MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol ideal for low-bandwidth networks, commonly used in IIoT. This guide will help you use SIA Connect with MQTT Explorer to test connections via a public MQTT endpoint. You'll learn to set up MQTT Explorer, configure SIA Connect, and monitor data exchange, with clear steps for both PLC and simulator setups.

This article will cover the following steps:

• Video guide
• Connecting SIA Connect to a broker
• Setting the correct parameters in MQTT explorer and connect to that same broker
• Send data from SIA Connect to a broker and monitor the data

Video

Connecting SIA Connect to a broker

Create an instance and fill in the required information, outlined below

Click “Save Instance”

Create a new item with the following parameters

{
    "tag": "%ITEM.NAME%",
    "value":%ITEM.VALUE%,
    "timestamp":"%VALUE.TIME%"
}

Click “save item”

Setting the correct parameters in MQTT Explorer and connect to the same broker

In the left-hand menu, choose the option “test.mosquitto.org”. From there, click “Advanced”

From the “Advanced” menu, input the same topic as the one used in the previous step. Click “Add” and “Back”

Click “Connect”

Now that you are connected to the endpoint using MQTT Explorer, you are ready to monitor data sent from SIA Connect to the endpoint. 

Sending data from SIA Connect to a broker and monitoring the data

If you have a PLC to test with

Set up your PLC Instance and items 

All documentation regarding creating PLC instances can be found on this link

Create a mapping between the PLC and the MQTT Item

When you have your PLC instances and items, you need to create a mapping between a PLC item and the MQTT item, created in a previous step. 

This is done from the inside the instance. From here, click on “New mapping”

From the popup menu, fill out the necessary information

Click “Save mapping”

Make sure data is sending

SIA Connect will only execute a mapping, when the sender item updates - in this case, the sender item is the PLC item. 

If the PLC does not update the value of the item through the program, we can force the update to take place. This is done by modifying the trigger behavior of the item. Changing the trigger behavior to “All” will update the item and trigger any associated mappings, even when the value does not update

If you do not have a PLC to test with

If you do not have a PLC to test with, SIA Connect offers another option - the Simulator Connector. This connector will allow you to create instance, which will generate data as was it a PLC. 

Installing the connector

On the SIA Connect web-interface, navigate to the “Connectors” menu. From here, use the search function 

1. Navigate to the “Connectors” menu
2. Use the search function to search for “Simulator”
3. Click “Download & Install Simulator”

Creating the instance and item

Navigate to the “Instances” menu and click “Add new Instance”. 

Select the Simulator Connector from the drop-down menu and give it a fitting name. No other parameters are needed for this instance

Next we add a new item:

1. Click “New Item”
2. Give the item a fitting name
3. Set Min & Max to values you seem fit - we will be using 0 and 50 for this test
4. Click “Save Item”

You now have an item generating data for you, and is ready to be sent to your MQTT endpoint

Create a mapping 

Click on “New Mapping”. From here, fill out the needed information and click “Save mapping”

Validating the data exchange

With items and mappings created, data should now be streaming to your MQTT endpoint. 

To validate that data is in fact coming in, navigate to MQTT Explorer. When connected to the endpoint, you should see that data is coming in

Conclusion

Using SIA Connect and MQTT Explorer to test connections via a public MQTT endpoint is a straightforward process. By following the steps outlined in this guide, you can ensure that your MQTT client applications are correctly configured and capable of communicating with an MQTT broker. This setup is invaluable for developing and testing IIoT applications, ensuring reliable and efficient data transmission.