[zeromq-dev] A question about FLP

Martin Sustrik sustrik at 250bpm.com
Mon Jul 25 18:09:42 CEST 2011

Hi Matias,

> I am still not too confident about the meaning of XREP/XREQ anyway...
> Perhaps I should re-read the first chapters more carefully ! I am sure
> I am missing something very important.

The theoretical explanation of the hop-by-hop layer (X- sockets) and 
end-to-end layer (non-X sockets) can be found here:


The confusion you are in is caused by the fact that XREP socket 
orginally meant to be a hop-by-hop counterpart of REP socket was reused 
in the guide to route messages to particular destinations in arbitrary 
way (hence "ROUTER" alias)

In new versions of 0MQ the two are already separated: XREP acts as 
hop-by-hop part of request/reply pattern, whereas ROUTER is a generic 
socket type that allows you to experiment with new patterns on top of 0MQ.


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