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CSE 122 / 222C ; WES 269�MQTT

Pat Pannuto, UC San Diego

ppannuto@ucsd.edu

CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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MQTT Goals

  • Quick primer on a very commonly used, lightweight protocol for data

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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Outline

  • MQTT Primer

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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MQTT Origins & Design Goals

  • First use: Monitoring for ”highly remote” oil pipelines
    • Very limited (and costly) communications infrastructure 🡪 minimal protocol

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  • MQTT doesn’t stand for anything
    • It is not a “Message Queue”

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  • Base case is still very simple/minimal, but there are lots of expansions now
    • Security enhancements as well as MQTT-SN most relevant to you
    • https://mqtt.org/mqtt-specification/

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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MQTT is a “pub/sub” protocol�An answer to the “where do you send data” question

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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MQTT Roles

  • Broker
    • Server that distributes information

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  • Client
    • Any device connected to the Broker

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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Pub/Sub Architecture

  • Topic
    • String that names the data being sent

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  • Publish
    • Sends data with an associated Topic to Broker

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  • Subscribe
    • Inform Broker of which Topics you want data from
    • ALL subscribed Clients get copies of the data

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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MQTT Access Control

  • Nothing is required by default
    • Which is its own concern

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  • Can require a password to communicate with Broker
    • Which by default is sent in the clear, over the Internet [use MQTTS instead]

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  • Can make access control lists on a per-topic basis
    • Each user with a given password can only access certain topics

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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Value of MQTT

  • And that’s pretty much everything there is to MQTT
    • MQTT is very simple, and that’s a benefit
    • Packets are sent over TCP, so the reliability is already handled sufficiently
      • Variants can function over UDP instead

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  • How is data formatted?
    • However you want. It’s just bytes attached to a Topic string
    • Could be an array of data bytes, JSON blob, image data, whatever
      • Up to MB of data in a single payload

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    • Application-level probably knows how to decode

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell

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Next Up: Longer-Range Technologies

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CSE 122/222C ; WES 269 [WI25]

CC BY-NC-ND Pat Pannuto – Content developed in coordination with Branden Ghena and Brad Campbell