Re: IP Multicasting in Classic
Re: IP Multicasting in Classic
- Subject: Re: IP Multicasting in Classic
- From: Joshua Graessley <email@hidden>
- Date: Wed, 20 Nov 2002 13:46:56 -0800
On Wednesday, November 20, 2002, at 03:51 AM, Mark Hunt wrote:
Hi
Hopefully, this a more sensible question than the last one ;-)
I have to provide multicast or broadcast UDP traffic on the local
network (ttl = 1), which has to run in all environments (OS9,
Classic, OSX).
I can set up a multicast UDP receiver which works fine under OS9.2,
but fails in Classic. I don't get any errors, just no data!
I can run it as root, or as a normal user, it makes no difference.
My multicast addresses work out to:
IP = E0,42,88,0E
Enet = 01,00,5E,42,88,0E.
If I change the Ethernet address in the packets to "broadcast",
keeping the IP address the same, it works under Classic, too.
It seems Classic isn't able to add a multicast address to the system,
though it is able to add the multicast IP address.
I've had similar problems adding multicast addresses to an NDRV
socket, problems which were fixed in Jaguar (thanks for that) - is
this a related problem?
Personally, I've no problem with broadcasting my data - there should
be no "uninterested" machines connected to the network while my
system is running - but:
1) Is there a way to make this work properly?
Hmm, filing a bug report would be a good start, but there will be a
large time span between when it gets filed and when a release with the
fix is available.
Is there a reason you can't just run in X native? If you run in X,
you'll also have an opportunity to work with a multi-homed host. You
can specify which interface the multicast is sent on. In the case of a
link-local multicast it probably makes sense to send on every
interface. In the case of a site-local multicast, I'm not sure what you
should do. And of course, in the case of global multicast, you would
only want to send on one interface and you probably want to let the
stack pick the interface.
2) If not, is it really uncool to broadcast (in the Ethernet sense)
multicast UDP datagrams?
Maybe. If you use a subnet broadcast, only IPs on that subnet will
respond to it. If you use the all ones broadcast (255.255.255.255) from
Classic, you might have better luck. I really think you should consider
running in X, not classic.
-josh
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