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MQSeries.net Forum IndexIBM MQ Telemetry / Low Latency Messaging / EveryplaceWMQ7.5, MQTT : Unable to publish.

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Cogito-Ergo-Sum
PostPosted: Mon Aug 27, 2012 10:47 am Post subject: WMQ7.5, MQTT : Unable to publish. Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

Hi,
I hope, this is the right place to ask questions on MQTT in WMQ7.5.

I downloaded the Linux x86-64 bit version of WMQ7.5, installed it on my Ubuntu 12.04 64-bit OS.

After setting up the telemetry channels, I tried publishing from mosquitto_pub command, the MQTT client utility built in the MQ Explorer and the IA92 SupportPac. Everywhere, the connection happens successfully. But, as soon as I publish on any topic, I get a message as connection lost.

What could be the reason ?
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mqjeff
PostPosted: Mon Aug 27, 2012 10:53 am Post subject: Reply with quote

Grand Master

Joined: 25 Jun 2008
Posts: 17383

You might get a faster response from mqtt.org, but.

Is there a specific error that happens when you publish? Presumably you don't see any messages actually published. Do any established subscribers receive any errors?
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Cogito-Ergo-Sum
PostPosted: Mon Aug 27, 2012 11:02 am Post subject: Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

Quote:
You might get a faster response from mqtt.org
I thought, I would ask there; but, I am noticing this in WMQ 7.5 and so ...

Quote:
Is there a specific error that happens when you publish?

When I use the MQTT Client Utility in the MQExplorer, I see Java stack trace beginning as shown below.
Code:
Connection lost (32109)-java.io.EOFException


Quote:
Do any established subscribers receive any errors?

That is even more peculiar ! As soon as I click on Subscribe, I get the same connection lost message (even the 32109) too.

A quick Google showed me this where there is an issue with an existing client ID. This is not applicable in my case as it is WMQ installed on my laptop and I have not connected any client before to this queue manager instance.
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Debugging tip:When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
---Sherlock Holmes
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mqjeff
PostPosted: Mon Aug 27, 2012 11:28 am Post subject: Reply with quote

Grand Master

Joined: 25 Jun 2008
Posts: 17383

Try establishing the subscriber connection before you establish the publisher connection.

Please note that I'm just making guesses here - I've not done anything with this myself.
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Cogito-Ergo-Sum
PostPosted: Mon Aug 27, 2012 8:20 pm Post subject: Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

Quote:
Try establishing the subscriber connection before you establish the publisher connection.

As I mentioned earlier, the subscription also fails with the same reason.

Quote:
Please note that I'm just making guesses here - I've not done anything with this myself.

Anything I could do to help reduce your guesswork ?

I am going to have a look at the security parameters even though, I doubt, if this could cause a failure of client publication. At least the MQTT spec does not mention closure of connection if/when authorization errors happen.
_________________
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-----------------------------
Debugging tip:When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
---Sherlock Holmes
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Cogito-Ergo-Sum
PostPosted: Tue Aug 28, 2012 4:25 am Post subject: Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

With the client ID set to CLIENT01 in the MQTT Client utility I was publishing to MQTT channel. This channel has USECLTID(YES) and MCAUSER wasn't set. I did this on purpose. When I published to a testTopic, the publication failed. I explicitly set-up access for CLIENT01 to allow publishing on the base topic SYSTEM.BASE.TOPIC. This worked.

So, I seem to have resolved this issue; but, have other questions.

Therefore, I have the following questions.

    Should the access to publish/subscribe on SYSTEM.BASE.TOPIC be always granted to allow for publication/subscription to any topic string ? Is a combination of topic object and strings required to specifically limit the publication and subscription topic strings (as described here) ? I got the setmqaut command working for specific topic string; but, the publication still failed.


    Why is the connection lost when publish fails due to access violation ? It is true that the MQTT specification does not explicitly mention anything about the action to be taken on access violations. But, certainly, connection should not be lost?

_________________
ALL opinions are welcome.
-----------------------------
Debugging tip:When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
---Sherlock Holmes
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Cogito-Ergo-Sum
PostPosted: Tue Aug 28, 2012 11:19 pm Post subject: Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

I have been able to publish after providing authorities using topic objects. However, now, I am facing problem with subscriptions. Maybe I am missing something from the documentation.

Can you please help me ?

Here are the steps I am following.
1. Run the mosquitto_sub command as :
Code:
mosquitto_sub -p 1885 -t sensor/temperature/# -i CLIENT03

2. The telemetry channel has MCAUSER set to CHLUSR00.

I see the following in the trace file.
Code:

02:41:06.083.0B  0016  @4e7f4e7f  c.i.m.c.c.wmq.log.DefaultLogger                                        ----+--  {  logNLS(Object,String,String,String) [c.i.mq.MQXRService.MQTTServerSessionV3@76797679,clientidentifier=CLIENT03,conname=/127.0.0.1] <null> [reportSubscribeFailure] [AMQXR0012E: An error occurred whilst subscribing on topic(s) ''sensor/temperature/#'' for ClientIdentifier ''CLIENT03'' userNamer ''CHLUSR00''on channel ''TEST.MQTTCHNL.C''. A reason code of ''2035'' ''MQRC_NOT_AUTHORIZED'' was received during an ''MQOPEN'' operation.]


However, I have set the access to subscribe to the relevant topic object.

Code:
mqm@host:~$ dspmqaut -m QMGR75 -n SENSOR.TEMP -t topic -p CHLUSR00
Entity CHLUSR00 has the following authorizations for object SENSOR.TEMP:
        sub

The topic object is itself shown here:

Code:
DIS TOPIC(SENSOR.TEMP) ALL
     2 : DIS TOPIC(SENSOR.TEMP) ALL
AMQ8633: Display topic details.
   TOPIC(SENSOR.TEMP)                      TYPE(LOCAL)
   TOPICSTR(sensor/temperature)            DESCR( )
   CLUSTER( )                              DURSUB(ASPARENT)
   PUB(ASPARENT)                           SUB(ASPARENT)
   DEFPSIST(ASPARENT)                      DEFPRTY(ASPARENT)
   DEFPRESP(ASPARENT)                      ALTDATE(2012-08-29)
   ALTTIME(00.34.18)                       PMSGDLV(ASPARENT)
   NPMSGDLV(ASPARENT)                      PUBSCOPE(ASPARENT)
   SUBSCOPE(ASPARENT)                      PROXYSUB(FIRSTUSE)
   WILDCARD(PASSTHRU)                      MDURMDL( )
   MNDURMDL( )                             MCAST(ASPARENT)
   COMMINFO( )                             USEDLQ(ASPARENT)
   CUSTOM( )                           

_________________
ALL opinions are welcome.
-----------------------------
Debugging tip:When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
---Sherlock Holmes
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Cogito-Ergo-Sum
PostPosted: Wed Aug 29, 2012 10:38 am Post subject: Reply with quote

Master

Joined: 07 Feb 2006
Posts: 293
Location: Bengaluru, India

The problem exists even when subscribing to fully qualified topic strings.
_________________
ALL opinions are welcome.
-----------------------------
Debugging tip:When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
---Sherlock Holmes
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