Re: [mqtt-comment] Inconsistent reason code between SUBACK and UNSUBACK

[Jonathan Levell <LEVELL@uk.ibm.com>]

Hi,

If the broker doesn't support wildcards
or shared subscriptions, the subscription would not have been successfully
created in the first place.

If the client tries to perform an unsubscribe
for a wildcard/shared subscription that had previously failed to be
created, I think the appropriate return
code would be 17 (0x11) No Subscription existed.

Jon

Jon Levell
Project Lead for Eclipse Amlen
Architect for Watson IoT Platform Connect




From:      
 "Takatoshi Kondo"
<redboltz@gmail.com>
To:      
 mqtt-comment@lists.oasis-open.org
Date:      
 15/07/2021 05:40
Subject:    
   [EXTERNAL] [mqtt-comment]
Inconsistent reason code between SUBACK and UNSUBACK
Sent by:    
   <mqtt-comment@lists.oasis-open.org>

---

Hi,

According to

3.9.3 SUBACK Payload
Table 3‑8 - Subscribe Reason Codes
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901178

SUBACK reason code has the following values:

158 Shared Subscriptions not supported
161 Subscription Identifiers not supported
162 Wildcard Subscriptions not supported

On the contrary, UNSUBACK doesn't have them.

3.11.3 UNSUBACK Payload
Table 3‑9 - Unsubscribe Reason Codes
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901194

It is reasonable that UNSUBACK doesn't have "Subscription Identifiers
not supported" because UNSUBSCRIBE cannot have Subscription Identifier
property.

However, UNSUBSCRIBE could have $shhare/sharename, and wildcards. So
UNSUBACK should have the following reason code:

158 Shared Subscriptions not supported
162 Wildcard Subscriptions not supported

Any ideas?

----
Thanks,
Takatoshi

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