Connect your MQTT Client

In this tutorial we will use the MQTT API to subscribe to changes of asset attributes values and publish data to them from a MQTT Client. The OpenRemote Manager functions as the MQTT Broker. You can use a desktop MQTT client (e.g. MQTT Explorer or MQTT X) for this tutorial, or better yet the device you want to connect.

Create an asset with attributes

We will create a Thing asset, but feel free to use an AssetType that matches your physical device

1. On the assets page, click the + in the asset tree on the left
2. Select the Thing asset type, give it a friendly name and click 'Add'
3. Add two new attributes in the Edit asset mode:
   1. subscribeAttribute
      • type: Custom Attribute
      • name: subscribeAttribute
      • Valuetype: Boolean
   2. writeAttribute
      • type: Custom Attribute
      • name: writeAttribute
      • Valuetype: Number

Create a service user

The service user will give programmatic access to the MQTT client.

1. Go to the users page and create a new service user (second panel on the page)
2. Name the service user mqttuser and give the user the read and write role for the sake of convenience. It is advised to configure a more restricted role for your service users.
3. Click 'Create', a secret will be generated automatically.
4. Open the 'mqttuser' user to see and copy the secret

Establish a connection from client to broker

In your MQTT client set up a new connection:

• host: mqtt://localhost (or URL of your hosted environment e.g. demo.openremote.io)
• Port: 8883 with TLS/SSL enabled; most clients will work with our self generated Let's Encrypt certificates, but if using a self signed certificate or your client isn't able to validate the cert chain then you may need to explicitly load the cert into your client or disable/relax the client's TLS verification settings (refer to your specific client's documentation). It is possible to expose the broker un-encrypted on port 1883 by creating a port mapping for that on the manager service in your Docker Compose file
• password: the secret generated for the MQTT service user (you can find it on the mqttuser users page)
• username: master:mqttuser ({realm}:{user})
• clientID: client123 (this can be anything you like but must be unique - Any existing connection with the same client ID will be replaced. Make sure this clientID remains identical.)

Subscribe to attributes using the MQTT API

In this tutorial we will be looking at specific attributes of a specific asset. There are many more options of subscribing to (all) updates of assets and attributes. The asset attributes that you will be subscribing to can be written by the user, by rules, or can be a live value gathered through an Agent link with another device in the field. You can imagine this boolean value could toggle a function of the device subscribed to the attribute

1. Get the ID of the Thing asset by navigating to its asset page and copying the ID in the URL (e.g. http://localhost:9000/manager/#!assets/false/6xIa9MkpZuR7slaUGB6OTZ => 6xIa9MkpZuR7slaUGB6OTZ)
2. Create a subscription for the subscribeAttribute in your MQTT client with the topic: {realm}/{clientId}/attribute/{attributeName}/{assetId}. So in our case this will be master/client123/attribute/subscribeAttribute/6xIa9MkpZuR7slaUGB6OTZ
3. In the view mode of the Thing asset in the OpenRemote Manager, write a new value to the 'Subscribe attribute' by clicking the checkbox.
4. Verify that you see the value (true/false) coming in on your MQTT client!

Publish attribute values from the MQTT client

You can publish data from your MQTT client (device) to the OpenRemote manager so that you can monitor the device and create rules.

1. Define the correct topic. For directly writing an attribute value: {realm}/{clientID}/writeattributevalue/{attributeName}/{assetID}. So in our case this will be master/client123/writeattributevalue/writeAttribute/6xIa9MkpZuR7slaUGB6OTZ
2. Send the JSON over this topic. For a Number, this is really simple: 23
3. Go to the Manager and check if the value updated!