Hi,I've been working on a Python asyncio-native implementation of ZMTP during the past weeks. So far everything is going great, but as I wrote interoperability tests with pyzmq, I stumbled on a question for which I couldn't find an answer in the various RFCs/documentations.
I've implemented ZMTP 3.1 (http://rfc.zeromq.org/spec:37/) and wish to also support 3.0 (http://rfc.zeromq.org/spec:23/ZMTP/).
From what I understand, the main (only ?) difference in the 3.1 version is the addition of the PING/PONG, SUBSCRIBE/UNSUBSCRIBE commands and endpoint resources.
The SUBSCRIBE/UNSUBSCRIBE part is where I think lies an ambiguity. ZMTP 3.1 removed from the protocol specification the subscription messages in that format:
|subscribe = %x00 short-size %d1 subscription| And replaced those with: |subscribe = command-size %d9 "SUBSCRIBE" subscription |The new RFC makes no reference to the old format whatsoever and so I assume this is because this "old" format is no longer supported in ZMTP 3.1. Put otherwise, the new RFC dictates the use of commands instead of messages and from my understanding, commands are not visible to the application.
This is fine, except the PUBSUB RFC (http://rfc.zeromq.org/spec:29/), in the XSUB/XPUB section does not describe what kind of subscription frame is expected from/to be sent to the application. And since the new protocol uses commands and not frames anymore, there is no obvious way to pass those to/retrieve those from the application layer.
My questions are :- Should an implementation for ZMTP 3.1 still support the "old" subscription format ? I'm asking in the case where the remote peer claims it uses 3.1 as well. - Should an implementation for ZMTP 3.1 convert subscription commands to/from the "old" subscription format in XPUB/XSUB messages ? Is this documented anywhere ?
Thanks ! Julien.
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