Set up and troubleshoot AWS IoT Greengrass with client devices

Set up AWS IoT Greengrass on your core device.

Install the AWS IoT Greengrass Core software by following the instructions in the developer guide.

Check the status of your installation.

Use the following command to check the status of the AWS IoT Greengrass service on your core device:

sudo systemctl status greengrass.service

The expected output of the command is:

Launched Nucleus successfully

Set up an IAM policy and attach it to the Greengrass service role.

Configure and deploy required components in the AWS IoT Greengrass core device.

Configure and deploy the following components:

Confirm that the MQTT bridge allows bidirectional communication.

To relay MQTT messages between client devices and AWS IoT Core, configure and deploy the MQTT bridge component and specify the topics to relay. Here’s an example:

{
  "mqttTopicMapping": {
    "ClientDevicesToCloud": {
      "topic": "dt/#",
      "source": "LocalMqtt",
      "target": "IotCore"
    },
    "CloudToClientDevices": {
      "topic": "cmd/#",
      "source": "IotCore",
      "target": "LocalMqtt"
    }
  }
}

Confirm that the auth component allows client devices to connect and publish or subscribe to topics.

The following aws.greengrass.clientdevices.Auth configuration allows all client devices to connect, publish messages, and subscribe to all topics.

{
  "deviceGroups": {
    "formatVersion": "2021-03-05",
    "definitions": {
      "MyPermissiveDeviceGroup": {
        "selectionRule": "thingName: *",
        "policyName": "MyPermissivePolicy"
      }
    },
    "policies": {
      "MyPermissivePolicy": {
        "AllowAll": {
          "statementDescription": "Allow client devices to perform all actions.",
          "operations": [
            "*"
          ],
          "resources": [
            "*"
          ]
        }
      }
    }
  }
}

Install the AWS IoT Device SDK.

Install the AWS IoT Device SDK on client devices. For a full list of supported languages and the associated SDKs, see the AWS IoT Core documentation.

For example, the AWS IoT Device SDK for Python SDK is located on GitHub. To install this SDK:

Alternatively, you can install the SDK from the source repository:

# Create a workspace directory to hold all the SDK files
mkdir sdk-workspace
cd sdk-workspace
# Clone the repository
git clone https://github.com/aws/aws-iot-device-sdk-python-v2.git
# Install using Pip (use 'python' instead of 'python3' on Windows)
python3 -m pip install ./aws-iot-device-sdk-python-v2

Create a thing.

Download the CA certificate from the Greengrass core device.

If you expect the Greengrass core device to work in offline environments, you have to make the Greengrass core CA certificate available to the client device so it can verify the MQTT broker’s certificate (which is issued by the Greengrass core CA). Therefore, it is important to obtain a copy of this certificate. Use one of the following approaches to download the CA certificate:

Copy credentials in the client devices.

Copy the Greengrass core CA certificate, the device certificate, and the private key in the client devices.

Associate client devices with the core device.

Associate client devices with a core device so that they can discover the core device. The client devices can then use the Greengrass discovery API to retrieve connectivity information and certificates for their associated core devices. For more information, see Associate client devices in the AWS IoT Greengrass documentation.

The client devices that you associated can now use the Greengrass discovery API to discover this core device.

Send data from one client device to another client device.

Use the MQTT client in your device to publish a message on the dt/client1/sensor topic.

Send data from the client device to AWS IoT Core.

Use the MQTT client in your device to publish a message on the dt/client1/sensor topic.

In the MQTT test client, subscribe to the topic that the device is sending messages on, or subscribe to # for all topics (see details).

Send messages from AWS IoT Core to client devices.

On the MQTT test client page, in the Publish to a topic tab, in the Topic name field, enter the topic name of your message. In this example, use cmd/client1 for the topic.