Broadcasts and netmask

[CLOSE Dave]

I wrote:

> I have a Fedora 20 machine which is receiving UDP broadcast packets at
> regular intervals on a high port. No program is presently listening
> for these packets. If I run, "tcpdump -iany port 29531", I see each
> of the packets arriving just as I expect.
>
> But if I then use Ncat as a surrogate for an application, "nc -lup
> 29531", I sometimes don't see anything! Why not? (More details
> below.) What obvious thing am I missing?
> ...

I now understand what is happening on this machine. It's not a bug and 
it's not unique to Fedora. Fedora is enforcing the networking RFC rule 
that general broadcast messages (those to 255.255.255.255) should not 
reach networks other than the one their sender is on. Smaller netmasks 
allowed the machine to be on the sender's network; larger netmasks meant 
that it was not on that network. Issue closed.
-- 
	Dave Close