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

[Pieter Hintjens]

If anyone really wants the MULTICAST_LOOP functionality, we can add it
back and try to make the documentation and defaults clear...

On Sat, Jun 8, 2013 at 11:25 AM, Marten Feldtmann
<itlists at schrievkrom.de> wrote:
> 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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>>>
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