[zeromq-dev] SUB and PUB sockets on one url over epgm/pgm

[Sergey Zinov]

Hi all,

I encountered problem, while using zeromq with epgm transport.

I have several nodes that should broadcast messages to each other, for 
that purpose each node creates two sockets(one PUB and one SUB) with 
same url. See attachment for sample code(python).

First I tested it on amd64 linux server, and it worked as I expected. 
Each nodes can send and receive messages.
But then I tried it on ARM board, and it worked only 
occasionally(something like 1 of 10 runs). I also tried to run it on 
virtual machines, and sometimes observe such misbehavior there(but it 
works most of the time). So it seems there is some connection between 
performance of machine and this bug.

After some days of tries, I found out, that if I do 
'setsockopt(zmq.SUBSCRIBE, "")' for subscriber socket before I bind 
publisher socket, it works, otherwise described behavior is observed.

With this 'fix' it seems to be working fine. But definitely something is 
wrong here, and I'm not sure how robust this solution is. I'm not really 
sure if it is a bug in zeromq at all - maybe I'm trying to use zmq wrong 
way. Can anybody tell if there is better solution for my case?

Best regards,
Sergey


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