Powering your next IoT application with MQTT - JavaOne 2014 tutorial

transcript

Powering your next IoT application with

Julien VermillardBenjamin Cabé

Your devoted presenters :-)

Julien Vermillard / @vrmvrm

● Software Engineer at Sierra Wireless● Implementing various protocols for our cloud

service (AirVantage)● Apache Software Foundation member● Eclipse committer on Californium, Wakaama and Leshan

Your devoted presenters :-)

Benjamin Cabé / @kartben

● IoT Evangelist at the Eclipse Foundation● Hack things – Arduino, Raspberry Pi, Glass, …● Traveler and photographer

Agenda

Internet of Things 101What protocol should I use?MQTT

What is MQTT?Features overviewMQTT at Eclipse

HANDS-ON!More MQTT cool stuff

Tutorial goal

Go from our first dead simple MQTT client app to a complete end-to-end solution for …

reporting,consolidating and charting sensor data

… coming from a connected greenhouse

Tutorial steps

Step 0The greenhouse setup

Step 1Write your first MQTT client

Step 2Create an MQTT bot to consolidate live data

Step 3Live JavaFX dashboard

Photo by Clover_1

What you will need

Eclipse IDEBasic Java knowledgeYour brainzzz

Machine-to-Machine?

Machine-to-Machine?Internet of Things?

Technology that supports

wired or wireless

communication

between devices

IoT protocols

… devices are constrained… network is constrained

… applications are heterogeneous

Different needs

Device ManagementRadio statististics, device configuration, …OMA-DM, TR-069, Lightweight M2M…

Local sensor networksTransmit sensor data, usually over RF or PLCZigbee, X10, Bluetooth Smart, …

End-user applicationsDisplay sensor data on mobile app, dashboards, …HTTP, Websockets, ...

Find your way through the IoT protocols jungle

Continental 1/2/3, Thursday @11.00am

M is for Messaging… (mmmmaybe!) Q is not for Queue

Publish/Subscribe protocolLightweight (bandwidth, battery, …)

ee232/emp SUB

ee232/

MQTT history

… it’s not new!

Invented in 1999 (Andy Stanford-Clark, Arlen Nipper)

Royalty-free since 2010

Being standardized at OASIS - final spec to be released soon

Neat MQTT features

WildcardsQuality of ServiceLast Will & TestamentRetained Messages

MQTT Features | Wildcards

● The number sign (#) is a wildcard character that matches any number of levels within a topic.

● The plus sign (+) is a wildcard character that matches only one topic level

Examplesmygreenhouse/sensors/#+/sensors/temperature

MQTT Features | QoS

QoS flag allows to control the level of assurance for delivery you want when publishing a message to the broker

MQTT Features | QoS 0

A message published with QoS=0 will be received at most once (“fire & forget”) by subscribed clients

A message published with QoS=1 will be received at least once (acknowledged delivery) by subscribed clients

A message published with QoS=2 will be received exactly once (assured delivery) by subscribed clients

MQTT Features | Last Will & Testament

IoT devices can come & go on the network quite often and in a very unpredictable way

Last Will & Testament allows to notify interested parties to an abnormal disconnection of a client

The Last Will & Testament (if any) is part of the initial connection message

MQTT Features | Retained messages

The Retained flag allows a published message to be stored on the broker, so as possible receivers can subscribe later and still receive the message

MQTT at Eclipse

Moquette

Eclipse Paho

Open-source implementations of MQTT clientsPick your language!

Java, JavaScript, C/C++, Go, Obj C, Lua, Python …

http://eclipse.org/pahohttps://dev.eclipse.org/mailman/listinfo/paho-dev

Eclipse Mosquitto

Lightweight server implementation of MQTT (MQTT-SN to come), written in CLightweight?

Executable is ~120kB~3MB RAM with 1000 clients connected

http://eclipse.org/mosquittohttps://dev.eclipse.org/mailman/listinfo/mosquitto-dev

Eclipse Moquette

A pure Java broker

Supports QoS 0, 1, 2

Websockets

Event-driven: based on Netty and LMAX disruptor

Hands-on!

Step #0iot.eclipse.orgMQTT broker

YOU :-)

Step #0

The Kura application can be seen as an MQTT client that:

● publishes sensor data to topics● is subscribed to commands

Root topic:javaonedemo/eclipse-greenhouse/

Sensor data on sensors/... subtopic, Actuators on actuators/... subtopic

Creating a Java Internet of Things Gateway

Continental 1/2/3, Tuesday @2.30pm

End-to-End IoT Solutions with Java and Eclipse IoT

Continental 1/2/3, Today @11.00pm

Contents of the USB stick

● Eclipse IDE for Windows, Linux and OS X● Sample projects to be imported in your workspace

+ Paho java client JAR file● Completed projects

Tutorial source code

Check out:https://github.com/kartben/mqtt-tutorial-javaone2014

Getting started

● Launch Eclipse● Import projects contained on the USB stick

○ File > Import… > Existing projects into workspace

Step #1

Use the Java MQTT client from Paho to exchange our first messages with a broker

Key concepts:● Connect/disconnect to a broker● Topic structuring best practices● Publish/subscribe messages● QoS

Photo Credit:oskay

MQTT Topics best practices

Photo Credit:oskay

That’s a tough question… are there best practices as to how to organize your local filesystem…?

Photo Credit:oskay

● Topic hierarchy is what will allow you to do smart wildcard matching○ objectID/temp is better than temp/objectID

● No need to start with a ‘/’● Persist your topics if you can afford it

Interesting thoughts in this session from IoT Day Grenoble https://www.youtube.com/watch?v=yQAsjGFewk8

MQTT for Java API

MqttClient● Main class allowing to connect to a broker

MqttMessage● What you send to or receive from a broker● Arbitrary binary payload (ie byte array)

MqttCallback● For a given MqttClient, the MqttCallback is

where you handle received messages, delivery ACK, and loss of connection

Connecting to a broker

MqttClient#connect(serverURI, clientId)

URI can be something like:● tcp://iot.eclipse.org:1883● ssl://my.secured.broker:8883

The client ID must be unique on a given brokerIts main use is keeping subscriptions intact for unreliable endpoints (see the Clean session flag)

Retrieving data

Complete step1 project:

1. Connect to iot.eclipse.org2. Subscribe to:

javaonedemo/eclipse-greenhouse/sensors/#

3. Observe the data coming in4. (optional) Publish a message (‘on’ or ‘o ’) to:

javaonedemo/eclipse-greenhouse/actuators/light

- Think about what QoS is best suited for controlling the LED- To persist or not to persist?

Questions?

Step #2

Leverage retained messages to build a bot that consolidates (min, max, avg) sensor data

Key concepts:● Asynchronous client● Retained messages● Data consolidation

Data consolidation workflow

“PUBLISH”javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.2

javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.2javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.1javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.26javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.0javaonedemo/eclipse-greenhouse/sensors/temperaturePayload: 23.9

“PUBLISH”greenhouse/LIVE/benjamin-bbb/data/temperaturePayload: 23.2

Local consolidation

“PUBLISH”greenhouse/LIVE/benjamin-bbb/data/temperaturePayload: 23.2

Local consolidation

“PUBLISH RETAIN”javaonedemo/CONSOLIDATED/…eclipse-greenhouse/sensors/…2014/09/28/09/43Payload: 23.312

MqttAsyncClient

Same as MqttClient but allowing to perform operations asynchronously!● i.e. it will allow us to asynchronously publish a message

from within the messageArrived callback● Methods are not very different from MqttClient except that

they optionally accept an IMQTTActionListenerCallback (called when operation has finished), and return an IMqttToken to be used for tracking the completion of a task

Questions?

Step #3

Use JavaFX Charts to display live sensor data

JavaFX Charts

Questions?

Other cool MQTT uses

MQTT over WebSockets● Build a web UI with no backend● Broker support in Mosquitto,

Moquette, …● Many JS-based time-series

graph engines: D3.js, Rickshaw, …

https://www.eclipse.org/paho/clients/js/

MQTT on embedded devices● Arduino, ● mbed, ● etc.

https://www.eclipse.org/paho/clients/c/embeddedMore info on Ian Cragg’s blog.

MQTT on Google Glass● You just need a regular

Java Paho client!● “OK Glass, control the roof!”● You might want to check out the Android

service available in Paho’s Java ‘develop’ branch

Thanks!

More questions? Feel free to contact us!

Benjamin Cabé@kartben

benjamin.cabe@eclipse.org

Julien Vermillard@vrmvrm

jvermillard@sierrawireless.com