UWP DatagramSocket Multicast

Question

I managed to make a simple application that sends and receives data from a multicast group. If I open 2 instance of the application (2 different .sln files with the same code) I

Answer 1

So in conclusion, how can I achieve, no matter when (not within 5 seconds) some of the clients sends a message, all of the other clients get it?

It seems like that this issue has been fixed in the latest Windows RS1(Build 14393) OS, here is the screenshot(Gif):

You may need to upgrade the OS to solve it.