[zeromq-dev] ZMTP query

Chris Laws clawsicus at gmail.com
Wed Jul 2 12:30:26 CEST 2014

I am playing around with ZMTP for 'reasons'. I have implemented my own ZMTP
client and I observe that when I connect to a ROUTER socket (which is a
simple CZMQ server) and progress through the greeting and NULL handshake,
the router is sending my client an identity property which I am not

In the worked example section of 37/ZMTP <http://rfc.zeromq.org/spec:37>
there is text that states:

The server validates the socket type, accepts it, and replies with a READY
command that contains only the Socket-Type property (ROUTER sockets do not
send an identity):

| %x04 | 28 |
| %x05 | R | E | A | D | Y |
| 11 | S | o | c | k | e | t | - | T | y | p | e |
| %x00 | %x00 | %x00 | %x06 | R | O | U | T | E | R |

In my case, after the greeting I see a NULL security handshake command like


This isn't stopping me from doing anything. It's just a query stemming from
what I'm seeing not aligning with my interpretation of the ZMTP
specification page.

>From a quick look through the libzmq code (null_mechanism.cpp) it seems
that the Identity property is explicitly added for REQ, DEALER and ROUTER

Should the 37/ZMTP spec be updated?

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