QtMqtt subscription problem

PhysicsX

Hello

I interested in qtmqtt library.
I simply compiled and make it ready to use for raspberry pi.

When try to write simple subscription appliocation it will fail. Like:

        QMqttClient *m_client;
        m_client = new QMqttClient();
        m_client->setHostname(QString("iot.reyax.com"));
        m_client->setPort(1883);
        m_client->setUsername(QString("zFtbPwRwxE"));
        m_client->setPassword(QString("GhMshMhWG9"));

        auto subscription = m_client->subscribe(QString("api/command/28/#"), 0);
           if (!subscription) {
               qDebug()<<"Can not subscribe to topic";

But when I put two buttons (first one is responsible to set hostname, port vs and the second one is respobsible for subscription) then everthing will work interestingly.

I put some delay, sleep before m_client->subscribe but it do not work.

I use for the cloud -> http://reyax.com/wp-content/uploads/2017/10/RYC1001_Application_note_Windows_MQTT.FX_.pdf you can try the password and other related stuff for connection from this pdf.

Simply I need to make subscription available in the simple namespace. Why it is not working when I try to run like this ( above code snippet )
my qt version 5.14.2

SGaist

Hi,

You should do some error checking with QMqttClient::error.

PhysicsX

Hi SGaist

Thanks for the answer.

Could you provide any example ?
I only set some strings. Why should I check some errors after this ?

Thank you.

SGaist

Because you are then subscribing which will trigger network connection which might fail for some reasons that might be explained through that property.