What happens if PUBREC is not matched to PUBLISH

[Takatoshi Kondo <redboltz@gmail.com>]

Hi,

What is the correct behavior if the client (or broker) receives PUBREC
packet but does not sent corresponding PUBLISH before ?

Here is the scenario

Pre condition. Client hasn't sent PUBLISH QoS2 Packet Identifier 1.
1. The client receives PUBREC Packet Identifier 1, Reason Code 0x00(Success)

I guess it is a protocol error but I couldn't find the description
about that in the spec
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html

I found PUBREL reason code 0x92(Packet Identifier not found).
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901144

Perhaps the client should send PUBREL with reason code 0x92?
PUBCOMP has the same reason code too.
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901154

So the expected behavior is as follows ?

1. The client receives PUBREC Packet Identifier 1, Reason Code 0x00(Success)
2. The client sends PUBREL Packet Identifier 1, Reason Code
0x92(Packet Identifier not found).
3. The broker sends PUBCOMP Packet Identifier 1, Reason Code
0x92(Packet Identifier not found) to the client.

Is that correct?

Or,

1. The client receives PUBREC Packet Identifier 1, Reason Code 0x00(Success)
2. The client sends DISCONNECT Packet with Reason Code 0x82(Protocol error)

Any ideas?

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Thanks,
Takatoshi