node-red-contrib-opcda-recon 0.1.0

Windows OPC DA nodes for Node-RED backed by a native Node-API addon.

npm install node-red-contrib-opcda-recon

node-red-contrib-opcda-recon

Node-RED nodes for Windows OPC DA access through a native COM/DCOM addon.

This package provides discovery, status, browse, sync/async read, batch sync read, sync/async write, and OPC DA data-change subscriptions.

Screenshots

Paged OPC item browser with multi-select support:

Node-RED flow using OPC DA browse/read nodes:

Current scope

• Windows only
• x64 only
• Native raw Node-API addon
• No node-addon-api dependency
• No shelling out to opcclient-recon.exe
• OPC DA 2.0 style COM/DCOM access

Nodes

• opcda connection: shared endpoint config and optional credentials
• opcda discover: lists OPC DA servers from OPCEnum
• opcda status: calls IOPCServer::GetStatus
• opcda browse: browses item IDs
• opcda browse paged: editor-side paged item picker for long flat item lists
• opcda read: reads one item ID
• opcda read batch: synchronously reads many item IDs in chunks
• opcda subscribe: emits OPC DA data changes
• opcda write: writes one item value

The write node has a two-key safety guard:

1. The editor checkbox Enable writes must be enabled.
2. The incoming message must set msg.allowWrite === true.

Build

From this package directory:

npm install
npm run build

I did not run installation automatically. You can run those commands yourself when you are ready.

The build expects the OPC Foundation headers in the usual OPC Core Components Redistributable path:

C:\Program Files (x86)\Common Files\OPC Foundation\Include

If your headers are elsewhere, update binding.gyp.

Local Node-RED usage

From your Node-RED local directory:

cd <node-red-user-dir>
npm install <path-to-node-red-contrib-opcda-recon>

Then restart Node-RED and look for the OPC DA Recon nodes in the palette.

Message shapes

Most node settings can be overridden by message properties.

Discover

msg.host = "opc-server-host"; // optional; defaults to localhost

Returns:

msg.payload = {
  host,
  servers: [
    { progId, clsid, description }
  ]
};

Status

msg.progId = "Kepware.KEPServerEX.V6";

Returns server state, vendor info, timestamps, group count, and bandwidth where available.

Browse

msg.progId = "Kepware.KEPServerEX.V6";
msg.limit = 50; // optional

Returns:

msg.payload = {
  host,
  progId,
  namespaceType,
  items: ["Channel1.Device1.Tag1"]
};

Paged browse picker

Use opcda browse paged when a server has thousands of flat item IDs.

In the node editor:

• choose a deployed OPC DA connection
• enter the ProgID
• optionally enter a server-side item-name filter
• choose page number and items per page
• click Load / Refresh, Previous, Go, or Next
• check one or more items to select them across pages
• use Clear Selection to de-select everything selected so far

The editor shows the native browse strategy:

• IOPCBrowse continuation paging when the server supports IOPCBrowse
• Flat enumerator cache fallback when the plugin falls back to enumerating and caching the flat list

On input, the selected items are emitted:

msg.progId = "Kepware.KEPServerEX.V6";
msg.itemIds = [
  "Channel1.Device1.Tag1",
  "Channel1.Device1.Tag2"
];
msg.payload = {
  progId: "Kepware.KEPServerEX.V6",
  itemIds: [
    "Channel1.Device1.Tag1",
    "Channel1.Device1.Tag2"
  ]
};

The first selected item is also emitted as msg.itemId for older single-read flows.

Read

msg.progId = "Kepware.KEPServerEX.V6";
msg.itemId = "Channel1.Device1.Tag1";
msg.mode = "sync"; // or "async"

Returns one result with value, quality, timestamp, access rights, and data type metadata.

Batch sync read

opcda read batch reads many item IDs using one OPC group and one synchronous IOPCSyncIO::Read call per chunk.

msg.progId = "Kepware.KEPServerEX.V6";
msg.itemIds = [
  "Channel1.Device1.Tag1",
  "Channel1.Device1.Tag2"
];
msg.chunkSize = 500; // optional, native addon clamps to 1..1000

Returns:

msg.payload = {
  host,
  progId,
  count,
  successCount,
  failureCount,
  chunkSize,
  results: [
    {
      itemId,
      success,
      value,
      variantType,
      quality,
      qualityRaw,
      timestamp,
      error,
      canonicalType,
      accessRights
    }
  ]
};

Result order matches the input itemIds order. Invalid item IDs are reported as failed result rows when the server returns per-item errors.

Subscribe

The subscribe node is a source node. It starts when the flow is deployed and stops on redeploy or shutdown.

Configure:

ProgID: Kepware.KEPServerEX.V6
Item IDs:
  Channel1.Device1.Tag1
  Channel1.Device1.Tag2
Update ms: 1000

Each changed item emits:

msg.topic = "Channel1.Device1.Tag1";
msg.payload = value;
msg.opcda = {
  host,
  progId,
  itemId,
  value,
  variantType,
  quality,
  qualityRaw,
  timestamp,
  error,
  success,
  revisedUpdateRateMs
};

Subscriptions require reverse DCOM callback access from the OPC server back to the Node-RED host. If the node reports Advise(IOPCDataCallback) errors such as 0x80070533, discovery/read may still work because they only require outbound DCOM, but subscriptions will need target/client DCOM callback security fixed.

Write

msg.progId = "Kepware.KEPServerEX.V6";
msg.itemId = "Channel1.Device1.Tag1";
msg.value = 123;
msg.mode = "sync"; // or "async"
msg.allowWrite = true;

The node will reject the message unless allowWrite is exactly true and the node's Enable writes checkbox is checked.

Quick load test

After building:

npm run test:load

This only checks that the native addon loads and exports the expected functions.

Native direct tests

These tests call build\Release\opcda_recon.node directly from Node.js and bypass the Node-RED runtime/UI.

Fast validation tests do not require a live OPC server:

npm run test:native:validation

Run load + validation together:

npm run test:native

Run the simple native runtime-argument example:

npm run test:hello -- xxx

This calls addon.helloWorld("xxx") and expects Hello World xxx.

Live OPC/DCOM smoke tests require environment variables:

$env:OPCDA_TEST_HOST = "192.0.2.10"
$env:OPCDA_TEST_DOMAIN = "DOMAIN"
$env:OPCDA_TEST_USERNAME = "username"
$env:OPCDA_TEST_PASSWORD = "password"
$env:OPCDA_TEST_PROGID = "Kepware.KEPServerEX.V6"
$env:OPCDA_TEST_ITEM1 = "Channel1.Device1.Tag1"
$env:OPCDA_TEST_ITEM2 = "Channel1.Device1._System._ScanRateMs"

npm run test:native:live

The live test covers validateConnection, discover, status, browse, browsePage, sync read, and readBatch. It also checks that flat browse cache is reused when Items/page changes.

Optional tests are disabled unless explicitly enabled:

$env:OPCDA_TEST_ASYNC = "1"
$env:OPCDA_TEST_SUBSCRIBE = "1"

$env:OPCDA_TEST_WRITE = "1"
$env:OPCDA_TEST_WRITE_ITEM = "safe.writable.test.tag"
$env:OPCDA_TEST_WRITE_TYPE = "i4"
$env:OPCDA_TEST_WRITE_VALUE = "123"

Only enable write tests against a safe writable test tag.