Troubleshooting UDP multicast on Windows

Solution 1:

If you have a VirtualBox Host-Only Ethernet Adapter activated on your system that might be the problem, which it was for me, so try disabling it. See https://www.virtualbox.org/ticket/8698.

Solution 2:

You can use a tool like wireshark to watch UDP packets on the troublesome machine. From that you should be able to determine if the UDP packets are even reaching that machine.

Solution 3:

I had similar problems while a Hyper-V virtual ethernet adapter (advertised as vEthernet (default switch)) was active on my machine.

With wireshark I could see the multicast network traffic on my server, but the server application did not respond even though it was registered to the address and port.

So the Answer in this case is: Disable the Hyper-V virtual ethernet adapter if it is enabled.