[OASIS Issue Tracker] Commented: (MQTT-40) Should MQTT Publisher and MQTT Subscriber be differentiated

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    [ http://tools.oasis-open.org/issues/browse/MQTT-40?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33878#action_33878 ] 

Rahul Gupta commented on MQTT-40:
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Hello Nick - Thanks for opening this issue, and yes these changes were made in the recent draft, In the existing specification the client is some time referred as a client and some time referred as publisher or subscriber, and I realized this while working on other MQTT control packet starting from PUBLISH.

e.g from current 3.1 specification  http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html

http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#puback (PUBACK)

A PUBACK message is the response to a PUBLISH message with QoS level 1. A PUBACK message is sent by a server in response to a PUBLISH message from a publishing client, and by a subscriber in response to a PUBLISH message from the server.

http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#pubrec (PUBREC)

A PUBREC message is the response to a PUBLISH message with QoS level 2. It is the second message of the QoS level 2 protocol flow. A PUBREC message is sent by the server in response to a PUBLISH message from a publishing client, or by a subscriber in response to a PUBLISH message from the server.

what I changed in WD-05 
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A PUBACK control packet is the response to a PUBLISH control packet with QoS level 1. A PUBACK packet is sent by a MQTT server in response to a PUBLISH packet from a MQTT publisher, and by a MQTT subscriber in response to a PUBLISH packet from the MQTT server.

A PUBREC control packet is the response to a PUBLISH control packet with QoS level 2. It is the second packet of the QoS level 2 protocol flow. A PUBREC  packet is sent by the MQTT server in response to a PUBLISH packet from a MQTT publisher, or by a MQTT subscriber in response to a PUBLISH packet from the MQTT server.

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For consistency in the specification, I changed the term client at some places to be addressed as a MQTT Publisher or a MQTT subscriber.


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I would still suggest use of MQTT publisher and MQTT subscriber, as it helps getting clarity on which part of the application is originating the contol packet flow. Yes what we could do better is to have a definition of MQTT Server, MQTT publisher, MQTT subscriber added in section 1 of the specification. Here can can document  very clearly about that a MQTT client could be both a MQTT publisher and MQTT subscriber. 

Your thoughts

Kind Regards,
Rahul Gupta 


> Should MQTT Publisher and MQTT Subscriber be differentiated
> -----------------------------------------------------------
>
>                 Key: MQTT-40
>                 URL: http://tools.oasis-open.org/issues/browse/MQTT-40
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>            Reporter: Nick O'Leary
>
> The spec used to talk about MQTT Clients. It now talks about MQTT Publishers and MQTT Subscribers - as if they are completely different things. But ultimately, an MQTT Publisher can subscribe to things and an MQTT Subscriber can publish to things. 
> I'm not sure it is helpful to introduce the idea they are different entities when they are not. It implies you need two different clients if you want to do both pub and sub - a misapprehension we've had to respond to on the mailing list in the past.

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