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This application demonstrates an iPhone receiving real-time updates from an IoT sensor. The solution is built with AWS AppSync and AWS IoT Core technologies.

Image description


Image description

  1. The sensor component is developed with the AWS IoT Device SDK for Javascript. The sensor is registered as a Thing in IoT Core and publishes a random temperature in a JSON payload to the Cloud every 2 seconds. The Thing Shadow also containes meta-data about then sensor specifying the sensor type as Temperature.
    "value": 84,
    "timestamp": 1570562147790
  1. A rule in IoT Core subscribes to the message topic and forwards the JSON payload to a Lambda function.

  2. The Node js Lambda function executes a GraphQL mutatation in AppSync. The mutation saves the latest value for the sensor in DynamoDB and broadcasts the latest value in real-time to the iOS application. The Lambda function uses an IAM role and policy to obtain permissions to interact with AppSync.

  3. The React Native iOS application subscribes to the AppSync Sensor Update subscription. When new temperature values are received, the gauge component on the screen is updated in real-time to reflect the new sensor value. The iOS application uses Cognito to authenticate users and allow them to perform the AppSync subscription.

Getting Started


  1. A Mac with

    • Xcode (^10.2)
    • Xcode iPhone Simulator enabled. (Simulators can be installed from the "Components" tab in Xcode Preferences)
    • Xcode Command-line Tools
    • CocoaPods
  2. An AWS account in which you have Administrator access.

  3. Node.js (^10.0) with NPM (^6.14)

  4. Amplify CLI (^4.21.0).

After you have installed and configured Amplify, take note of the AWS profile you selected during the configuration. If you created a profile other than default, you will need the profile name for later steps in the deployment.


If you run into issues installing or configuring anything in this project please checkout the Troubleshooting section below.

Clone this code repository

$ git clone

Switch to the mobile folder

$ cd aws-appsync-iot-core-realtime-example/mobile

Install the iOS app's Node.js and CocoaPod packages

$ npm install
$ cd ios
$ pod install
$ cd ..

Initialize your Amplify environment

$ cd aws-appsync-iot-core-realtime-example/mobile
$ amplify init

? Enter a name for the environment: mysandbox
? Choose your default editor: [select your favorite IDE]
? Do you want to use an AWS profile? Yes
? Please choose the profile you want to use: default

When you select your profile, make sure to select the same profile you used when configuring Amplify.

Amplify will then begin to provision your account for the project deployment.

? Do you want to configure Lambda Triggers for Cognito? (Y/n) n

Once your account has been provisioned, entering the 'amplify status' command will show you the resources Amplify will create in your account:

$ amplify status

Current Environment: mysandbox

| Category | Resource name      | Operation | Provider plugin   |
| -------- | ------------------ | --------- | ----------------- |
| Auth     | sensorview74d21f87 | Create    | awscloudformation |
| Api      | sensorview         | Create    | awscloudformation |
| Function | getsensor          | Create    | awscloudformation |
| Function | createsensorvalue  | Create    | awscloudformation |
| Iotrule  | createsensorvalue  | Create    | awscloudformation |

Deploy the app infrastructure to your AWS account

$ amplify push

? Do you want to update code for your updated GraphQL API (Y/n) Y

? Do you want to generate GraphQL statements (queries, mutations and subscription) based on your schema types? This will overwrite your current graphql queries, mutations and subscriptions (Y/n) Y

You will then see a series of output as Amplify builds and deploys the app's CloudFormation Templates, creating the app infrastucture in your AWS account.

Resources being created in your account include:

  • AppSync GraphQL API
  • DynamoDB table
  • Cognito user pool
  • Lambda functions (2)
  • IoT Rule

Install the IoT Sensor

Open a new terminal window then switch to the app's sensor folder (aws-appsync-iot-core-realtime-example/sensor).

Install the Node.js packages, and run the Node.js app to create your sensor as a Thing in AWS IoT Core. It will also create and install the certificates your sensor needs to authenticate to IoT Core.

From the sensor folder:

$ npm install
$ node create-sensor.js

*Note - this will create the sensor using your default AWS profile account and region. If you have not specified a default region in your local AWS configuration, it will default to us-east-1.

If you do not have a default profile or you are using a profile other than default, run the app with an AWS_PROFILE environment variable specifiying the profile name you would like to use.

Replace [my-aws-profile] with the name of your profile:

$ AWS_PROFILE=[my-aws-profile] node create-sensor.js

Run the App

Start the IoT Sensor

From the sensor terminal window:

$ node index.js

You will see output from the app as it connects to IoT Core, transmits its shadow document, and publishes new temperature messages every 2 seconds.

connected to IoT Hub

published to shadow topic $aws/things/sensor-1592073852935/shadow/update {"state":{"reported":{"sensorType":"Temperature"}}}

published to topic dt/sensor-view/sensor-1592073852935/sensor-value {"value":77,"timestamp":1592073890804}

published to topic dt/sensor-view/sensor-1592073852935/sensor-value {"value":76,"timestamp":1592073892807}

published to topic dt/sensor-view/sensor-1592073852935/sensor-value {"value":77,"timestamp":1592073894810}

Keep this app running and switch to your mobile terminal window.

Start the iPhone app

Switch back to the terminal window pointing to the mobile folder and run:

$ npx react-native run-ios

This will launch Xcode's iPhone simulator and a new terminal window that serves up the app.

The default simulator is "iPhone X". If you wish to run your app on another iPhone version, for example an iPhone 11 Pro Max, run:

$ npx react-native run-ios --simulator="iPhone 11 Pro Max"

The simulator name must correspond to a device available in Xcode. You can check your available devices by running the following command from the console.

$ xcrun simctl list devices 

Sign-up and Sign-in

The iOS app requires users to authenticate via Cognito. The first screen you will see is a logon screen. Tap the Sign Up link and then tap the link to Create account and create a new account using your email address.

Cognito will then email you a confirmation code. Enter this code into the subsequent confirmation screen and logon to the app with your credentials.

Use the App!

You should now see a screen similar to the one at the top of this guide. If you look at the terminal window running the sensor app, you shoud see the values being published to the Cloud reflected in the iPhone app's sensor gauge in real-time.


Once you are finished working with this project, you may want to delete the resources it created in your AWS account.

From the mobile folder:

$ amplify delete
? Are you sure you want to continue? (This would delete all the environments of the project from the cloud and wipe out all the local amplify resource files) (Y/n)  Y

From the sensor folder:

$ node delete-sensor.js


Installing Amplify

$ npm install -g @aws-amplify/cli

If you receive EACCES permisisons errors, make sure your system is setup properly to install global packages. See this Guide for options.

Starting the iPhone App in the Simulator

$ npx react-native run-ios

When the iPhone simulator first starts you may see a red error screen related to the URL. This can occur if the simulator starts before the app in the terminal window finishes loading. If you see this:

  1. wait a few seconds
  2. click on the simulator
  3. hit the cmd-R key combination

This will cause the simulator to reload the app.

Installing Pods or the Xcode Build

If pod install or npx react-native run-ios give you errors outside of the simulator try ensuring Xcode Developer tools are installed via

$ xcode-select --install

Make sure CocoaPods are installed

$ sudo gem install cocoapods

If you get an error like "xcrun: error: unable to find utility “simctl”, not a developer tool or in PATH", ensure Xcode tools are pointing to your Xcode Application via

$ sudo xcode-select -s /Applications/ 


This sample code is made available under a modified MIT-0 license. See the LICENSE file.

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