[zeromq-dev] empty packet if REQ

[Ilja Golshtein]

Martin,

thank you for shedding some light on this.
Without it examples one can see e.g. in your "A multithreaded server in 10 mins"
are slightly mysterious.

To be honest I haven't get why XREQ don't put null packet though.

13.08.10, 14:54, "Martin Sustrik" <sustrik at 250bpm.com>:

> Ilja,
>  
>  > Could you please describe in more detailed way in which cases these extra identities are appended.
>  > 
>  > 
>  > (1)                  (2)                (3)
>  > 
>  > REQ-send                          XREP-recv
>  > 
>  > ID1                                     ID2
>  > null                                     ID1
>  > payload                               null
>  >                                           payload
>  
>  
>  Actually, the identity as added by XREP socket so it looks like this:
>  
>  Request:
>  
>  payload ---> (REQ) --- null|payload --> (XREP) ---  id1|null|payload 
>  ---> (XREQ) --- id1|null|payload ---> (REP) ---> payload
>  
>  Reply:
>  
>  payload ---> (REP) --- id1|null|payload ---> (XREQ) --- id1|null|payload 
>  ---> (XREP) ---> null|payload ---> (REQ) ---> payload
>  
>  > The question is what should be done at (2) in 0mq API terms to have extra identity added.
>  
>  As already said XREP is the socket resposible for adding removing 
>  identities. So it adds identity of the peer to the request and sends it 
>  firther.
>  
>  When it gets the reply. It chops one identity from the backtrace stack 
>  and uses it to route the reply to the right peer.
>  
>  Martin
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>  
>  

-- 
Best regards,
Ilja Golshtein.