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| Re: [mosquitto-dev] keep-alive in Mosquitto and in MQTT v5/v3.1.1 | 
  
  
    Keep in mind that the value of zero for Keep Alive is a special
    indicator to turn it off (i.e. don't use Keep Alive). 
    
    So don't think of the specs as saying you can "go down to zero".
    Technically, I guess, a 1-sec Keep Alive should be supported, but
    practically, this would induce a huge overhead on the broker. If you
    had ten thousand clients pinging at that rate, it would be hitting
    the broker with 10k msgs/sec just to maintain otherwise quiet
    connections.
    
    So you will find that many clients won't let you set a Keep Alive of
    less than 5 or 10, and default to something like 30, 45, or 60.
    
    Whether a _client_ is required to support all values 1-65535 is
    debatable. Technically, a _broker_ probably should, to be 100%
    compliant, but allowing really low values would let some clients put
    a large burden on the broker.
    
    Frank
    
    
On 9/25/23 09:06, Lemburg, Martin via
      mosquitto-dev wrote:
    
    
      
      
      
      
        Hello,
         
        May be a naive question, but why I can only
            connect with Mosquitto to a broker with a keep-alive greater
            or equal to 5, while the protocols allow a zero keep-alive?
         
        That’s all for the beginning.
         
        Best regards
        Martin
       
      
      
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