Qt - Crash when I use a tcp socket to write data if tcp server first closed and then reopened connection

Question

I'm moving my application from Qt 4.7 to Qt 6.3. In Qt 4.7 all works fine. In Qt 6.3 I have some issues when tcp server closes connection, I establish again connection, and I try to write data.

This is the function I use to write to socket:

void NetworkFacility::Write(QTcpSocket& oTCPSocket, const QVariant& oV)
{
    //Controls Socket is valid
    if (oTCPSocket.state() == QAbstractSocket::ConnectedState)
    {
        QByteArray block;                           //ByteArray to serialiaze object
        MyPacket oPacket;                           //Packet to send

        //Set Size of QVariant object
        oPacket.setPacketSize(getQVariantSize(oV));
        //Set QVariant
        oPacket.setTransport(oV);

        //Create stream to write on ByteArray
        QDataStream out(&block, QIODevice::WriteOnly);
        //Sets version
        out.setVersion(QDataStream::Qt_4_7);

        //Serializes
        out << oPacket;
        //TX to socket
        oTCPSocket.write(block);
    }
}

I manage disconnection this way:

void MyClient::remoteNodeDisconnected()
{
  m_pTCPSocket->flush();
  m_pTCPSocket->close();

}

void MyClient::ManagesTCPError(QAbstractSocket::SocketError socketError)
{
    //Clears last packets
    m_pTCPSocket->flush();
}

This is connection portion of code after disconnection:

m_pTCPSocket->connectToHost(m_sIpAddress, m_iIpPort);
//Waits connection
if (m_pTCPSocket->waitForConnected(MSEC_WAIT_FOR_CONNECTION))
{
  //Print connected and exit from while loop
  break;
}

Finally this is the way in which I manage the remote server connecte:

void MyClient::remoteNodeConnected()
{
    //Improve Network latency on this connection
    m_pTCPSocket->setSocketOption(QAbstractSocket::LowDelayOption, 1);
}

The issue is that on the first connection all works fine. If the server disconnects (i.e. I umplugg the server cable in my LAN or I shutdown and restarts the server application) and then connects again the call to:

oTCPSocket.write(block);

in Networkfacility::Write method generates a crash.

Why the write method generates a crash after reconnection?

Answer 1

I fixed the issue by removing completely th oTCPSocket instance.

void MyClient::remoteNodeDisconnected()
{
  m_pTCPSocket->flush();
  m_pTCPSocket->close();
  m_pTCPSocket.deleteLater();
  m_pTCPSocket = 0;
}