MQTT and SensorThings API MQTT Extension

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Dr. Steve Liang, Ph.D., P.Eng. Associate Professor, University of Calgary Founder and CEO, SensorUp Inc.

About Dr. Steve Liang๏Associate Professor, Geomatics Engineering, Uni. Calgary

๏AITF-Microsoft Industry Research Chair on Open Sensor Web (2011~2014)

๏Chair OGC SensorThings API Standard Working Group

๏Rapporteur, ITU-T SG12/11 on Internet of Things Test Specifications

๏ Founder and CEO, SensorUp Inc

๏Calgary’s Top 40 Under 40

About SensorUp๏We are a leader in Sensor Web and

IoT Platforms

๏We are leading several international IoT standard development efforts (OGC and ITU-T)

๏We are proud member of Eclipse and Open Geospatial Consortium

News - Whiskers๏Whiskers, a new Eclipse

open source project proposal for OGC SensorThings API

๏will includes MQTT support

News - Whiskers๏Whisker is

๏ a Javascript Client Library for SensorThings

๏ a light-weight SensorThings Server for IoT gateways (e.g., Raspberry Pi)

๏ First release - 2016 Q2 or Q3

What will be covered

๏MQTT

๏ SensorThings API MQTT Extension

Why isn’t HTTP enough?

๏HTTP: send a request, receive a response

๏ IoT has fundamentally different challenges

๏ IoT needs a event-oriented paradigm

๏distribute information from 1 to many

๏ get notifications whenever they happen

๏distributing minimal packets of data in huge volumes

๏pushing information over unreliable networks

Why isn’t HTTP enough - 2?

๏ IoT has fundamentally different challenges

๏power consumption is a major concern (battery-powered devices)

๏ responsiveness (near real-time applications)

๏ scalability (50 billion devices!!)

MQTT is…

๏ an ISO standard (ISO/IEC 20922)

๏ an OASIS standard

๏probably the most popular IoT messaging protocol (more in next slide)

๏ efficient and scalable

Messaging Protocols for IoT

1.1%

5.4%

6.8%

8.2%

11.1%

11.5%

18.6%

21.5%

53.0%

63.1%

0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0%

None

DDS

Don’t)know

Proprietary

AMQP

XMPP

In7house

CoAP

MQTT

HTTP

What)general)messaging)protocols)do)you)use)in)your) IoT)solution?

Eclipse IoT Developer Survey 2015

MQTT vs HTTPS (power consumption)

http://stephendnicholas.com/posts/power-profiling-mqtt-vs-https

MQTT vs HTTPS (power consumption)

http://stephendnicholas.com/posts/power-profiling-mqtt-vs-https

What MQTT is not…

๏use MQTT doesn’t mean IoT interoperability

๏ It’s part of the interoperability solution

๏ It still needs a data model standard, such as SensorThings API to enable data interoperability

MQTT Topics

๏ the central concept in MQTT to dispatch messages are topics

๏ a topic is a simple string that can have more hierarchy levels, which are separated by a slash (/),

๏ e.g., house/living-room/temperature

๏ topics are the routing information for the MQTT broker

MQTT in a nutshell

MQTT BrokerPublisher Subscribers

Subscribers

Subscribers

Instead of client/server, MQTT has the roles of publisher/subscriber

subscribe: topic1

subscribe: topic1

subscribe: topic1

MQTT in a nutshell

MQTT BrokerPublisher

Subscribers

Subscribers

Publish to: topic1

body

msg

Instead of client/server, MQTT has the roles of publisher/subscriber

msg

msg

msg

Subscribers

MQTT Methods (verbs)

๏Connect: client request a connection with the MQTT broker

๏Disconnect: disconnect notification

๏ Subscribe: subscribe to topics

๏UnSubscribe: unsubscribe from topics

๏Publish: Publish message

Let’s try

๏HiveMQ provides a nice web socket-based client

๏http://www.hivemq.com/demos/websocket-client/

๏ Today I’m gonna use an Eclipse open source tool called mosquitto

๏GIST here: http://gist.github.com/liangsteve/bb7468fb9e97060f4676d3e544c11a77

MQTT Topics cont.๏plus sign (+) is the single level wild card

๏ e.g., a subscription of house/+/temperature will receive messages published to both house/living-room/temperature and house/bed-room/temperature

๏# is multi-level wildcard

๏ e.g., house/# is subscribing to all topics begins with house

MQTT wildcard

MQTT BrokerPublisher Subscribers

Subscribers

SubscribersInstead of client/server, MQTT has the

roles of publisher/subscriber subscribe to:

h/+/t

subscribe to: house/b/+

subscribe to: h/b/t

MQTT wildcard

MQTT BrokerPublisher Subscribers

Subscribers

SubscribersInstead of client/server, MQTT has the

roles of publisher/subscriber h/+/t

h/b/+

h/b/s

publish to topic: h/b/t

MQTT wildcard

MQTT BrokerPublisher Subscribers

Subscribers

SubscribersInstead of client/server, MQTT has the

roles of publisher/subscriber h/+/t

h/b/+

h/b/s

publish to topic: h/a/t

MQTT QoS๏QoS-0: fire-and-forget

๏QoS-1: deliver at least once

๏ the broker stores messages on disk and retries until clients have acknowledged their delivery. (Possibly with duplicates.)

๏QoS-2: deliver exact once

๏have a second acknowledgement round-trip, to ensure that non-idempotent messages can be delivered exactly once

MQTT Retain Flag

๏ Second, messages have a ‘retain’ flag, indicating that they should be stored for delivery to new subscribers. For topics that are infrequently updated, it’s often useful to give new subscribers the last-known message right away (with an indication that it isn’t fresh). Newer retained messages replace previously ones.

What not included in MQTT?

๏What does the topic mean?

๏ h/p/t ??

๏How to interpret the data pushed to you??

SensorThings API MQTT Extension!!

๏MQTT Subscribe v1.0/Datastreams(id)/Observations

SensorThings MQTT Extension MQTT + OData URL Pattern + O&M

URL path tells you how to find metadata, entity name tells you how to

interpret the data

Receive Observations via MQTT

Get Notified when new a THING was created

Demo - Client received notifications when new THINGS join a SensorThings server

Summary

๏MQTT is very suitable for IoT!!

๏ SensorThings API provides the greatness of both HTTP and MQTT.

๏ SensorThings HTTP REST is suitable for historical data and analytics.

๏ SensorThings MQTT is suitable for real-time applications.

References

๏ Introduction to MQTT

๏ https://www.oasis-open.org/committees/download.php/49205/MQTT-OASIS-Webinar.pdf

๏ Eclipse IoT Survey 2015

๏http://www.slideshare.net/IanSkerrett/iot-developer-survey-2015

See you next week!