Process data, Publish it and Subscribe to a topic

In this tutorial, you will learn how to process data, publish to a topic, and subscribe to it. The tutorial uses the MQTTX client throughout.

Connecting to TagoIO MQTT Broker​

To publish a topic via TagoIO's MQTT, you must first add a device.

• Navigate to the Devices module in your Admin panel and create a new device. You may choose any connector you prefer; it will not make a difference.
• After creating the device, open the device’s General Information tab and locate the tokens section.
• Copy your device token from the tokens section — this token is required to authenticate when publishing or subscribing via the TagoIO MQTT broker.

Open MQTTX and create a new connection

Subscribing to a topic​

1. In MQTTX, go to the Subscribe tab.
2. Type sensor/output in the Topic field and click Subscribe.
3. You should now see any messages that are published on this topic appear in the client.

Processing the data​

In this step we create an analysis that converts temperature from Fahrenheit to Celsius and publishes it on the topic sensor/output. The analysis is triggered whenever a message is received on the topic sensor/input.

Note: Replace "DEVICE_ID" with your actual device ID. You can obtain this ID by accessing your device's page and copying it from the URL, for example: https://admin.tago.io/devices/652425f4516e99000a522dce.

const { Analysis, Services } = require("@tago-io/sdk");

const DEVICE_ID = "YOUR_DEVICE_ID"; // Replace with your actual device ID

async function mqttPushExample(context, scope) {
  console.log(context, scope);
  if (!scope.length) {
    return context.log("Missing values");
  }

  const myData = scope.find((x) => x.variable === "payload") || scope[0];
  if (!myData) {
    return context.log("Couldn't find any variable in the scope.");
  }

  // Create your data object to push to MQTT
  const myDataObject = {
    variable: "temperature_celsius",
    value: (myData.value - 32) * (5 / 9),
    unit: "C",
  };

  // Options for publishing
  const options = {
    retain: false,
    qos: 0,
  };

  // Publishing to MQTT
  const mqtt = new Services().mqtt;
  await mqtt.publish({
    device: DEVICE_ID,
    message: JSON.stringify(myDataObject),
    topic: "sensor/output",
    options,
  });
}

module.exports = new Analysis(mqttPushExample);

Permissions

This analysis requires permission to send MQTT data to the device. Enable this access in the Access Management module by creating a new Policy.

Creating an Action

1. Go to the Actions module and create a new action.
2. Set:
   • Name: Any name
   • Type of Trigger: MQTT Topic
   • Trigger: sensor/input
   • Device: The device you created earlier
3. For the action type, choose Run Analysis and select the analysis you just created.
4. Click Create my Action.

Now, whenever a message is published on the topic sensor/input, the analysis will run, convert the temperature to Celsius, and publish it to sensor/output. You can test this by publishing the value 32 on sensor/input using MQTTX; the converted value should appear in the client.