# MQTT Subscribe (TLS-Beta)

This function block connects to an MQTT broker and listens for messages on a chosen topic using TLS (secure) connection options. It receives incoming text payloads and signals when new data has arrived so you can process or forward the data in your scenario.

## 📥 Inputs <a href="#inputs" id="inputs"></a>

`Enable` This boolean input socket controls whether the subscription is active. Set to TRUE to allow receiving messages; FALSE disables processing.

## 📤 Outputs <a href="#outputs" id="outputs"></a>

`Data` Text payload of the most recently received message.

`New Data` Boolean flag that becomes TRUE for a single evaluation when a new message has been received.

## 🕹️ Controls <a href="#controls" id="controls"></a>

`Server / Broker` Enter the MQTT broker address or hostname.

`Port` Set the broker port (common TLS port is 8883).

`Topic` Specify the topic to subscribe to. Incoming messages on this topic appear on the `Data` output.

`Client ID` Optional identifier for this client on the broker.

`Username` Optional username for broker authentication.

`Password` Optional password for broker authentication.

`Use TLS` Toggle to enable secure (TLS) connection mode.

`CA Certificate` Option to provide or reference a CA bundle for TLS certificate verification (the block supports system CA verification).

`Connect` A control to initiate or re-establish the connection with the current settings.

`Auto Reconnect` Toggle to automatically reconnect if the connection is lost.

Note: If the block provides a compact UI, some advanced options may be grouped or under an "Advanced" section.

## 🎯 Features <a href="#features" id="features"></a>

* Secure MQTT subscription with TLS support for encrypted communication.
* Live flagging of new messages via the `New Data` output so you can trigger downstream processing only when necessary.
* Flexible topic selection to subscribe to any valid MQTT topic.
* Connection parameters and basic authentication controls for most broker configurations.
* Graceful reconnect handling so temporary network glitches do not require manual intervention.

## 📝 Usage Instructions <a href="#usage" id="usage"></a>

1. Configure your broker details using the `Server / Broker`, `Port`, and authentication controls if needed.
2. Enter the topic you want to listen to in the `Topic` control.
3. Enable the block by sending TRUE to the `Enable` input or using the block’s UI connect control.
4. Read incoming text payloads from the `Data` output. Use the `New Data` output to trigger downstream blocks only when a fresh message arrives.
5. If you change connection parameters, use the `Connect` control (or toggle `Enable`) to apply them.

## 📊 Evaluation <a href="#evaluation" id="evaluation"></a>

When active, this function block maintains a subscription to the configured topic. On each run it outputs the latest received payload on `Data` and sets `New Data` TRUE only when a new message has arrived since the last evaluation.

## 💡 Tips and Tricks <a href="#tips-and-tricks" id="tips-and-tricks"></a>

* Use `Parse Data Dictionary` or `Data to JSON` after `MQTT Subscribe (TLS-Beta)` to convert incoming JSON text into structured values for further processing.
* If you want to log incoming messages, connect `Data` to `CSV Export` or `Data to JSON` then to an export block.
* Combine with `Debug Input` to print or inspect messages during setup.
* Use `Logic Input` or `Rising Edge` to trigger actions only when `New Data` becomes TRUE.
* For distributed scenarios, pair this block with `Data Write Global` / `Data Read Global` to share the latest message across separate branches of your scenario.
* If the message contains image references or encoded image data, send the decoded image to `Show Image` to preview it.
* When publishing responses or acknowledgements, use the corresponding `MQTT Publish (TLS-Beta)` block to send messages back to the broker.

## 🛠️ Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* Connection fails: Verify `Server / Broker`, `Port`, and network access. Ensure TLS port and firewall rules are correct.
* Authentication errors: Re-check `Username` and `Password` entries, and confirm broker ACLs.
* No messages appearing: Confirm the exact `Topic` string (wildcards and hierarchy matter) and that another client is publishing to it. Use a simple tester client to confirm.
* Unexpected message format: Use `Parse Data Dictionary` or `String Operations` to inspect and normalize payloads.
* TLS issues: If certificate verification fails, ensure the CA certificate bundle is available or use the system CA option. For troubleshooting only, try a non-TLS connection (if broker allows) to isolate the cause.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.augelab.com/function-blocks/input-output/communication/mqtt-subscribe-tls-beta.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.