MQTT Publish (TLS-Beta)

This function block sends data to an MQTT broker using optional TLS security. It provides settings for broker address, authentication, TLS mode, QoS, retain flag and keepalive—so you can publish formatted messages from your system to any MQTT topic.

📥 Inputs (sockets)

Enable Toggle to activate publishing. When this input is TRUE the block will attempt to send the provided data.

Data The data to publish. This generic socket accepts text or structured data (recommended to format as JSON or string).

📤 Outputs (sockets)

This function block does not produce any outputs.

🕹️ Controls

Broker Address Enter the MQTT broker host or IP address.

Port Enter the broker port. Common default is 1883.

Topic The MQTT topic to publish messages to.

Username Optional username for broker authentication.

Password Optional password for broker authentication (masked in the UI).

TLS Mode Selection Choose TLS behaviour. Options include None, Auto (use system/root certificate), and specific TLS versions with a custom certificate file.

Cert File Path Optional path to a .crt file when using custom TLS configuration.

Quality of Service Choose message delivery level (0, 1 or 2).

Keep alive (s) Set the keepalive interval in seconds.

Retain Switch to publish retained messages on the broker.

🎯 Key features

• Secure publishing with selectable TLS options, including auto certificate handling or custom certificate file.

• Authentication support with username/password.

• QoS and retain flags for delivery guarantees and persistent messages.

• Automatic reconnect attempts when connection is lost and simple status logging to help diagnose issues.

• Simple UI controls for all common MQTT parameters—no programming required.

📝 How to use

1. Fill Broker Address and Port to point to your MQTT broker.

2. Set Topic for the target messages.

3. If needed, provide Username and Password. Leave them empty for anonymous brokers.

4. Pick TLS Mode Selection. Use Auto for standard secure connections without supplying a certificate file, or provide Cert File Path if your broker requires a specific .crt file.

5. Configure Quality of Service, Keep alive (s) and enable Retain if you want messages stored on the broker.

6. Feed the data you want to send into the Data input. Use Enable to trigger sending (TRUE to enable).

7. Monitor logs shown by the block for connection and publish status.

📊 What happens when it runs

When enabled, the block verifies connection parameters and attempts to connect or reconnect to the broker if necessary. Once connected, it publishes the provided Data to the configured Topic using the selected QoS and retain settings. Connection problems and publish results are surfaced via the block’s status/log messages.

💡 Tips and Tricks

• Combine with Data to JSON to convert multiple data fields into a single JSON message suitable for IoT dashboards.

• Use String Merge when you want to build a custom text message (for example merging device id + status).

• Add Date-Time to include timestamps in your messages for logging or timeline plots.

• Trigger publishing on events by coupling this block with Logic Input or Rising Edge so messages are only sent when something meaningful happens.

• Use MQTT Subscribe (TLS-Beta) in a separate instance of the same block type to verify messages are received on the broker (handy for end-to-end checks).

• Before sending image-heavy data, consider using Image Logger or Image Write to save images locally and publish only metadata or a file path via MQTT to reduce bandwidth.

🛠️ Troubleshooting

• Connection failed: check Broker Address, Port, firewall and network reachability. Try a simple MQTT client to confirm broker is reachable.

• Certificate/TLS errors: switch TLS Mode Selection to Auto if you do not have a certificate file, or supply the correct Cert File Path when custom TLS is required.

• Authentication failure: verify Username and Password with your broker.

• Messages not visible on broker: confirm Topic, QoS and Retain settings; use MQTT Subscribe (TLS-Beta) to monitor the topic locally.

• Unexpected data format: preview or log your message before publishing using Debug Input, String Merge, or Data to JSON to ensure the format matches your subscribers’ expectations.