Flows (Node-RED) — Getting Started
The /ui/flow menu gives you access to the Node-RED environment built into the gateway.
Node-RED is a low-code tool where you build data flows by dragging and dropping blocks (nodes) and wiring them together. You can read and write gateway tag values, integrate with external systems over MQTT/HTTP, and design automation such as alarms, logging, and calculations.
Node-RED 4.1.10 + Node.js 20 (both installed globally inside the image). On the container's first boot, userDir.seed
(image-baked default flows + node_modules + plantpulse-edge / node-red-contrib-opcua nodes) is
automatically copied to /data1/pp-data/node-userdir/ (from the second boot onward, user flows are preserved).
User flows also survive an image upgrade.
The PlantPulse-specific nodes (pp-tag-value-read / pp-tag-value-write / pp-opc-* / pp-tag-list)
link to node/conf/plantpulse-edge-nodes/ in the image via absolute-path symlinks — the entrypoint guarantees this on every
boot (preventing the issue where the old native relative-path symlinks broke inside the container).
Finish through 자주 하는 작업 → 새 PLC 연결 추가 / 태그 등록 and start with at least one tag being collected in real time. Node-RED uses that tag value as its input.
1. Access
Connect to the gateway in a browser, then go to Flows (Node-RED) in the left menu, or navigate directly to http://<gateway>/ui/flow.
2. Screen layout
| Area | Description |
|---|---|
| Left palette | List of available nodes, sorted by category. The 엣지 category contains the gateway-specific nodes. |
| Center workspace | Drag nodes into place and connect them with wires. Can be split into tabs (multiple flows). |
| Right sidebar | The info tab shows help for the selected node; the debug tab shows the output log of debug nodes. |
| Top-right Deploy | You must press the Deploy button for your changes to actually take effect. |
3. Basic operations — handy shortcuts
| Action | How |
|---|---|
| Add a node | Drag from the palette into the workspace |
| Configure a node | Double-click the node → edit in the right panel → Done |
| Connect nodes (wire) | Drag from a node's output port (right side) onto another node's input port (left side) |
| Remove a wire | Click the wire to select it, then Delete |
| Multi-select | Shift drag to select an area, or Ctrl/Cmd + 클릭 to add to the selection |
| Copy / paste | Ctrl/Cmd + C / Ctrl/Cmd + V |
| Search | Ctrl/Cmd + F — search node names in the palette |
| Import a flow | Menu → Import → paste JSON (the example code in this document can be imported as-is) |
Even if you add, delete, or modify nodes, the gateway knows nothing about the change until you press Deploy. A node marked with a red dot (●) means "has unsaved changes."
4. Basic structure of a message (msg)
The data flowing between nodes is always a JavaScript object called msg. The most commonly used fields:
| Field | Meaning |
|---|---|
msg.payload | The body (main data). Can be a number, string, object, or buffer |
msg.topic | Topic (classification label). Frequently used in MQTT/Switch/Join, etc. |
msg.timestamp | Timestamp (fill it in yourself when needed) |
msg._msgid | A unique ID assigned automatically by Node-RED — for tracing |
Most nodes operate using msg.payload alone.
5. Edge nodes — at a glance (gateway-specific)
The 엣지 category in the left palette contains two nodes registered by the gateway itself. They are the input/output of nearly every IIoT flow.
| Icon | Node | English name | Behavior | REST called |
|---|---|---|---|---|
| ⬇ | Read tag value (pp-tag-read) | read tag value | Retrieves the current value of one tag (from cache or by reading the PLC directly) | GET /api/v1/tag/{tagId}/value |
| ⬆ | Write tag value (pp-tag-write) | write tag value | Writes a value to one tag (applied to the PLC immediately) | POST /api/v1/tag/{tagId}/value |
inject (1s) ──▶ 태그값 읽기 ──▶ 처리 (function/switch/...) ──▶ 태그값 쓰기 / mqtt out / debug / file ...
How to find the nodes — type read tag or 엣지 in the palette search box → only those two nodes are shown. They are a light pastel blue.
| Fields often left blank in node settings | How to fill them dynamically |
|---|---|
| Tag ID | Specify dynamically with msg.tagId = 'TAG_...' during the flow (reuse one node for multiple tags) |
| Value (write node) | Fill in during the flow with msg.value or msg.payload |
Before applying writes directly to live equipment, validate thoroughly with an external simulator or a test tag. Grant write permission only for tags agreed upon with the operations team.
For detailed fields / inputs and outputs / the full protocol support table → Edge category (tag read/write)
6. Your first flow — Hello World
Goal: read one tag every 5 seconds and print it to the Debug sidebar.
- Drag an
injectnode from the palette → double-click →Repeat: intervalevery 5 seconds→ Done - Drag a
엣지→태그값 읽기node → enter a real tag in Tag ID (e.g.,TAG_TEST_00042) → Done - Drag a
debugnode from the palette - Wire the three nodes together in
inject → 태그값 읽기 → debugorder - Click Deploy at the top right
- Open the debug tab in the right sidebar and check that a value is printed every 5 seconds
This pattern (periodic trigger → read → process) is the basic form of every IIoT flow.
7. Next steps
In left-menu order:
- Using the basic nodes — what the 14 nodes most used in IIoT do
- Edge nodes (tag read/write) — gateway-specific nodes (the detailed version of the at-a-glance section 5 above)
- MQTT nodes in detail — Broker settings / Pub / Sub / LWT / Birth
- OPC-UA nodes in detail — Endpoint / Item / Client / Subscribe / Browse
- Sparkplug B nodes in detail — Group / Edge / Birth-Death / send and receive
- IIoT example collection — 12 patterns frequently built in the field
- Troubleshooting — common pitfalls
8. Learn more
- The OPC-UA node viewer (
/ui/opcua) shows every tag/value/node ID the gateway currently holds at a glance. → Using the OPC-UA node viewer - The REST API itself is covered in the
고급 / 통합 파트너용 → REST APIchapter. Node-RED'spp-tag-read/pp-tag-writeare thin wrappers around that API. - Official Node-RED manual:
<https://nodered.org/docs/>