QTcpSocket connecting even tho no server?

[SPlatten]

@J-Hilk , thank you, I've changed the code to:

void clsMsgSender::onStartService() {
qdbg() << mpsckClient->state();
    if ( mpsckClient->state() != QAbstractSocket::ConnectedState ) {
    //Change connection interval to regular connection time period for reconnects
        mptmrConnect->setInterval(clsMsgSender::mscuint16ConnectTimer);
    //Get local IP address
        QString strIP = clsMsgSender::strGetLocalIP();
        qdbg() << "Connecting to: " << strIP << ":" << muint16Port;
    //Connect to the Application
        mpsckClient->connectToHost(strIP, muint16Port);
    }
    if ( clsMsgSender::mspThread == nullptr ) {
        clsMsgSender::mspThread = new QThread;
        moveToThread(clsMsgSender::mspThread);
        QObject::connect(clsMsgSender::mspThread, &QThread::started
                    ,this, &clsMsgSender::run);
        QObject::connect(this, &clsMsgSender::finished
                    ,clsMsgSender::mspThread, &QThread::quit);
    }
    if ( mqueMsgsOut.size() > 0 && clsMsgSender::mspThread != nullptr ) {
        clsMsgSender::mspThread->start();
    }
}

I've also added a connection to:

QObject::connect(mpsckClient, &QTcpSocket::hostFound
                    ,this, &clsMsgSender::onHostFound);

In my onHostFound slot:

void clsMsgSender::onHostFound() {
   qdbg() << "Host Found!";
}

From the Application Output I can see lots of Host Found! messages, is this normal when the IP:Port doesn't have anything listening to it?

[ollarch]

@SPlatten said in QTcpSocket connecting even tho no server?:

From the Application Output I can see lots of Host Found! messages, is this normal when the IP:Port doesn't have anything listening to it?

But the host if found. The problem will be if the localhost is not found. One thing is that it found the host and the other thing is that there is some process linstening on the port.

[SPlatten]

@ollarch , the IP exists on the system, but there is no application running listening for connection, nothing is using that port.

[KroMignon]

@SPlatten said in QTcpSocket connecting even tho no server?:

From the Application Output I can see lots of Host Found! messages, is this normal when the IP:Port doesn't have anything listening to it?

Why do you never read documentation before asking what already describe in documentation?
Have you tried to read connectToHost() documentation (hint: just hit F1 key in Qt Creator):

Attempts to make a connection to hostName on the given port. The protocol parameter can be used to specify which network protocol to use (eg. IPv4 or IPv6).

The socket is opened in the given openMode and first enters HostLookupState, then performs a host name lookup of hostName. If the lookup succeeds, hostFound() is emitted and QAbstractSocket enters ConnectingState. It then attempts to connect to the address or addresses returned by the lookup. Finally, if a connection is established, QAbstractSocket enters ConnectedState and emits connected().

At any point, the socket can emit errorOccurred() to signal that an error occurred.

hostName may be an IP address in string form (e.g., "43.195.83.32"), or it may be a host name (e.g., "example.com"). QAbstractSocket will do a lookup only if required. port is in native byte order.

As you could read:

• the socket is opened, so QTcpSocket::isOpen() will return true
• hostname lookup is started ==> hostFound() is emitted on success
• on success, connection is started

It is so hard to read documentation????

[J.Hilk]

@SPlatten do you call connectToHost multiple times ? IIRC each connectTohost call may emit a HostFound signal

[SPlatten]

@J-Hilk I do call every 5 seconds.

[ollarch]

@SPlatten said in QTcpSocket connecting even tho no server?:

@ollarch , the IP exists on the system, but there is no application running listening for connection, nothing is using that port.

So, the host is found.
As @KroMignon has told you a lot of times is to read the documentation.
It seems that you write some code, test, and if it fails you start writing a new thread in the forum.
Yes, I know that you have a lot work to do but this also applies to us.

[SPlatten]

@ollarch, I have read the documentation, and nowhere does it say that the hostFound signal is issue when the IP is found regardless of the port!

The IP and Port combine make the address, the IP itself is no indication that there is anything to connect to, not if there is nothing using the specified port. And this information is not documented, hence my question.

[Christian Ehrlicher]

@SPlatten said in QTcpSocket connecting even tho no server?:

and nowhere does it say that the hostFound signal is issue when the IP is found regardless of the port!

Sorry but the error is called 'HostNotFound' - not 'Can not connect to host and port'...

[SPlatten]

@KroMignon , I didn't say I never read the documentation, that's your inference and on this occasion I find that the documentation is not detailed enough. An address has two parts, the IP and the port.

[KroMignon]

@SPlatten said in QTcpSocket connecting even tho no server?:

I find that the documentation is not detailed enough. An address has two parts, the IP and the port.

It is written in documentation:
The socket is opened in the given openMode and first enters HostLookupState, then performs a host name lookup of hostName. If the lookup succeeds, hostFound() is emitted

=> host name lookup, this is done before connection starts, so no need of TCP port.

This is very explicitly described in documentation.

[JonB]

@SPlatten
I don't want to get into an argument, but it does say that.

https://doc.qt.io/qt-5/qabstractsocket.html#hostFound :

This signal is emitted after connectToHost() has been called and the host lookup has succeeded.

https://doc.qt.io/qt-5/qabstractsocket.html#connectToHost :

The socket is opened in the given openMode and first enters HostLookupState, then performs a host name lookup of hostName. If the lookup succeeds, hostFound() is emitted and QAbstractSocket enters ConnectingState. It then attempts to connect to the address or addresses returned by the lookup. Finally, if a connection is established, QAbstractSocket enters ConnectedState and emits connected().

So, as it says, hostFound signal is emitted on finding the host IP address. It does what it says on the packet, i.e. it's just a host lookup, by name or IP address, and tells you the host does exist.

Connecting on the port comes after that, and of course may succeed or fail separately.

Anyway, there it is, that's how it works.

[SPlatten]

@JonB , as I said previously the IP is just part of the address, the port completes the address, when you establish the connection the port is optional, but if supplied then it should be used because connecting to address and address:port are very different.

[Christian Ehrlicher]

@SPlatten said in QTcpSocket connecting even tho no server?:

address:port

This is wrong. It's host:port !

[SPlatten]

@Christian-Ehrlicher , are you being piccy?

[Christian Ehrlicher]

@SPlatten said in QTcpSocket connecting even tho no server?:

are you being piccy?

No, but your assumptions are wrong because of this wrong definition.

[JonB]

@SPlatten
Sorry, Simon, you're incorrect. I did try to explain. I do know what IP addresses vs ports are. I was just pointing out, politely, that Qt's hostFound is emitted on host found, not on port is listening/connected. Anyways, it's not worth arguing about, we were just talking about how Qt documents what it is that it does when.

[KroMignon]

@SPlatten said in QTcpSocket connecting even tho no server?:

as I said previously the IP is just part of the address, the port completes the address, when you establish the connection the port is optional, but if supplied then it should be used because connecting to address and address:port are very different.

Your are mixing up definitions:

• Hostname is IP address or a name (like "www.qt.com")
• portnum is the TCP port (number between 0 and 65534).
• combination of hostname and TCP port is an Endpoint
• a TCP connection is defined as a combination of 2 endpoints, the local endpoint and the remote endpoint

[Darta]

I have the same issue no listening server at the adress port but it's connecting anyway:

bool Client::bindTo(QString adress, quint16 port)
{
    QHostAddress adressToCo;
    if (adressToCo.setAddress(adress) == true)
    {
        m_socket = new QTcpSocket;
        if (!m_socket->bind(adressToCo, port)) {
            m_errorMsg = "Cannot connect to " + adress;
            qDebug() << "Cannot connect to " + adress;
        }
    }
    else {
        m_errorMsg = "Wrong IP address.";
        qDebug() << "Wrong IP address: " + adress;
        return false;
    }
    qDebug() << "Bind corectly to " + adress;
    return true;
}

bool Client::connectTo(QString adress, quint16 port)
{
    QHostAddress adressToCo;
    adressToCo.setAddress(adress);
    QObject::connect(m_socket, &QTcpSocket::readyRead, [=] {
        QString msg = m_socket->readAll();
        emit msgRcvd(msg);
    });
    m_socket->connectToHost(adressToCo, port);
    if (!m_socket->waitForConnected(5000)) {
        m_errorMsg = m_socket->errorString();
        qDebug() << "Error socket:" << m_socket->errorString();
        return false;
    }
    else if(m_socket->state() != QAbstractSocket::ConnectedState) {
        m_errorMsg = m_socket->errorString();
        qDebug() << "Error socket:" << m_socket->errorString();
        return false;
    }
    qDebug() << "Connect corectly to " + adress;
    m_socket->write("I'm writing a message that will be lost somewhere over the rainbow");
    return true;
}

I gave the same adress port to both functions :
Adress: "192.168.1.42" Port: 58513

Regardless the port number I put in,
I also could set the adress to "127.0.0.1" it is always the same issue:
the client is connected.

Output of software:

Adress: "192.168.1.42" Port: 58513
"Bind corectly to 192.168.1.42"
"Connect corectly to 192.168.1.42"
Client connected: true

to get the final line i'm using :

    m_socket->state() == QAbstractSocket::ConnectedState ? true : false;

So everytimes the QTcpSocket connect itself to my adress regardless of my port...
When I launch my server, the server doesn't have any connection either

[JonB]

@Darta said in QTcpSocket connecting even tho no server?:

I have the same issue no listening server at the adress port but it's connecting anyway:

"Bind corectly to 192.168.1.42"

"Connect corectly to 192.168.1.42"

I don't understand. Your bindTo() does the listening, the connectTo() connects to that, they are both using the same port number, your program is acting as both client and server. That's how it looks to me, so what's the problem?