Getting Started

Creating a basic LoT Action in the VS Code extension — Deploy your first LoT Action from VS Code

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 — see the VS Code Setup Guide
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

VS Code Extension
MQTT Client

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 — Creating a new LoT Notebook 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 — Connecting to your Coreflux broker from 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 — Creating a new LoT code cell in the notebook

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

VS Code Extension
MQTT Client

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 — TemperatureSimulator action listed in the Coreflux Entities panel

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 MQTT Explorer 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 (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”.

VS Code Extension
MQTT Client

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 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:

VS Code Extension
MQTT Client

On the Coreflux Entities tab, right-click the desired action in your Actions list and select “Remove”.

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 VS Code extension 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

​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