Data Viewer

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Why Use the Data Viewer?

You need to see what data is flowing through your broker—which topics are active, what payloads look like, and how to send test messages. The built-in Data Viewer in the Coreflux HUB lets you subscribe to topics, browse the topic tree, and publish messages without installing an external MQTT client.

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When to Use It

• Viewing device data — Subscribe to sensor or device topics to see live readings (temperature, status, etc.) as they arrive
• Exploring your topic structure — Browse the Topic Tree to understand which topics exist and how they are organized
• Verifying Actions — Subscribe to output topics to confirm your LoT Actions are publishing correctly
• Debugging — Inspect payloads and topic structure in real time
• Testing — Publish messages to trigger Actions, test Connectors, or simulate device data
• Monitoring broker activity — Watch $SYS topics to check broker health, connected clients, and message throughput
• Listening to audio — Hear raw PCM on a topic, watch the waveform, and export a WAV clip

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Accessing the Data Viewer

1. In the HUB top navigation, select MQTT, then Data Viewer.
2. The Topic Tree appears on the left, showing topics as they receive messages.
3. Select a topic to view its payloads in the right panel.

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Topic Tree

The Topic Tree shows the hierarchical structure of topics. Topics appear as messages are received. Expand branches to navigate and select a topic to view its payload history in the payload viewer.

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Exploring Live Data

The Data Viewer is laid out as three vertical panels: Publish on the left, the Topic Tree in the middle, and a Detail area on the right where you build a personal view of the topics you care about right now. You can drag the divider between the tree and the detail area, and collapse the Publish panel into a thin rail to give yourself more room.

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Previewing a topic

Get a feel for what is happening on the broker without committing to a layout. Click any topic in the tree and its latest payload appears in the Detail area as a quick preview. Each row in the tree carries a small type icon that tells you at a glance what kind of value the topic currently holds: Rows briefly flash orange whenever a new message arrives, so you can see broker activity without staring at every value. To narrow the list, type any part of a topic path into the Filter box at the top of the tree — the filter matches anywhere in the path, and the usual display cap is lifted while you are filtering. For broader monitoring, you can also subscribe with a wildcard pattern such as sensors/#, and every matching topic appears in the tree as messages come in.

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Tracking what matters

Once a topic is worth watching, pin it: double-click the topic, or drag it from the tree onto the Detail area. A card appears for it, and the card shape adapts to the payload so you don’t have to mentally decode raw values:

• Numbers render as a large value with a sparkline of recent history — perfect for sensor readings like temperature or RPM.
• Booleans render as a glowing lamp — green when true, dim when false.
• JSON and text render with colored keys and an expandable tree, so nested objects stay readable.
• Geolocation payloads (latitude/longitude) render as a small map with the current point and a trail of recent positions, plus the raw payload underneath. The map uses OpenStreetMap tiles. In the dark theme those tiles are darkened, while the marker, the trail, and the © OpenStreetMap contributors attribution keep their own colours.

Cards can be reordered by dragging them up or down, copied to the clipboard with one click, and removed with the X in their corner. Add more topics any time from the dashed + Add topic button at the bottom of the cards, which opens a searchable list of every known topic.

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Replaying history with the timeline

As soon as you are tracking topics with more than one message of history, a timeline appears at the top of the Detail area. Every tracked topic gets its own color, and every message it has received is drawn as a colored mark on a horizontal track. From there you can:

• Click or drag anywhere on the track to scrub to a moment in time — every card below jumps to the values they had then.
• Step message-by-message with First / Previous / Next / Last.
• Hit Play to replay the message history like a video, with cards animating through every value.
• Tap Live to snap back to the latest message and resume real-time updates (the label turns green when you are caught up).
• Open the gear icon to change the history buffer per topic, from 50 up to 2 000 messages — larger buffers give you more scrub range.

While the viewer is focused, the arrow keys step through messages, Home jumps to the first, and End jumps back to live.

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Drilling into payloads

When a payload is too big to read inline, click its preview in the tree to open the payload inspector — a floating window that parses the full payload and lets you expand JSON to any depth. If the payload contains coordinates, the inspector draws the same OpenStreetMap map at the top. For payloads where you only care about one number, drag a single value out of the inspector (or out of a card’s expanded JSON tree) onto the Detail area. That value becomes its own extraction card — a small card that tracks just that one field, sparkline included if it’s numeric. It’s the fastest way to follow temperature from a 30-field sensor payload without the surrounding noise.

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Drag-and-drop cheatsheet

Most of the viewer is built around dragging. While you are dragging, valid drop zones light up so you can’t miss them.

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Publishing Messages

To publish a test message:

1. Click the Publish (paper plane) icon in the Data Viewer’s left rail to open the Publish panel.
2. Select or enter the target topic.
3. Enter the payload and pick its format (RAW, JSON, or XML), with optional QoS and Retain.
4. Click Publish to send the message.

Use this to trigger Actions, test connector configurations, or simulate device data.

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Listening to PCM audio

Some topics carry sound as raw bytes — the chunks an Audio Input connector publishes from a microphone, a tone, or a file. When the payload is that raw PCM, the detail area switches to an audio view. The viewer decides from the payload, not from the topic path. A topic named sensors/line1/status is audio if the bytes are PCM. A topic with audio in the path stays a normal text or JSON card when the payload is not PCM. From that view you can:

• Watch a live waveform as chunks arrive.
• Listen to the stream.
• Capture a stretch of audio and review it before you keep it.
• Export WAV of the captured clip.
• Scrub the timeline — the waveform, playback, and the other tracked cards stay on the same moment.

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Open the viewer in its own window

In the HUB, Open in a new window opens the Data Viewer in its own window on the broker you are already connected to.

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Next Steps