on startup:
   QNetWorkConfigurationManager *manager = new QNetworkConfigurationManager();

periodical connection check:
   manager->updateConnections();
   QList<QNetworkConfiguration> netlist = manager->allConfigurations(QNetworkConfiguration::Discovered);

   for (auto i=netlist.begin(); i!=netlist.end(); i++)
      switch (i->bearerTypeFamily())
      {
         case QNetworkConfiguration::BearerEthernet:
            qDebug() << "Ethernet discovered";
            break;
         case QNetworkConfiguration::BearerWLAN:
            qDebug() << "WLAN discovered";
            break;
      }