the UDP server docs could use some concrete examples

[artificiel]

when setting up for UDP it's not so easy to figure out if things are working or not. some command line boilerplate saves time in "line checking" the communication. such as (tested on macOS12, and linux with openbsd-netcat; adjust the port (9999) to match the --port of the sound command):

echo -n '&i1 0 1 0.5 "this.aif"' | nc -u 127.0.0.1 9999

echo -n "##close##" | nc -u 127.0.0.1 9999

https://github.com/csound/manual/blob/f63c3eef630c45c4eb23cfebf78189217b09b222/overview/server.xml