UDP Broadcast Address 127.255.255.255

Question

I have seen some say UDPSocket Broadcast to 127.255.255.255.

1)What so special about this

   127.*.*.*` network?

2)If I have client systems that are not in this 127.*.*.* network and I don't know what network they are on then what broadcast address I should use so the client can receive the message.

3)During the UDP Broadcast, I guess the Server address is Not important because it's a connectionless transmission?

Answer 1

1. 127.0.0.0/8 is a special address block that's reserved for loopback to the same machine, it should never be the address of a real network interface. In particular, 127.0.0.1 is the default localhost address (look at the lo0 interface on a Unix machine).

2. You should never have client systems in the 127/8 network. I don't think 127.255.255.255 could be intended to send to the network, it should only be for sending to the local machine.

3. If necessary, the client can get the server address when it receives the response. It can then use this to keep communicating with that server.