Problem to bind a UDP socket.

[jsulm]

@jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

[jenya7]

@KroMignon said in Problem to bind a UDP socket.:

@jenya7 said in Problem to bind a UDP socket.:

result = socket->bind(QHostAddress(local_ip), local_port);
QString err = socket->errorString();
result = socket->error();

This code do not make sense to me, you have to check if operation was not successful before trying to find an error!
There is no error code "Success" in QAbstractSocket::SocketError (cf. https://doc.qt.io/qt-5/qabstractsocket.html#SocketError-enum).

Please review your code.

OK.

int UDP::Start(QString local_ip, quint16 local_port, QString *err_str)
{
    int result;

    //socket->reset();
    //socket->setProxy(QNetworkProxy::NoProxy);

    result = socket->bind(QHostAddress::Any, local_port);
    //result = socket->bind(QHostAddress(local_ip), local_port);

    if (result != 0)
    {
        *err_str = socket->errorString();
         result = socket->error();
    }

    return result;
}

So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
Should I trust to a returned result?

[jenya7]

@jsulm said in Problem to bind a UDP socket.:

@jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

can not do that.
it's UDP socket, not Abstract socket. it has no errorOccurred signal.

QUdpSocket *socket;

[KroMignon]

@jenya7 said in Problem to bind a UDP socket.:

So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
Should I trust to a returned result?

Please take time to read a little bit of documentation. This will save you many of your time. It is very easy with Qt Creator, you only have to hit F1 to get help for a function!

QUdpSocket::bind() (cf. https://doc.qt.io/qt-5/qabstractsocket.html#bind) will return a boolean:

• true: success
• false: error

[Christian Ehrlicher]

@jenya7 said in Problem to bind a UDP socket.:

it's UDP socket, not Abstract socket.

QUdpSocket derives from QAbstractSocket...

udp_1.Start("192.168.3.40", 8001, &err_str);

You call Start() with an IP which you computer doesn't have according your ipconfig output above. This can't work. Also 172.16.1.118 is not your IP.

[KroMignon]

@jenya7 said in Problem to bind a UDP socket.:

it's UDP socket, not Abstract socket. it has no errorOccurred signal.

QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
Do you know what subclassing means?

[jenya7]

@KroMignon said in Problem to bind a UDP socket.:

@jenya7 said in Problem to bind a UDP socket.:

it's UDP socket, not Abstract socket. it has no errorOccurred signal.

QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
Do you know what subclassing means?

QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);

void UDP::SocketError(QAbstractSocket::SocketError socketError)
{
    qDebug() << "Socket Error: " << socketError;
}

I get
error: no matching member function for call to 'connect'

[Christian Ehrlicher]

@jenya7 said in Problem to bind a UDP socket.:

QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);

And again to lazy to hit 'F1': https://doc.qt.io/qt-5/qabstractsocket-obsolete.html#error-1

Note: Signal error is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(abstractSocket, QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error),
    [=](QAbstractSocket::SocketError socketError){ /* ... */ });

Also this signal is deprecated - use errorOccurred() if possible (since Qt5.15)

[KroMignon]

@jenya7 said in Problem to bind a UDP socket.:

QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);

This signal is called errorOccurred() and not error()

[EDIT] errorOccurred() has been added with Qt 5.15, if you are using an older Qt version, use code suggested by @Christian-Ehrlicher

[jenya7]

@KroMignon said in Problem to bind a UDP socket.:

@jenya7 said in Problem to bind a UDP socket.:

So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
Should I trust to a returned result?

Please take time to read a little bit of documentation. This will save you many of your time. It is very easy with Qt Creator, you only have to hit F1 to get help for a function!

QUdpSocket::bind() (cf. https://doc.qt.io/qt-5/qabstractsocket.html#bind) will return a boolean:

• true: success
• false: error

oops. sorry.