[zeromq-dev] What is the exact issue with enabling MULTICAST_LOOP on ZMQ sockets?

[Marten Feldtmann]

Yes, but now we have to answer theses questions and actually all answers 
are not the way that they are clear in a sense, that programmers might 
know, what that means in real live.

As I understand the situation:

- the reason are mainly due to the Windows platform

- it is not allowed to have a multicast receiver on the same computer 
(including virtual machines ??) when there is a multicast sender and 
both want to talk with each other.

Marten

On 08.06.2013 09:56, Pieter Hintjens wrote:
> If you use MULTICAST_LOOP, you break PGM reliability (Steve explains
> why in that email).
>
> The feature was removed to stop people using it and then asking why
> PGM wasn't working.
>
> -Pieter
>
> On Sat, Jun 8, 2013 at 12:12 AM, Chinmay Nerurkar
> <Chinmay.Nerurkar at fusionts.com>  wrote:
>> We are building a system using ZeroMQ 3.2.3 which will have processes
>> publishing/subscribing on/to multicast channels using PGM (epgm). We would
>> ideally like to have the capability to let a process subscribe to a
>> multicast group where the publishing process resides on the same host. This
>> capability was available through setsockopt() using MULTICAST_LOOP in ZeroMQ
>> v.2.x but has been taken out in the current version. I can put the hooks
>> back into our local ZeroMQ repo to enable MULTICAST_LOOP. However going
>> through some of the dev-list posts like
>> http://article.gmane.org/gmane.network.zeromq.devel/2254/match=multicast it
>> seems like it was taken out for a reason.
>>
>>
>>
>> Can anyone elaborate the reason why MULTICAST_LOOP was taken out of the
>> library and what are the possible side-effects of putting it back in?
>>
>>
>>
>> Thanks.
>>
>>
>>
>> Chinmay
>>
>>
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