scadalink-design/test_infra_opcua.md

Test Infrastructure: OPC UA Server

Overview

The test OPC UA server uses Azure IoT OPC PLC, a simulated OPC UA server that generates realistic data. It is configured with custom nodes that match ScadaLink attribute patterns.

Image & Ports

• Image: mcr.microsoft.com/iotedge/opc-plc:latest
• OPC UA endpoint: opc.tcp://localhost:50000
• Web/config UI: http://localhost:8080

Startup Flags

--autoaccept            Accept all client certificates
--unsecuretransport     Enable plain (non-TLS) OPC UA connections for dev tools
--sph                   Show PLC heartbeat on console
--sn=5 --sr=10 --st=uint   5 slow-changing nodes (10s cycle, uint)
--fn=5 --fr=1 --ft=uint    5 fast-changing nodes (1s cycle, uint)
--gn=5                      5 stepping nodes
--nf=/app/config/nodes.json Custom node definitions
--pn=50000                  Listen port

Custom Nodes

The file infra/opcua/nodes.json defines a single ConfigFolder object (not an array) with a root "ScadaLink" folder containing four equipment subfolders. Tags match typical ScadaLink instance attribute patterns:

Folder	Tags	Types
Motor	Speed, Temperature, Current, Running, FaultCode	Double, Boolean, UInt32
Pump	FlowRate, Pressure, Running	Double, Boolean
Tank	Level, Temperature, HighLevel, LowLevel	Double, Boolean
Valve	Position, Command	Double, UInt32
JoeAppEngine	BTCS, AlarmCntsBySeverity, Scheduler/ScanTime	String, Int32[], DateTime

All custom nodes hold their initial/default values (0 for numerics, false for booleans, empty for strings, epoch for DateTime) until written. OPC PLC's custom node format does not support random value generation for these nodes.

Custom nodes live in namespace 3 (http://microsoft.com/Opc/OpcPlc/). Node IDs follow the pattern ns=3;s=<Folder>.<Tag> (e.g., ns=3;s=Motor.Speed). Nested folders use dot notation: ns=3;s=JoeAppEngine.Scheduler.ScanTime.

The browse path from the Objects root is: OpcPlc > ScadaLink > Motor|Pump|Tank|Valve|JoeAppEngine.

Verification

1. Check the container is running:

docker ps --filter name=scadalink-opcua

2. Verify the OPC UA endpoint using any OPC UA client (e.g., UaExpert, opcua-commander):

# Using opcua-commander (npm install -g opcua-commander)
opcua-commander -e opc.tcp://localhost:50000

3. Check the web UI at http://localhost:8080 for server status and node listing.

CLI Tool

The infra/tools/opcua_tool.py script provides a convenient CLI for interacting with the OPC UA server.

Install dependencies (one-time):

pip install -r infra/tools/requirements.txt

Commands:

# Check server status, namespaces, and endpoints
python infra/tools/opcua_tool.py check

# Browse the Objects folder (top-level)
python infra/tools/opcua_tool.py browse

# Browse a specific equipment folder
python infra/tools/opcua_tool.py browse --path "3:OpcPlc.3:ScadaLink.3:Motor"

# Read a tag value
python infra/tools/opcua_tool.py read --node "ns=3;s=Motor.Speed"

# Write a value to a tag
python infra/tools/opcua_tool.py write --node "ns=3;s=Motor.Running" --value true --type Boolean

# Monitor value changes for 15 seconds
python infra/tools/opcua_tool.py monitor --nodes "ns=3;s=Motor.Speed,ns=3;s=Pump.FlowRate" --duration 15

Use --endpoint to override the default endpoint (opc.tcp://localhost:50000). Run with --help for full usage.

Relevance to ScadaLink Components

• Data Connection Layer — connect to this server to test OPC UA subscription, read/write, and reconnection behavior.
• Site Runtime / Instance Actors — deploy instances with tag mappings pointing at these nodes.
• Template Engine — design templates with attributes matching the Motor/Pump/Tank/Valve folder structure.