Re: [mosquitto-dev] Client receives PUBREC and MQTT disconnected

[Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx>]

I think that libmosquitto does not have persistence out of the box, so 
you'd have to implement it yourself.  Someone please correct me if I'm 
wrong.

Ian

On 11/16/2015 08:34 AM, Khitai Pang wrote:
> Yes I'm using QoS 2.  How to persist the inflight message state using 
> libmosquitto?
>
> Regards,
> Khitai
>
> On 2015/11/13 23:17, Ian Craggs wrote:
> > One reason could be that client library does not store MQTT state 
> > across application stops and restarts.
> >
> > If the application is stopped when some MQTT QoS 2 exchanges are 
> > incomplete and the MQTT client library does not persist the inflight 
> > message state (to disk for example), there will be a mismatch between 
> > broker and client state.
> >
> > The Paho Java and C (not embedded) clients do allow you to persist 
> > inflight data to disk, so that when the application is restarted, the 
> > state of inflight MQTT messages is restored, and this situation would 
> > not occur.
> >
> > Ian
> >
> > On 11/13/2015 01:50 AM, Khitai Pang wrote:
> > > Connecting with cleansession=true solved the problem, but all 
> > > offline messages are lost.
> > >
> > > Why is the client receiving a PUBREC that it doesn't know how to 
> > > handle?  What is going wrong here?
> > >
> > > Thanks
> > > Khitai
> > >
> > > On 2015/11/12 18:37, Ian Craggs wrote:
> > > > Have you tried connecting with cleansession=true to clean up the 
> > > > state for that client id?
> > > >
> > > > Ian
> > > >
> > > > On 11/12/2015 08:23 AM, Khitai Pang wrote:
> > > > > Here's what happened:
> > > > >
> > > > > _mosquitto_handle_pubrec handles the received PUBREC, then 
> > > > > _mosquitto_message_out_update updates the message's out status, 
> > > > > but in this function mosq->out_messages is NULL, so 
> > > > > MOSQ_ERR_NOT_FOUND is returned, _mosquitto_loop_rc_handle handles 
> > > > > the response code, since it's an error, finally 
> > > > > _mosquitto_socket_close(mosq) is called.
> > > > >
> > > > > Regards
> > > > > Khitai
> > > > >
> > > > > On 2015/11/12 15:08, Khitai Pang wrote:
> > > > > > Got rc=6 in the ondisconenct callback.
> > > > > >
> > > > > > Regards
> > > > > > Khitai
> > > > > >
> > > > > > On 2015/11/12 14:43, Khitai Pang wrote:
> > > > > > > Hi,
> > > > > > >
> > > > > > > I am having problem with a particular MQTT client ID. When a 
> > > > > > > client connects to Mosquitto using this ID, it immediately 
> > > > > > > receives a PUBREC from the broker and then MQTT get disconnected:
> > > > > > >
> > > > > > > 2015-11-10 20:35:21.827 mqtt-test[58102:737651] === MQTT 
> > > > > > > connected===
> > > > > > > 2015-11-10 20:35:22.329 mqtt-test[58102:737651] mosquitto log : 
> > > > > > > Client 362f23d0-8906-11e5-99da-005056355a83 received PUBREC 
> > > > > > > (Mid: 58)
> > > > > > > 2015-11-10 20:35:22.454 mqtt-test[58102:737651] === MQTT 
> > > > > > > disconnected===
> > > > > > >
> > > > > > > Log on the broker side:
> > > > > > >
> > > > > > > ...
> > > > > > > testhost mosquitto[4911]: New client connected from ... as 
> > > > > > > 362f23d0-8906-11e5-99da-005056355a83 (c0, k120).
> > > > > > > testhost mosquitto[4911]: Socket error on client 
> > > > > > > 362f23d0-8906-11e5-99da-005056355a83, disconnecting.
> > > > > > > ...
> > > > > > >
> > > > > > > The broker is mosquitto 1.3.5.  The client uses libmosquitto in 
> > > > > > > mosquitto 1.4.4.
> > > > > > >
> > > > > > > Any help is appreciated.
> > > > > > >
> > > > > > >
> > > > > > > Regards,
> > > > > > > Khitai
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--
Ian Craggs
icraggs@xxxxxxxxxx                 IBM United Kingdom
Paho Project Lead; Committer on Mosquitto