// Qt may provide us with an IPv4-mapped IPv6 address, so
// convert it to an explicit IPv4 if it's a mapped IPv4.
if (sender.protocol() == QAbstractSocket::IPv6Protocol)
{
    bool isMapped = false;
    quint32 ipv4 = sender.toIPv4Address(&isMapped);
    if (isMapped)
    {
        sender = QHostAddress(ipv4);
    }
}