qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread

rifky

Hi ,

anyone can help me about qtcpsocket with qthread

Application logs:

Connected client  16
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QTcpSocket(0x7fce4ed06720), parent's thread is QThread(0x7fce4ed02520), current thread is UpdataServerThread(0x7fce4ed82f00)
connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  asd

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  asd

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  asd

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  asd

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  sad

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  sad

Connected client  19
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QTcpSocket(0x7fce4eea12f0), parent's thread is QThread(0x7fce4ed02520), current thread is UpdataServerThread(0x7fce4ee137e0)
connected_client_socket =>  QHash((QHostAddress("::ffff:192.168.200.36"), QTcpSocket(0x7fce4eea12f0)))
connected_client_ip =>  QHash((QHostAddress("::ffff:192.168.200.36"), QTcpSocket(0x7fce4eea12f0)))
QHostAddress("::ffff:192.168.200.36") in :  asdasdas

connected_client_socket =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
connected_client_ip =>  QHash((QHostAddress("::ffff:127.0.0.1"), QTcpSocket(0x7fce4ed06720)))
QHostAddress("::ffff:127.0.0.1") in :  asd

what is wrong about this ?
my code

JonB

@rifky said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

Connected client 19
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QTcpSocket(0x7fce4eea12f0), parent's thread is QThread(0x7fce4ed02520), current thread is UpdataServerThread(0x7fce4ee137e0)

What information are you looking for which is not clear from this error message?

Christian Ehrlicher

You should take a look at QTcpServer::incomingConnection(qintptr)

SGaist

Hi and welcome to devnet,

You are either moving a socket to a different thread or using it directly in that different thread.

In both case it's the wrong thing to do.

Follow @Christian-Ehrlicher advice and move the socket creation in that other thread.

rifky

@SGaist said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

Hi and welcome to devnet,

You are either moving a socket to a different thread or using it directly in that different thread.

In both case it's the wrong thing to do.

Follow @Christian-Ehrlicher advice and move the socket creation in that other thread.

thx for response,
i followed this ,i little bit confused how to implement QThread with qtcpsocket,

can you give me different concept? aside from

server start
server is listening
client connected
thread start

before this i made without thread but when two device is connected and server can receive data from them, but I found anomalies , server can't handle both of them, looks like race condition on readyRead() function.

i guessing with qthread can solve that problem.

JonB

@rifky said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

but I found anomalies , server can't handle both of them, looks like race condition on readyRead() function.

You should rather sort this out.

i guessing with qthread can solve that problem.

I'm guessing that is more likely to create problems than solve them!

Though I may be wrong. If you do want to use threads have you looked at the example https://doc.qt.io/qt-5/qtnetwork-blockingfortuneclient-example.html ? But if it were me I would look at the non-blocking https://doc.qt.io/qt-5/qtnetwork-fortuneserver-example.html. There are no threads there, and it seems much simpler to me. Unless @Christian-Ehrlicher or @SGaist say otherwise....

rifky

@JonB said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

Though I may be wrong. If you do want to use threads have you looked at the example https://doc.qt.io/qt-5/qtnetwork-blockingfortuneclient-example.html ? But if it were me I would look at the non-blocking https://doc.qt.io/qt-5/qtnetwork-fortuneserver-example.html. There are no threads there, and it seems much simpler to me. Unless @Christian-Ehrlicher or @SGaist say otherwise....

I've tried that, i made it into support with multi clients, i put peerAddress with socket pointer in qHash,

before this i made without thread but when two device is connected and server can receive data from them, but I found anomalies , server can't handle both of them, looks like race condition on readyRead() function.

but in this case different with this topic .

anyone can help me to fix my code ?

Christian Ehrlicher

@rifky said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

anyone can help me to fix my code?

which code?

JonB

@Christian-Ehrlicher There is a link to a zip file download at the end of his first post :)

Christian Ehrlicher

You have to create the socket in the run() function as only there the new thread is running. See https://doc.qt.io/qt-5/qthread.html#details

rifky

@Christian-Ehrlicher said in qtcpsocket with qthread QObject: Cannot create children for a parent that is in a different thread:

You have to create the socket in the run() function as only there the new thread is running. See https://doc.qt.io/qt-5/qthread.html#details

its solved , i have tried to create socket in run() function

void UpdataServerThread::run()
{
    updata_socket = new QTcpSocket();
    if (!updata_socket->setSocketDescriptor(socketDescriptor)) {
        emit error(updata_socket->error());
        return;
    }

    connect(updata_socket,SIGNAL(readyRead()),this,SLOT(readyRead()),Qt::QueuedConnection);
    connect(updata_socket,SIGNAL(disconnected()),this,SLOT(disconnected()),Qt::DirectConnection);

    connected_client_socket.insert(updata_socket->peerAddress(),updata_socket);
    qDebug()<<"creating socket ptr";

    updata_socket->write("Welecome Message");
    

    exec();
}

Thanks alot sir ,, i got new another problem with sending/write data on socket maybe i shoud make new topic for this