[zeromq-dev] Problem with REQ/REP and ZMQ_REQ_RELAXED

Luca Boccassi luca.boccassi at gmail.com
Fri Jun 2 12:21:03 CEST 2017

On Fri, 2017-06-02 at 08:02 +0200, Erik Thiele wrote:
> hello
> attached to this mail are two minimum programs.
> i am using debian linux with libzmq3 version 4.0.5.
> compile the programs like this:
> gcc -Wall -Werror server.c -o server -lzmq
> gcc -Wall -Werror client.c -o client -lzmq
> now start them both.
> output of server process:
> receiving first
> sending first
> receiving second
> *** now blocking forever
> output of client process:
> sending first
> sending second
> *** now blocking forever
> If i do not set the options ZMQ_REQ_RELAXED and ZMQ_REQ_CORRELATE in
> the client process, then sending the second time of course fails
> because the state machine is in receive mode. But with this option I
> would expect it does not block, but instead send the next message
> which
> should then be received in the server. instead the client blocks
> forever which I do not understand. What's wrong here?
> Erik


This is most likely due to https://github.com/zeromq/libzmq/issues/1695
 and https://github.com/zeromq/libzmq/issues/1690

They were fixed some time ago but never backported to 4.0.x.

I guess you are on Debian 8 - you can get 4.2.2 which has the fixes
from our repositories on OBS:


Kind regards,
Luca Boccassi
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