Differences between MQTT and MQTT-SN

The main differences between MQTT-SN and MQTT are as follows:

  • There are three CONNECT messages in MQTT-SN versus one in MQTT. The additional two are used to transport the Will topic and Will message explicitly.  
  • MQTT-SN can run over simplified medium and UDP.
  • Topic names are replaced by short, two-byte long topic ID messages. This is to assist with bandwidth constraints in wireless networks.  
  • Pre-defined topic IDs and short topic names can be used without any registration. To use this feature, both the client and server need to use the same topic ID. Short topic names are short enough to be embedded in the PUBLISH message.
  • A discovery procedure is introduced to assist clients and to allow them to find ...

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