Configure an MQTT group connection

Add a group connection to your MQTT Broker data source hierarchy

1. Select the MQTT Broker connection, right-click it, and then select Add MQTTGroup Connection on the shortcut menu.

   A new MQTT group connection is created in the hierarchy tree and is named New_MQTTGroup_000 by default. Rename it, if desired.

   The New_MQTTGroup_000 Parameters configuration view (right pane) is displayed.

   

2. The Device Group Name field is automatically filled in and cannot be edited. The Device Group Name is used for accessing MQTT data from a DDE/SuiteLink client.

3. Select a level of Quality of Service (QoS) from the drop down list. The QoS level determines message delivery parameters, with 0 as the lowest level of service, and 2 as the highest level.

   • 0 - At Most Once: The message will be delivered no more than one time, meaning that it may not be delivered. There is no backup of the message, and if the connection to the client is lost, the message will not be delivered. No delivery acknowledgement is provided.

   • 1 - At Least Once: The message will delivered at least one time, but it may be delivered more than once if the sender does not receive an acknowledgement of a successful transmission. The sender stores the message until a receipt acknowledgement is received.

   • 2 - Exactly Once: The message is delivered one time only. The sender stores the message until it receives confirmation of receipt. This is the safest, and slowest, message transfer mode.

     Note: If the MQTT publisher has a different QoS than the configured QoS, the configured QoS is used.

4. Select the Retain checkbox to retain the latest message and store it in the MQTT broker. By default, this checkbox is not selected.

Enter user credentials for the group connection (optional)

5. In the Identity section, select the Enable checkbox to turn on authentication for subscribing to MQTT messages.

   Note: If you enable this option, it is highly recommended that you enable MQTT Connection Security to protect the username and password.

   The Gateway Communication Driver uses the user name and password settings that you enter here to connect to the configured MQTT broker. If the MQTT sources encrypt the payloads with different user names and passwords, you must create additional groups to support them.

6. Enter the user credentials (user name and password) to be used for subscribing to MQTT messages. This must match a valid MQTT user name at run time. However, the user name is not validated during configuration. The password would be used by MQTT publisher to validate the subscriber. Prior to saving user credentials, you can select Show Password to briefly display the password in clear text for verification.

7. Select Validate Identity, to verify that the MQTT Broker can be accessed on the configured MQTT channel.

Enable Store and Forward for the group connection (optional)

The Store and Forward feature allows you to store published data items if you are disconnected from the MQTT broker. Once the connectivity is restored, the data is forwarded to the MQTT broker. To enable this feature, select the Enable Store and Forward for this Group checkbox.

Each MQTT group has a maximum cache file size of 4 GB. If this limit is exceeded, you must select one of the following options in the Storage Limit Options section:

• Wrap-Around Data: The oldest data stored in the cache is discarded to allow storage space for new data.

• Stop Collecting: The system ceases to collect and store any new data. Once the connection is established again, the stored files are forwarded, which reduces the cache size, allowing storage space for new data.