabase db = QSqlDatabase::database(uid);
    44.     if (db.isOpen())
    45.         db.close();
    46.     if (serverSocket->state() == QAbstractSocket::ClosingState)
    47.     {
    48.         connect(serverSocket, SIGNAL(disconnected()), SLOT(deleteLater()));
    49.     }
    50.     else
    51.     {
    52.         serverSocket->deleteLater();
    53.     }
    54.     emit delRegisteredUser(authUserName);
    55.     emit messageToGui(tr("%1 %2  quits the system.").arg(QTime::currentTime().toString()).arg(authUserName));
    56.     authUserName.clear();
    57.     if(timerTimeout)
    58.         timerTimeout->deleteLater();
    59.     qDebug("Connection closed.");
    60.     exit(0);
    61. }
    62.  
    63. void SSLThread::timeOut()
    64. {
    65.     if(timerTimeout->isActive())
    66.         timerTimeout->stop();
    67.  
    68.     serverSocket->close();
    69.     qDebug() << "ThreadID: " << currentThreadId();
    70. }
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    Now the server is running fine.. it accepts connections, reads all the data, disconnects the clients fine... but i`m worried if i`m doing things properly. Also i`m worried if everything is cleaned properly... it`s important because that server should be 24/7 and memory leaks are not very welcome. Thank you in advance!
    Last edited by sadjoker; 23rd April 2010 at 12:27.
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  2. 23rd April 2010, 13:23 #2
    sadjoker
    sadjoker is offline Novice
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    Default Re: Multithreaded Server, Timer in QThread, Thread IDs questions

    Changing

    Qt Code: 
    1. connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
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    into SSLServer.cpp fixed a bug with not executing the timers of the next threads.
    Last edited by sadjoker; 23rd April 2010 at 13:33.
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