Message Limitation

The maximum length of a publish message on an MQTT topic depends on the MQTT broker implementation and any specific limitations imposed by the broker or the MQTT protocol version being used.

The MQTT specification itself does not define a fixed maximum length for the payload of a publish message. However, most MQTT brokers have their own limitations and constraints.

In general, MQTT brokers may impose restrictions on the maximum size of a publish message to ensure efficient network usage and prevent abuse or denial-of-service attacks. The maximum length can vary depending on factors such as the available memory on the broker, network limitations, or configuration settings.

It is recommended to consult the documentation or specifications of the specific MQTT broker you are using to determine the maximum allowed length for publish messages on topics. The broker's documentation should provide details on any limitations or guidelines regarding the maximum payload size for publish messages.

Additionally, it's good practice to consider the network conditions and potential limitations of the MQTT clients that will be receiving the published messages. It's possible that the clients may have their own constraints on the maximum payload size they can handle. 

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