[lug] OT: UDP multicast question

D. Stimits stimits at idcomm.com
Fri Apr 5 15:41:58 MST 2002

"Scott A. Herod" wrote:
> Hello,
>   I'm not much of a network programmer so this may be an
> obvious question.  Can I have multiple processes on a single
> machine listening to a local udp multicast?  This is with IPv4,
> but would IPv6 make a difference?  (MySQL doesn't implement
> triggers and I need to tell several processes when a table
> changes.)

I wouldn't try it with IPv4, don't know if IPv6 is different. As soon as
a process reads the buffer you can expect the data to go away, or else
for it to be marked as empty. I'd guess the same is true for IPv6 but
don't know. You would probably be better off creating a surrogate daemon
that does the listening, has either an update buffer or a notification
of change, and allows multiple subscribers; it would publish to anything
subscribed. You could go as far as to offer an ability to subscribe to
particular sql servers, databases within servers, tables within
databases, so on. Then you are totally isolated from the type of sql
server. Lots of fun things you can do with it, depending on what you
want as the end goal, but I doubt you'll get anything other than
surprises if you have multiple processes trying to listen to the same
UDP socket and expecting them to get the same information.

D. Stimits, stimits at idcomm.com

> Thanks,
> Scott
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