[zeromq-dev] Multiple connects with a ZMQ_REQ socket appears not to work

Mark e2c at papa.emu.st
Sat Feb 24 01:53:25 CET 2018

> Have a read of the zguide, there should be plenty information of
> various failover patterns: http://zguide.zeromq.org/

Yep, read that. I'm happy with my REQ/REP exchanger pattern now that I
have a better grasp of the underlying behaviour.

As I mentioned previously the docs on REQ/REP state:

   "If no services are available, then any send operation on the
    socket shall block until at least one service becomes available."

but the send() doesn't block in this situation. As you said earlier
the message is queued and sent async with send() returning to the

I also mis-interpreted the docs to imply that when "at least one
service becomes available" that any queued messages would go to that
service, but that's not the case as the round-robin decision is only
made once on the call to send() - not during the async sending

Anyhoo, it's all good now that I know better.


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