regards a comment that UDP is peerless..i doubt whether this is true.

UDP is connectionless. A UDP sockets can send to any address+port, and it can receive from any address+port. Apparently, one can use PeerAddr to limit from whom packets will be accepted, but that's not a property of the protocol.

UDP is unreliable. It doesn't guarantee notification of delivery failures.

Those are separate (although related) concepts.

the protocol does not guarantee delivery

That goes without saying. No protocols can guarantee delivery. That's impossible. For example, there's no way the protocol can deliver the message if I were to cut the machine's network access.