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

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

📤 Outputs

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

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

• 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

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

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

• 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

• 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.