Re: [mosquitto-dev] mosquitto.conf - subscribed topics using MQTT protoc

[BinduRao <bindu@xxxxxxxxxxxxx>]

Hi Roger,

Many thanks for providing the video to use as a reference. By setting 
the value of persistence to 'true' at the broker configuration, the 
subscribed topics are retained.
Here are few questions w.r.t the configuration and behaviour:
- W.r.t mosquitto.conf available the default protocols are only set to 3 
& 3.1.1. In the shared m.conf, the configuration of the protocol is not 
available. Is this ok? Shouldn't the protocol be explicitly set to 
support 3.1.1 & 5?

- Use of persistence on broker and clean start/clean session - I use 
paho_mqtt_c client to communicate with mosquitto. If 'persistence = 
true' in m.conf, is the value set from the client ignored? I observe 
that when 'persistence' is set to true, setting clean start = true/false 
doesn't change the behaviour. The subscribers are always stored. Is this 
expected?

Thanks,
Bindu
On 21/04/21 1:52 am, Roger Light wrote:
> Hi Bindu,
>
> I've tested out this scenario and as far as I can tell it works as expected.
>
> I've recorded a short asciicast of me doing that test so you can try
> to investigate where the difference is:
> https://asciinema.org/a/ICpJtr4cOPDxxpgYLIlVnjPSj
>
> If what you are doing is different, could you please describe what
> exactly is different?
>
> Regards,
>
> Roger
>
> On Tue, 20 Apr 2021 at 17:38, Bindu Rao <bindu@xxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > I am using mosquitto broker with paho_mqtt client. I notice a problem in
> > the following scenario:
> > Usecase:
> > - MQTT Protocol set to 5
> > - Clean start = false and session expiry interval set to 30 secs
> >
> > I configure the client for publication and subscription on a topic.
> > Terminate and restart mosquitto.
> >
> > Expected behaviour:
> > - Should be able to receive messages on a subscribed topics after
> > reconnection.
> > Actual behaviour:
> > - Session not remembered, hence need to be resubscribed even when clean
> > the start is set to false by the client.
> > I am using mosquitto - 2.0.10. The behaviour is perfectly ok when used
> > with protocol 3.1.1.
> > What configuration variables should be set in mosquitto.conf to get this
> > working? Could you please provide inputs?
> > Please note, that this works fine when I use other mqtt brokers.
> >
> > Thanks,
> > Bindu
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