IoTHub data visualization in web application

This repo contains code for a web application, which can read temperature and humidity data from IoT Hub and show the real-time data in a line chart on the web page.

Browser compatiblity

Browser Verified version
Edge 44
Chrome 76
Firefox 69

This tutorial, also published here, shows how to set up a nodejs website to visualize device data streaming to an Azure IoT Hub using the event hub SDK. In this tutorial, you learn how to:

  • Create an Azure IoT Hub
  • Configure your IoT hub with a device, a consumer group, and use that information for connecting a device and a service application
  • On a website, register for device telemetry and broadcast it over a web socket to attached clients
  • In a web page, display device data in a chart

If you don't have an Azure subscription, create a free account before you begin.

You may follow the manual instructions below, or refer to the Azure CLI notes at the bottom to learn how to automate these steps.

Sign in to the Azure portal

Sign in to the Azure portal.

Create and configure your IoT hub

  1. Create, or select an existing, IoT hub.

    • For Size and Scale, you may use "F1: Free tier".
  2. Select the Settings | Shared access policies menu item, open the service policy, and copy a connection string to be used in later steps.

  3. Select Settings | Built-in endpoints | Events, add a new consumer group (e.g. "monitoring"), and then change focus to save it. Note the name to be used in later steps.

  4. Select IoT devices, create a device, and copy device the connection string.

Send device data

Run the visualization website

Clone this repo. For a quick start, it is recommended to run the site locally, but you may also deploy it to Azure. Follow the corresponding option below.

Inspect the code

Server.js is a service-side script that initializes the web socket and event hub wrapper class, and provides a callback to the event hub for incoming messages to broadcast them to the web socket.

Scripts/event-hub-reader.js is a service-side script that connects to the IoT hub's event hub using the specified connection string and consumer group, extracts the DeviceId and EnqueuedTimeUtc from metadata, and then relays message using the provided callback method.

Public/js/chart-device-data.js is a client-side script that listens on the web socket, keeps track of each DeviceId, and stores the the last 50 points of incoming device data. It then binds the selected device data to the chart object.

Public/index.html handles the UI layout for the web page, and references the necessary scripts for client-side logic.

Run locally

  1. To pass parameters to the website, you may use environment variables or parameters.

    • Open a command prompt or PowerShell terminal and set the environment variables IotHubConnectionString and EventHubConsumerGroup.

      Syntax for Windows command prompt is set key=value, PowerShell is $env:key="value", and Linux shell is export key="value".

    • Or, if you are debugging with VS Code, you can edit the launch.json file and add these values in the env property.

      "env": {
          "NODE_ENV": "local",
          "IotHubConnectionString": "<your IoT hub's connection string>",
          "EventHubConsumerGroup": "<your consumer group name>"
  2. In the same directory as package.json, run npm install to download and install referenced packages.

  3. Run the website one of the following ways:

    • From the command-line (with environment variables set), use npm start
    • In VS Code, press F5 to start debugging
  4. Watch for console output from the website.

  5. If you are debugging, you may set breakpoints in any of the server-side scripts and step through the code to watch the code work.

  6. Open a browser to http://localhost:3000.

Use an Azure App Service

The approach here is to create a website in Azure, configure it to deploy using git where it hosts a remote repo, and push your local branch to that repo.

Note: Do not forget to delete these resources after you are done, to avoid unnecessary charges.

  1. Create a Web App.

    • OS: Windows
    • Publish: Code
    • App Service Plan: choose the cheapest plan (e.g. Dev / Test | F1)
  2. Select Settings | Configuration

    1. Select Application settings and add key/value pairs for:
      • Add IotHubConnectionString and the corresponding value.
      • Add EventHubConsumerGroup and the corresponding value.
    2. Select General settings and turn Web socksets to On.
  3. Select Deployment Options, and configure for a Local Git to deploy your web app.

  4. Push the repo's code to the git repo URL in last step with:

    • In the Overview page, find the Git clone URL, using the App Service build service build provider. Then run the following commands:

      git clone
      cd web-apps-node-iot-hub-data-visualization
      git remote add webapp <Git clone URL>
      git push webapp master:master
    • When prompted for credentials, select Deployment Center | Deployment Credentials in the Azure portal and use the auto-generated app credentials, or create your own.

  5. After the push and deploy has finished, you can view the page to see the real-time data chart. Find the URL in Overview in the Essentials section.


If you encounter any issues with this sample, try the following steps. If you still encounter issues, drop us a note in the Issues tab.

Client issues

  • If a device does not appear in the list, or no graph is being drawn, ensure the sample application is running on your device.

  • In the browser, open the developer tools (in many browsers the F12 key will open it), and find the Console. Look for any warnings or errors printed here.

    • Also, you can debug client-side script in /js/chart-device-data.js.

Local website issues

  • Watch the output in the window where node was launched for console output.

  • Debug the server code, namely server.js and /scripts/event-hub-reader.js.

Azure App Service issues

  • Open Monitoring | Diagnostic logs. Turn Application Logging (File System) to on, Level to Error, and then Save. Then open Log stream.

  • Open Development Tools | Console and validate node and npm versions with node -v and npm -v.

  • If you see an error about not finding a package, you may have run the steps out of order. When the site is deployed (with git push) the app service runs npm install which runs based on the current version of node it has configured. If that is changed in configuration later, you'll need to make a meaningless change to the code and push again.

CLI documentation

In order to automate the steps to deploy to Azure, consider reading the following documentation and using the corresponding commands.

# Initialize these variables: $subscriptionId, $resourceGroupName, $location, $iotHubName, $consumerGroupName, $deviceId, $appServicePlanName, $webAppName, $iotHubConnectionString

# Login and set the specified subscription
az login
az account set -s $subscriptionId

# Create the resource group in the specified location
az group create -n $resourceGroupName --location $location

# Create an IoT Hub, create a consumer group, add a device, and get the device connection string
az iot hub create -n $iotHubName -g $resourceGroupName --location $location --sku S1
az iot hub consumer-group create -n $consumerGroupName --hub-name $iotHubName -g $resourceGroupName

az iot hub show-connection-string -n $iotHubName -g $resourceGroupName

az iot hub device-identity create -d $deviceId --hub-name $iotHubName -g $resourceGroupName
az iot hub device-identity show-connection-string  -d $deviceId --hub-name $iotHubName -g $resourceGroupName

# Create an app service plan and website, then configure website
az appservice plan create -g $resourceGroupName -n $appServicePlanName --sku F1 --location $location
az webapp create -n $webAppName -g $resourceGroupName --plan $appServicePlanName --runtime "node|10.6"
az webapp update -n $webAppName -g $resourceGroupName --https-only true
az webapp config set -n $webAppName -g $resourceGroupName --web-sockets-enabled true
az webapp config appsettings set -n $webAppName -g $resourceGroupName --settings IotHubConnectionString=$iotHubConnectionString EventHubConsumerGroup=$consumerGroupName

# Configure website for deployment
az webapp deployment list-publishing-credentials -n $webAppName -g $resourceGroupName
az webapp deployment source config-local-git -n $webAppName -g $resourceGroupName

# Push code to website
# Note: the URL is based on the previous two commands of output in the format of https://<web site user>:<password>@$$webAppName.git
git remote add azure <web app git URL>
git push azure master:master

# Open browser to web site home page
az webapp browse -g $resourceGroupName -n $webAppName


In this tutorial, you learned how to:

  • Create an Azure IoT Hub
  • Configure your IoT hub with a device, a consumer group, and use that information for connecting a device and a service application
  • On a website, register for device telemetry and broadcast it over a web socket to attached clients
  • In a web page, display device data in a chart

Note: remember to delete any Azure resources created during this sample to avoid unnecessary charges.