Get local IP address in Qt

Use QNetworkInterface::allAddresses()

const QHostAddress &localhost = QHostAddress(QHostAddress::LocalHost);
for (const QHostAddress &address: QNetworkInterface::allAddresses()) {
    if (address.protocol() == QAbstractSocket::IPv4Protocol && address != localhost)
         qDebug() << address.toString();
}

QNetworkInterface::allAddresses() will give you the network addresses. You can then filter the results to IPv4 addresses that are not loopback addresses:

QList<QHostAddress> list = QNetworkInterface::allAddresses();

 for(int nIter=0; nIter<list.count(); nIter++)

  {
      if(!list[nIter].isLoopback())
          if (list[nIter].protocol() == QAbstractSocket::IPv4Protocol )
        qDebug() << list[nIter].toString();

  }

QNetworkInterface returns lots of addresses. you must filter them, to get desirable result:

foreach (const QNetworkInterface &netInterface, QNetworkInterface::allInterfaces()) {
    QNetworkInterface::InterfaceFlags flags = netInterface.flags();
    if( (bool)(flags & QNetworkInterface::IsRunning) && !(bool)(flags & QNetworkInterface::IsLoopBack)){
        foreach (const QNetworkAddressEntry &address, netInterface.addressEntries()) {
            if(address.ip().protocol() == QAbstractSocket::IPv4Protocol)
                qDebug() << address.ip().toString();
        }
    }
}

If you require more information than just IP addresses (like the subnet), you have to iterate over all the interfaces.

QList<QNetworkInterface> allInterfaces = QNetworkInterface::allInterfaces();
QNetworkInterface eth;

foreach(eth, allInterfaces) {
    QList<QNetworkAddressEntry> allEntries = eth.addressEntries();
    QNetworkAddressEntry entry;
    foreach (entry, allEntries) {
        qDebug() << entry.ip().toString() << "/" << entry.netmask().toString();
    }
}