Q:

What happens when two clients send UDP packets to a Socket

Lets assume Host X has a UDP Socket running on Port 1337.
Now Host Y and Z both send a UDP Packet to port 1337 of Host X.
Are the packets going to be de-muxed?

A:

UDP is a transfer protocol with no guarantees of delivery and doesn't have much of an implementation.
When both host Y an Z send a UDP packet to port 1337, and assuming both packets arrive, the application listening on port 1337 decides what happens with those packages. The application can choose which packet to demux, to demux both or to demux neither.
Hope this clears things up

