[zeromq-dev] Does ZMQ "Over Send" Using OpenPGM

[Martin Sustrik]

Steven,

> That's a lot of groups.  Most hardware and operating systems only
> support 20, plus there is a common problem with groups on the same port.

Ok. So what you are saying the problem happens only if you subscribe to 
more than 20 multicast groups, right?

>   I would follow TIBCO's recommendation and only use unique ports, i.e.
> 239.22.3.1:1001 <http://239.22.3.1:1001>, 239.22.3.1:1002
> <http://239.22.3.1:1002>, etc.

Ok. We have a workaround. However, it would be nice to limit the user in 
such a way he can't possibly get it wrong. Say using a single hard-coded 
multicast group?

> The problem stems because the receiver listens to the port, and then
> adds the multicast group.  Anything received on that port is processed,
> including broadcast traffic.  Whilst on Linux you can bind to a
> multicast group you cannot on other platforms and more importantly for
> PGM you cannot receive unicast traffic and so reliability is not possible.

So AFAIU you get even packets that you haven't subscribed to from the 
raw OS socket.

Would it be a problem to drop the non-matching packets on OpenPGM or 0MQ 
level?

Martin