Unlimited keepalive in MQTT

user_922871 0
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Currently developing something like "smart home" and I have few different devices in my home. All of them connected to OpenHab via MQTT. I'm using Paho MQTT library (Python) for my purposes.

Generally, MQTT has "keepalive" property. This property describes how much time my client will be connected (AFAIK it sends the ping to the server) to MQTT server when there are no updates on the subscribed topic.

But here I have a huge problem. Needed topic could be updated once per hour or even once per few days/months. Let's say that this is indoor alarm. How can I avoid that keepalive timeout or ignore that field? Could it be unlimited?

paho mqtt python
3 Answers

When sending the initial MQTT CONNECT message from a client, you can supply an optional "keep-alive" value. This value is a time interval, measured in seconds, during which the broker expects a client to send a message, such as a PUBLISH message. If no message is sent from the client to the broker during the interval, the broker automatically closes the connection. Note that the keep-alive value you specify is multiplied by 1.5, so setting a 10-minute keep-alive actually results in a 15 minute interval.

user_89150220

Have a look at the Keep Alive section of the MQTT specification:

A Keep Alive value of 0 has the effect of turning off the Keep Alive mechanism. If Keep Alive is 0 the Client is not obliged to send MQTT Control Packets on any particular schedule. v5 spec source

Therefore, set the keep alive to 0, and then the client doesn't have to send a keep alive signal as often. The server should respect that this connection with a client (e.g. from last year) should still be connected, but it won't be guaranteed (The client might be disconnected when the server is shut down).

user_73658660
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