Question

In UDP client after executing:

socket.SendTo(data, SendIP);

Why does socket.LocalEndPoint change?

Answer 1

If you never called socket.Bind, then on the first transmission the UDP stack will automatically assign you a local address.

Quote from MSDN:

If you are using a connectionless protocol, you do not need to establish a default remote host with the Connect method prior to calling SendTo. … .You are also not required to call the Bind method, because the underlying service provider will assign the most appropriate local network address and port number.