Re: [paho-dev] Hi Paho team.

[Dave Locke <locke@xxxxxxxxxx>]

Hi Jianing, 
the use of waitForCompletion() and and
the deliveryComplete() callback are not normally used together:

• waitForCompletion() turns an an asynchronous operation like publish (on the MqttAsyncClient) into a blocking operation.  Once the waitForCompletion() call returns the publish has completed
• deliveryComplete() is used with the asynchronous publish method to notify the app when the delivery of the message is complete.

i,e. they both solve the same problem
but in different ways - one blocks and the other does not. 

Messages can be published in the callbacks
such as the messageArrived() callback but the implementation of the callback
must return promptly and not use a blocking call.  Hence waitForCompletion()
must not be used in the messageArrived() callback.   If the message
is published from the messageArrived() callback  without the use of
waitForCompltion() then the deliveryComplete() method will be notified
when delivery is complete. If this is not the case it is a bug. 

All the best 
Dave Locke

Senior Inventor, Pervasive and Advanced Messaging Technologies

locke@xxxxxxxxxx Dave Locke/UK/IBM@ibmgb 7-246165 (int) +44 1962816165 (ext) 37274133 (mobex) +44 7764132584 (ext)

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From:      
 Jianing Ren <jianingr@xxxxxxxxxxxx>
To:      
 paho-dev@xxxxxxxxxxx
Date:      
 28/11/2013 23:56
Subject:    
   [paho-dev] Hi
Paho team.
Sent by:    
   paho-dev-bounces@xxxxxxxxxxx

---

Hi Paho team,


I am not sure if it counts as a bug in mqtt Java client
implementation that is when I publish the topic and calling waitforcompletion(),
If this topic was published from messageArrived call back method. I will
never get the completeDelivery call back again. And it seems  got
block unless the published message I sent in the messageArrived() call
back was un other thread.


For example:
public void send(Topic topic){
token = topic.publish();
token.waitforcompletion();
}



public void completeDelivery(Token){
printout(token.getmessageID());
}



public void messageArrived(message){
….have received message

..now send back reply.
send("reply"); …This reply message will be
blocked and never call "completeDelivery". 
Thread thread = new thread();

thread.start
{
send("reply"); If reply sending in other thread,
then worked.
}

}


Thanks. 


Regards,
 
Jianing Ren







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