Getting Started

Coreflux HUB overview screen with a 'Start here' arrow pointing to the first navigation icon in the bottom toolbar

Why This Guide?

This is the fastest way to validate your Coreflux setup: in under 15 minutes you’ll have a live LoT (Language of Things) Action running inside your broker—proof that your installation works and logic executes at the edge. New to Coreflux? Start with the Overview.

Like installing an app on your router instead of your phone. LoT Actions run directly inside the broker — your logic executes at the edge without an external script or server.

Prerequisites

Before you begin, ensure you have:

A running Coreflux Broker — See the Installation Guide if you haven’t set one up yet
VS Code with the LoT Notebooks extension or access to the Coreflux HUB in your browser — see the VS Code Setup Guide for the extension
Basic MQTT knowledge — Understanding of topics, publish/subscribe patterns

Ready? Here’s what you’ll build and deploy.

Your First LoT Action in 15 Minutes

Concept Refresher: You are about to write an action that lives and runs inside the broker, not on your laptop.

Let’s create a simulated temperature sensor that publishes a temperature reading every 5 seconds. You’ll see data on a topic as soon as you deploy—no external input required. This keeps the whole guide in a single “temperature monitoring” flow.

Understanding the Action

LoT Actions have three parts:

Definition — DEFINE ACTION <name>
Trigger — When to run (ON EVERY <time> or ON TOPIC "<topic>")
Logic — What to do (publish data, conditional logic, etc.)

Here’s what we’re building:

Temperature Simulator

DEFINE ACTION TemperatureSimulator
ON EVERY 5 SECONDS DO
    PUBLISH TOPIC "sensors/zone1/temperature" WITH "{\"temperature\": 72}"

Line	What it does
`DEFINE ACTION TemperatureSimulator`	Creates an action named “TemperatureSimulator”
`ON EVERY 5 SECONDS DO`	Sets a time-based trigger (runs every 5 seconds)
`PUBLISH TOPIC ... WITH "{\"temperature\": 72}"`	Publishes a JSON payload with temperature in Fahrenheit (72°F)

Quotes inside strings must be escaped with backslashes (e.g. "{\"temperature\": 72}").

For a complete reference on triggers, operations, and advanced patterns, see the Actions documentation.

Deploy the Action

Coreflux HUB
VS Code Extension
MQTT Client

If you run Coreflux via Docker with the Coreflux HUB enabled, you can deploy actions directly from the browser. See Coreflux HUB Overview for full documentation.

Open the HUB

In your browser, open http://localhost:8080 if the broker runs on your machine, or http://<broker-ip>:8080 using the IP address of the machine where the broker is running.

Go to LoT Editor

In the top navigation, select LoT, then LoT Editor, and open the Actions tab. Click + New Action.

Animated walkthrough of opening the LoT Editor, selecting the Actions tab, and clicking New Action

Paste the Action Code

Paste the following code (no -addAction prefix needed—the HUB handles registration):

DEFINE ACTION TemperatureSimulator
ON EVERY 5 SECONDS DO
    PUBLISH TOPIC "sensors/zone1/temperature" WITH "{\"temperature\": 72}"

Confirm Creation

You will see a confirmation and the action will appear in the Actions list. The action is now deployed and running on the broker.

The VS Code extension provides syntax highlighting, auto-completion, and real-time validation for LoT actions. See the LoT Notebooks Setup Guide for full installation and configuration details.

Ensure you have the LoT Notebooks extension installed

Open the extension panel, search for ‘LoT Notebooks’, and install.

Create a new LoT Notebook file

Click on File > New File…, give it it to a descriptive name (e.g., temperature-monitor).

Animated walkthrough of creating a new .lotnb file in VS Code

Connect to Your Broker

Enter your broker credentials (host, port, username, password) and click Connect.

Animated walkthrough of entering broker credentials and connecting in VS Code

Default Broker Credentials

If you haven’t changed your broker credentials, use these defaults:

Setting	Value
Host	`localhost` or your server IP
Port	`1883` (unencrypted) / `8883` (TLS)
Username	`root`
Password	`coreflux` (change immediately!)

Create a New Action

Create a new code block and add your code.

Animated walkthrough of creating a new code block

Paste the Action Code

DEFINE ACTION TemperatureSimulator
ON EVERY 5 SECONDS DO
    PUBLISH TOPIC "sensors/zone1/temperature" WITH "{\"temperature\": 72}"

Deploy

Click the Run Button on that specific cell to publish the action to your broker.

If you’re using any external MQTT client, publish to the system command topic:

Connect

Connect to your broker with your credentials.

Publish the Action

Publish the following to $SYS/Coreflux/Command:

-addAction DEFINE ACTION TemperatureSimulator
ON EVERY 5 SECONDS DO
    PUBLISH TOPIC "sensors/zone1/temperature" WITH "{\"temperature\": 72}"

Check the Response

Subscribe to $SYS/Coreflux/Command/Output — you should see:

Action 'TemperatureSimulator' added successfully

Note the -addAction prefix — this tells Coreflux to register the action definition that follows.

Verify It’s Running

Coreflux HUB
VS Code Extension
MQTT Client

If you deployed via the HUB, verify using the built-in Data Viewer. In the top navigation, select MQTT, then Data Viewer. In the Topic Tree, navigate to sensors → zone1 → temperature. You should see {"temperature": 72} arriving every 5 seconds in the payload viewer.

Coreflux HUB Data Viewer with the topic tree and live payload for a sensor temperature topic

The LoT extension automatically shows debug values for MQTT topics, so you can verify in two ways:

Check the Actions list

If the action appears in your Actions list under the Coreflux Entities tab, it should be running.

Check live values in the extension

After deploying, the extension automatically subscribes to the action’s topics and displays live MQTT messages. You should see temperature readings (e.g. {"temperature": 72}) on sensors/zone1/temperature arriving every 5 seconds.

Coreflux Entities panel in VS Code showing TemperatureSimulator under the Actions list

Subscribe to sensors/zone1/temperature. You should see temperature readings arriving every 5 seconds:

{"temperature": 72}

Congratulations! Your first LoT Action is live.

Example Real Scenario: Temperature Alarm

Now let’s create a reactive action that transforms sensor data and checks thresholds. This demonstrates data transformation and conditional logic—common patterns in industrial monitoring.

This action runs only when a message arrives on sensors/+/temperature. After you deploy it, you will see no output until something publishes to that topic—for example, the Temperature Simulator from the previous section (if both are running), or a manual publish from the HUB Data Viewer or any MQTT client.

Here’s what the action does each time a new temperature reading arrives:

Trigger — The action fires whenever a message is published to any topic matching sensors/+/temperature (e.g. sensors/zone1/temperature).
Extract — It reads the temperature value (in Fahrenheit) from the incoming JSON payload.
Convert — It transforms Fahrenheit to Celsius using the standard formula: (F − 32) × 5 / 9.
Decide — If the Celsius value exceeds 35 °C, it publishes an alert to alerts/high_temp. Otherwise, it publishes the normalized Celsius reading to sensors/normalized.

DEFINE ACTION TemperatureAlarm
ON TOPIC "sensors/+/temperature" DO
    SET "temp_f" WITH (GET JSON "temperature" IN PAYLOAD AS DOUBLE)
    SET "temp_c" WITH (({temp_f} - 32) * 5 / 9)
    IF {temp_c} > 35 THEN
        PUBLISH TOPIC "alerts/high_temp" WITH ("Alert: " + {temp_c} + "°C exceeds threshold")
    ELSE
        PUBLISH TOPIC "sensors/normalized" WITH {temp_c}

The {} denotes variable substitution, and expressions must be wrapped in parentheses. The + in the topic pattern is a single-level MQTT wildcard — it matches any value in that position (e.g. sensors/zone1/temperature, sensors/zone2/temperature).

Deploy and Test

Deploy this action using the same method as above (Coreflux HUB, VS Code extension, or MQTT client). Once deployed, use the steps below to verify reactive logic.

How to Test the Logic

The action subscribes to any topic matching sensors/+/temperature (e.g. sensors/zone1/temperature). It expects a JSON payload with a temperature key (Fahrenheit). It then converts to Celsius and either publishes an alert (if > 35°C) or the normalized value.

Role	Topic	Description
Input	`sensors/zone1/temperature`	Publish test payloads here (must match `sensors/+/temperature`)
Output (normal)	`sensors/normalized`	Receives the Celsius value when temperature is at or below 35°C
Output (alert)	`alerts/high_temp`	Receives the alert message when temperature exceeds 35°C (e.g. 95°F)

Sample payloads (copy-paste):

Below threshold — publish to sensors/zone1/temperature:
```
{"temperature": 77}
```
Expect: a message on sensors/normalized with the Celsius value (about 25).
Above threshold — publish to sensors/zone1/temperature:
```
{"temperature": 95}
```
Expect: a message on alerts/high_temp with text like “Alert: 35°C exceeds threshold”.

Coreflux HUB
VS Code Extension
MQTT Client

Deploy the Temperature Alarm action

In LoT → LoT Editor → Actions, create a new action or open an existing one, paste the Temperature Alarm code, and save. Confirm it appears in the Actions list.

Open the Data Viewer

Select MQTT → Data Viewer. In the Topic Tree, watch sensors/normalized and alerts/high_temp (add them to your tracked view if needed).

Coreflux HUB Data Viewer with the Publish panel on the left, Topic Tree in the center, and a tracked topic with live values on the right

Send test data

In the Publish panel, set the topic to sensors/zone1/temperature and paste one of the sample JSON payloads above. Click publish. If the Temperature Simulator is still running, it already publishes every 5 seconds—you will see results on sensors/normalized (72°F is below 35°C).

Confirm output

Select the output topic in the tree and verify the payload in the viewer (normalized value or alert text).

Deploy the Temperature Alarm action

Paste the action code in a LoT cell and run it. Confirm success in the Actions list.

Observe output topics

After deploying, the extension automatically subscribes to the action’s output topics and displays their values. Look for messages on sensors/normalized and alerts/high_temp once test data is published.

Send test data

Use the HUB Data Viewer, the VS Code extension publish tools, or any MQTT client to publish one of the sample JSON payloads above to sensors/zone1/temperature. If the Temperature Simulator from the previous section is still running, it already publishes every 5 seconds and you will see results on sensors/normalized (72°F is below 35°C). Check the topic tree displayed below the code cell to see incoming values update in real time.

Confirm output

Check that the corresponding output topic received the expected message (normalized value or alert).

Deploy the Temperature Alarm action

Publish the action to $SYS/Coreflux/Command with the -addAction prefix. Confirm “Action ‘TemperatureAlarm’ added successfully” on $SYS/Coreflux/Command/Output.

Subscribe to output topics

Subscribe to sensors/normalized and alerts/high_temp so you can see responses.

Publish a test payload

Publish to topic sensors/zone1/temperature with payload {"temperature": 77} or {"temperature": 95} (use one of the sample payloads above).

Confirm output

You should see a message on sensors/normalized (for 77°F) or on alerts/high_temp (for 95°F).

This confirms your broker transforms data and applies conditional logic in real time.

Clean Up (Optional)

To remove the test action:

Coreflux HUB
VS Code Extension
MQTT Client

In LoT → LoT Editor → Actions, select the action in the list and use the delete control. Confirm deletion—the action is removed from the broker immediately.

Animated walkthrough of selecting and deleting an Action in the LoT Editor

Publish to $SYS/Coreflux/Command:

-removeAction TemperatureAlarm

Quick Examples

Looking for inspiration? Check out the Language of Things Training Repository for common patterns like:

Topic-Based Triggers: Echo messages between topics
State Machines: Toggle switches and conditional logic
Event Counters: Track and aggregate system events

Language of Things Training

Explore a collection of ready-to-use LoT Action examples and templates.

Troubleshooting

Action not executing?

Verify the broker is running and you’re connected
Check $SYS/Coreflux/Command/Output for error messages
Ensure proper indentation in your LoT action (use consistent tabs or spaces)
Confirm the action appears in $SYS/Coreflux/Actions or in the HUB LoT Editor Actions list

Can't connect to the broker?

Verify the broker hostname/IP and port are correct
Check that port 1883 (or 8883 for TLS) is open
Confirm your username and password are correct
If using TLS, ensure certificates are properly configured

Messages not appearing on subscribed topics?

Verify you’re subscribed to the exact topic (including case sensitivity)
Check if any Rules are blocking access to the topic
Use wildcards (+ or #) to debug topic hierarchies

Next Steps

Now that you have a working setup, explore the core LoT components:

Actions

React to events and publish data. Create time-based automations or respond to topic changes.

Introduction to LoT

Understand the core concepts and architecture of the Language of Things.

Quick Start

Developing and Managing Coreflux

Coreflux MQTT Broker

LoT Language

Product Updates

Why This Guide?

Prerequisites

Your First LoT Action in 15 Minutes

Understanding the Action

Deploy the Action

Verify It’s Running

Example Real Scenario: Temperature Alarm

Deploy and Test

How to Test the Logic

Clean Up (Optional)

Quick Examples

Language of Things Training

Troubleshooting

Next Steps

Actions

Introduction to LoT

Quick Start

Developing and Managing Coreflux

Coreflux MQTT Broker

LoT Language

Product Updates

Documentation Index

​Why This Guide?

​Prerequisites

​Your First LoT Action in 15 Minutes

​Understanding the Action

​Deploy the Action

​Verify It’s Running

​Example Real Scenario: Temperature Alarm

​Deploy and Test

​How to Test the Logic

​Clean Up (Optional)

​Quick Examples

Language of Things Training

​Troubleshooting

​Next Steps

Actions

Introduction to LoT

Why This Guide?

Prerequisites

Your First LoT Action in 15 Minutes

Understanding the Action

Deploy the Action

Verify It’s Running

Example Real Scenario: Temperature Alarm

Deploy and Test

How to Test the Logic

Clean Up (Optional)

Quick Examples

Troubleshooting

Next Steps