Threaded SSLServer using QSslSocket With bidirectional communication (avoid "QSocketNotifier: Socket notifiers cannot ...")

[Ritchie]

Hi,

I have written a SSL Server with threaded socket handling, which works fine
until I have only a one way communication.

Since I try to add a bidirectional communication, I get the "QSocketNotifier: Socket notifiers cannot ..." message.

The reason for this I mostly understand, because of the socket was created in other thread and can not be modified by
other thread.

But how do I have to create a socket, which can handled in other thread with read and write to connected client ?
Each thread can give different answers to the connected clients.

Best regards
R.

[SGaist]

Hi,

So you are moving your sockets around in different threads ? Can you explain your architecture in more details ?

[Ritchie]

@SGaist
I have a base window which will handle the SSLServer listen function

  m_SSLServer->setSslProtocol(QSsl::TlsV1_2);

    if (!m_SSLServer->listen(QHostAddress::Any,sTCPIPPort.toInt(&ok, 10)))
       ...

Based on the signal "incomingConnection"

   void incomingConnection(qintptr socketDescriptor) override final;

a thread with the actual socketdescriptor will created by

   QThread* SSL_thread = new QThread;
    TCPThread *m_task = new TCPThread(socketDescriptor,&m_SQLDatabase);   // Create thread object for transmission
    m_task->moveToThread(SSL_thread);

    connect( SSL_thread, SIGNAL(started()), m_task, SLOT(doWork()) );
    connect( m_task, SIGNAL(WorkFinished()), SSL_thread, SLOT(quit()) );

    //automatically delete thread and task object when work is done:
    connect(SSL_thread, SIGNAL(finished()), m_task, SLOT(deleteLater()));	// Setup stuff by closing the thread
    connect(SSL_thread, SIGNAL(finished()), SSL_thread, SLOT(deleteLater()) );
//    connect(SSL_thread, SIGNAL(TCPThreadError(QString,int)),
//                        this, SLOT(ShowTCPThreadError(QString,int)));		// Message queue in matter of errors
    SSL_thread->start();

The class will install the following signals and handle the communication over the signals of the class.

{
    m_socketDescriptor=socketDS;							// Copy the tcp/iP descriptor locally
    m_SQLDatabase = SQLDatabase;                             // get the connection from the main process
    m_StateMachineState=NoConnection;
    m_blockSize = 0;                                        // No byte received

    m_sslSocket.setPrivateKey(ApplicationPath+ "../config/" + sPrivatSSLKey);
    m_sslSocket.setLocalCertificate(ApplicationPath+ "../config/" + sLocalSSLCertificate);
    m_sslSocket.setProtocol(QSsl::TlsV1_2);
    m_sslSocket.ignoreSslErrors();

    if ( m_sslSocket.setSocketDescriptor(m_socketDescriptor) == false)	// Connect the socket to the
        {
        m_LastErrorMessage=m_sslSocket.errorString() + tr(": reported from TCP thread");
        emit TCPThreadError(m_LastErrorMessage,1);
        }

    connect(&m_sslSocket,SIGNAL(disconnected(void)), this,SLOT(disconnected(void)));
    connect(&m_sslSocket,SIGNAL(hostFound(void)), this,SLOT(hostFound(void)));
    connect(&m_sslSocket,SIGNAL(connected(void)), this,SLOT(connected(void)));
    typedef void (QSslSocket::* sslErrorsSignal)(const QList<QSslError> &);
    connect(&m_sslSocket, static_cast<sslErrorsSignal>(&QSslSocket::sslErrors),this, &TCPThread::SSLError);
    connect(&m_sslSocket,SIGNAL(readyRead(void)), this,SLOT(readyRead(void)));
    connect(&m_sslSocket,SIGNAL(aboutToClose(void)), this,SLOT(aboutToClose(void)));
    connect(&m_sslSocket,SIGNAL(bytesWritten(qint64)), this,SLOT(bytesWritten(qint64)));
    m_sslSocket.startServerEncryption();
}

It works as long, as the client is only sending information.

But I would to send results back to the client like

    QByteArray					*block;										// Stream Buffer

    block	= new QByteArray;
    QDataStream			outStream(block, QIODevice::ReadWrite);         // just for write only
    outStream.setVersion(QDataStream::Qt_5_4);							// Set the version of stream

    switch( m_ParameterType )
        {
        case			LastPosition:                 // error in command
                            break;
        case			CustomerData:                 // get data from the clients car
                            if ( sendCustomerData(inStream) )
                                {
                                outStream <<  "OK";
                                }
                            else
                                {
                                outStream << "NK";
                                }
                            m_sslSocket.write(*block);											// Send data to the Server
                            m_sslSocket.flush();                                               // send out the data to the server now
                            m_StateMachineState=CommunicationFinish;
                            break;
        case			RecordData:                   // write the information into the database
                            break;
        }

      delete  block;

And during the function "m_sslSocket.write(*block);" I will get the message "QSocketNotifier: Socket notifiers cannot ..."

And hint to solve this ?

Best regards
R.

[SGaist]

Looks like your socket is a member variable of TCPThread which will not be moved to the new thread. You should give it a parent so when calling move to thread it's properly moved along.

[Ritchie]

@SGaist
Hi,

maybe is misunderstood your advise.

I change the parent link of the thread:

    m_task->setParent(0);              << ---add Clear parent information (I guess useless)
    m_task->moveToThread(SSL_thread);

I change the object type from object to object pointer and create the object during creation of the thread.

class TCPThread : public QThread
{
	Q_OBJECT

public:
    TCPThread(int, QSqlDatabase *);                                         // Create a thread object
	~TCPThread();
...
private:
    QSslSocket      *m_sslSocket;                                            // TCP Socket Pointer
...
};

TCPThread::TCPThread(int socketDS,QSqlDatabase *SQLDatabase)
{
    m_sslSocket = new QSslSocket();
...
} 

But I still get the message of the "QSocketNotifier".

What did I misunderstood ?

Best regards
R.

[SGaist]

It's m_sslSocket that you should give a parent to (i.e. add this in the parenthesis).

[Ritchie]

@SGaist
Hi,

I changed it to

this->m_sslSocket->

Edit: I checked as well, only one thread is running.

Same result.
Best regards
R.

[SGaist]

That's not what I suggested.

Here:

m_sslSocket = new QSslSocket(this);

[Ritchie]

Thanks. That solve this problem.
Best regards
R.