qmdnsengine on Windows

[denisgottardello]

Hi, I'm using qmdnsengine
on Linux without any problem. On Windows no one device is found.
I have tryied to disable the firewall without any good result.
Does anybody using qmdnsengine on Windows 10?

[cgutman]

I am using it successfully on Windows, macOS, and Linux.

If you have a multi-homed host, you may be having issues because the query is not be sent on the network interface you're expecting. That is fixed by #18

[denisgottardello]

Many thanks for your reply. Does the Bonjour Windows service can generate a conflict? Da: "Cameron Gutman" notifications@github.com A: "nitroshare/qmdnsengine" qmdnsengine@noreply.github.com Cc: "Denis Gottardello" info@denisgottardello.it,"Author" author@noreply.github.com Data: Tue, 03 Mar 2020 00:59:40 -0800 Oggetto: Re: [nitroshare/qmdnsengine] qmdnsengine on Windows (#17) I am using it successfully on Windows, macOS, and Linux. If you have a multi-homed host, you may be having issues because the query is not be sent on the network interface you're expecting. That is fixed by #18 — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[nathan-osman]

"Does the Bonjour Windows service can generate a conflict?"

It shouldn't. QMdnsEngine issues a query before using a hostname to see if another mDNS provider is currently using it. If so, a different hostname is chosen.

[patrickelectric]

I'm building fine under windows

[dlugaz]

If you're interested I tracked the problem with windows (but maybe with other platforms as well, didn't check).
There is a problem with sending queries to multicast on Windows. The bug is also in the multicast sender example in Qt.
On windows for the multicast to work you need to specify setMulticastInterface() for the socket. If not, then sometimes it works, sometimes it doesn't, depends how Windows sees it. Probably it only occurs on machines with multiple interfaces.
Solution:
To properly send multicasts on Windows with multiple interfaces, we need to iterate the interfaces, setMulticastInterface and writeDatagram for each.

void Server::sendMessageToAll(const Message &message)
{
    QByteArray packet;
    toPacket(message, packet);

    const auto interfaces = QNetworkInterface::allInterfaces();
    for (const QNetworkInterface &networkInterface : interfaces) {
        QNetworkInterface::InterfaceFlags iflags = networkInterface.flags();
        if (networkInterface.isValid() &&
            iflags.testFlag(QNetworkInterface::CanMulticast)
            && !iflags.testFlag(QNetworkInterface::IsLoopBack)
            && iflags.testFlag(QNetworkInterface::IsRunning)) {

            QList<QNetworkAddressEntry> addressEntries = networkInterface.addressEntries();
            for (int i = 0; i < addressEntries.length(); i++) {
                QNetworkAddressEntry ae = addressEntries.at(i);

                if (ae.ip().protocol() == QAbstractSocket::IPv4Protocol)
                {
                    d->ipv4Socket.setMulticastInterface(networkInterface);
                    d->ipv4Socket.writeDatagram(packet, MdnsIpv4Address, MdnsPort);
                }
                if (ae.ip().protocol() == QAbstractSocket::IPv6Protocol){
                    d->ipv6Socket.setMulticastInterface(networkInterface);
                    d->ipv6Socket.writeDatagram(packet, MdnsIpv6Address, MdnsPort);
                }

            }
        }
    }

}