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Send telemetry to Azure IoT Hub quickstart (Java) | Microsoft Docs
In this quickstart, you run two sample Java applications to send simulated telemetry to an IoT hub and to read telemetry from the IoT hub for processing in the cloud.
dominicbetts
timlt
iot-hub
iot-hub
java
quickstart
mvc
06/22/2018
dobett

Quickstart: Send telemetry from a device to an IoT hub and read the telemetry from the hub with a back-end application (Java)

[!INCLUDE iot-hub-quickstarts-1-selector]

IoT Hub is an Azure service that enables you to ingest high volumes of telemetry from your IoT devices into the cloud for storage or processing. In this quickstart, you send telemetry from a simulated device application, through IoT Hub, to a back-end application for processing.

The quickstart uses two pre-written Java applications, one to send the telemetry and one to read the telemetry from the hub. Before you run these two applications, you create an IoT hub and register a device with the hub.

[!INCLUDE cloud-shell-try-it.md]

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

Prerequisites

The two sample applications you run in this quickstart are written using Java. You need Java SE 8 or later on your development machine.

You can download Java for multiple platforms from Oracle.

You can verify the current version of Java on your development machine using the following command:

java --version

To build the samples, you need to install Maven 3. You can download Maven for multiple platforms from Apache Maven.

You can verify the current version of Maven on your development machine using the following command:

mvn --version

Download the sample Java project from https://github.com/Azure-Samples/azure-iot-samples-java/archive/master.zip and extract the ZIP archive.

Create an IoT hub

[!INCLUDE iot-hub-quickstarts-create-hub]

Register a device

A device must be registered with your IoT hub before it can connect. In this quickstart, you use the Azure CLI to register a simulated device.

  1. Add the IoT Hub CLI extension and create the device identity. Replace {YourIoTHubName} with the name you chose for your IoT hub:

    az extension add --name azure-cli-iot-ext
az iot hub device-identity create --hub-name {YourIoTHubName} --device-id MyJavaDevice

    If you choose a different name for your device, update the device name in the sample applications before you run them.

  2. Run the following command to get the device connection string for the device you just registered:

    az iot hub device-identity show-connection-string --hub-name {YourIoTHubName} --device-id MyJavaDevice --output table

    Make a note of the device connection string, which looks like Hostname=...=. You use this value later in the quickstart.

  3. You also need the Event Hubs-compatible endpoint, Event Hubs-compatible path, and iothubowner primary key from your IoT hub to enable the back-end application to connect to your IoT hub and retrieve the messages. The following commands retrieve these values for your IoT hub:

    az iot hub show --query properties.eventHubEndpoints.events.endpoint --name {YourIoTHubName}

az iot hub show --query properties.eventHubEndpoints.events.path --name {YourIoTHubName}

az iot hub policy show --name iothubowner --query primaryKey --hub-name {your IoT Hub name}

    Make a note of these three values, which you use later in the quickstart.

Send simulated telemetry

The simulated device application connects to a device-specific endpoint on your IoT hub and sends simulated temperature and humidity telemetry.

  1. In a terminal window, navigate to the root folder of the sample Java project. Then navigate to the iot-hub\Quickstarts\simulated-device folder.

  2. Open the src/main/java/com/microsoft/docs/iothub/samples/SimulatedDevice.java file in a text editor of your choice.

    Replace the value of the connString variable with the device connection string you made a note of previously. Then save your changes to SimulatedDevice.java file.

  3. In the terminal window, run the following commands to install the required libraries and build the simulated device application:

    mvn clean package

  4. In the terminal window, run the following commands to run the simulated device application:

    java -jar target/simulated-device-1.0.0-with-deps.jar

    The following screenshot shows the output as the simulated device application sends telemetry to your IoT hub:

    Run the simulated device

Read the telemetry from your hub

The back-end application connects to the service-side Events endpoint on your IoT Hub. The application receives the device-to-cloud messages sent from your simulated device. An IoT Hub back-end application typically runs in the cloud to receive and process device-to-cloud messages.

  1. In another terminal window, navigate to the root folder of the sample Java project. Then navigate to the iot-hub\Quickstarts\read-d2c-messages folder.

  2. Open the src/main/java/com/microsoft/docs/iothub/samples/ReadDeviceToCloudMessages.java file in a text editor of your choice. Update the following variables and save your changes to the file.

    Variable Value
    eventHubsCompatibleEndpoint Replace the value of the variable with the Event Hubs-compatible endpoint you made a note of previously.
    eventHubsCompatiblePath Replace the value of the variable with the Event Hubs-compatible path you made a note of previously.
    iotHubSasKey Replace the value of the variable with the iothubowner primary key you made a note of previously.

  3. In the terminal window, run the following commands to install the required libraries and build the back-end application:

    mvn clean package

  4. In the terminal window, run the following commands to run the back-end application:

    java -jar target/read-d2c-messages-1.0.0-with-deps.jar

    The following screenshot shows the output as the back-end application receives telemetry sent by the simulated device to the hub:

    Run the back-end application

Clean up resources

[!INCLUDE iot-hub-quickstarts-clean-up-resources]

Next steps

In this quickstart, you've setup an IoT hub, registered a device, sent simulated telemetry to the hub using a Java application, and read the telemetry from the hub using a simple back-end application.

To learn how to control your simulated device from a back-end application, continue to the next quickstart.

[!div class="nextstepaction"] Quickstart: Control a device connected to an IoT hub