Details
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Bug
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Resolution: Won't Do
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P2: Important
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None
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5.15.3
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None
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Windows UWP x64
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WinRT
Description
This problem causes app to not being able to join multicast groups on UWP platform.
I printed the flags for network interfaces and they show that no interface has CanMulticast flag set though those network interfaces can multicast.
So I believe that is the reason, why socket fails to join multicast group if no checks made.
The same code runs just fine on Windows (non-UWP), Ubuntu, Android, iOS.
I run this sample on Windows under Virtualbox. But I also tested in real Windows x64 machine and Windows x64 IoT tablet.
I'll post my code, but QT multicastreceiver example can be used to check, as it has the same issue.
if (m_multicastSocket->state() != QAbstractSocket::BoundState) {
if (!m_multicastSocket->bind(QHostAddress::AnyIPv4, MULTICAST_HELLO_PORT, QAbstractSocket::ShareAddress | QAbstractSocket::ReuseAddressHint)) {
LOGW << "Error: Failed to bind multicast socket!";
return;
}
else
LOGD << "Successfully bound to multicast HELLO port:" << MULTICAST_HELLO_PORT;
const QString& ifName = ClientNetworkManager::instance().desiredInterfaceName();
if (!ifName.isEmpty())
m_multicastSocket->setMulticastInterface(QNetworkInterface::interfaceFromName(ifName));
for (const auto& i : QNetworkInterface::allInterfaces()) {
LOGW << "Interface:" << i.name() << "loopback:" << bool(i.flags() & QNetworkInterface::IsLoopBack)
<< "\nrunning:" << bool(i.flags() & QNetworkInterface::IsRunning)
<< "\nmulticast:" <<bool(i.flags() & QNetworkInterface::CanMulticast)
<< "\naddress is empty:" << i.addressEntries().isEmpty();
if (!(i.flags() & QNetworkInterface::IsLoopBack)
&& (i.flags() & QNetworkInterface::IsRunning)
&& (i.flags() & QNetworkInterface::CanMulticast)
&& (!i.addressEntries().isEmpty()))
{
if (!m_multicastSocket->joinMulticastGroup(QHostAddress(MULTICAST_HELLO_GROUP), i)) {
LOGW << "Error: Joining multicast group failed on interface" << i.name() << i.humanReadableName() << i.hardwareAddress() << "with error:" << m_multicastSocket->errorString();
}
else
LOGW << "Successfully joined multicast group on interface" << i.name() << i.humanReadableName() << i.hardwareAddress();
}
}
}
The log output is:
Successfully bound to multicast HELLO port: 55555 Interface: "{76FCD10B-5F45-4155-9C42-31960A66A6E2}" loopback: false running: true multicast: false address is empty: false Interface: "{76FCD10B-5F45-4155-9C42-31960A66A6E2}" loopback: false running: true multicast: false address is empty: true
The log for the same app rebuilt as normal Windows app:
Successfully bound to multicast HELLO port: 55555 Interface: "ethernet_32771" loopback: false running: true multicast: true address is empty: false Successfully joined multicast group on interface "ethernet_32771" "vEthernet (Default Switch) 2" "50:15:5D:D0:DB:77" Interface: "ethernet_32774" loopback: false running: true multicast: true address is empty: false Successfully joined multicast group on interface "ethernet_32774" "Ethernet 2" "08:00:27:DC:00:5D" Interface: "loopback_0" loopback: true running: true multicast: true address is empty: false Interface: "ethernet_32780" loopback: false running: true multicast: true address is empty: false Successfully joined multicast group on interface "ethernet_32780" "vEthernet (nat) 2" "00:15:5D:C8:5C:2A"