In general this is not possible from MQTT.  It might be possible
      from a specific broker with its own specific facilities.  But what
      you are asking for is essentially what the broker does anyway.  If
      the size of the message you are sending is small, there would be
      little difference in just sending the message vs inquiring as to
      the existence of any subscribers.
    Ian
    
    On 08/18/2016 06:07 PM, Vignesh Aigal
      wrote:
    
    
      Hi,
        
I am looking at using mosquitto for some project. I wanted
          to understand one thing. Is it possible to subscribe to some
          topic which can give information about the lis of current
          subscriptions in the broker? I am looking at a use case
          wherein I would have a publisher publish a message for a topic
          only if there are subscribers for that topic. I understand
          that the publisher and subscriber should be independent, but
          just wanted to check if this is possible 
        
        
        Thanks,
        Vignesh Aigal
      
      
      
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    -- 
Ian Craggs                          
icraggs@xxxxxxxxxx                 IBM United Kingdom
Paho Project Lead; Committer on Mosquitto