Netcat anomaly

[CLOSE Dave]

Rick Stevens wrote:

> Quite odd. Seems to work on my machine. In one window, I did a
>
> nc -lu 29531
>
> and in another:
>
> echo 'Hello there!' | nc -u localhost 29531
>
> and the first window saw the message. Try the same and see if it
> works.

Yes, that works for me. Further, this works when run from a different 
machine on the same network:

echo "UDP broadcast" \
| socat - UDP4-DATAGRAM:255.255.255.255:29531,so-broadcast

Examining the packets as they are captured by tcpdump, both the ones NC 
sees and the ones it doesn't, I don't find anything unusual. No checksum 
or length errors, for example. And comparing them to the one generated 
by socat doesn't reveal any obvious significant difference, either.
-- 
Dave Close