Docs · NodeManagement

NodeManagement overview

What the NodeManagement service set is, why it's the gap UA-.NETStandard does not fill, and the test pattern this suite enables.

The OPC UA spec defines a NodeManagement service set — runtime modification of the address space. Four services:

Service	What it does
`AddNodes`	Create new nodes (Objects, Variables, Methods, …)
`DeleteNodes`	Remove nodes (optionally also their incoming references)
`AddReferences`	Add references between existing nodes
`DeleteReferences`	Remove references

These are the four services your client library calls to dynamically shape an OPC UA server's address space at runtime.

Why this suite exists

UA-.NETStandard — the reference stack uanetstandard-test-suite is built on — does not implement these services over the wire. You can call AddNodes on a client connected to any UA-.NETStandard server and get back Bad_ServiceUnsupported (or similar).

That's a problem for client libraries that:

Expose the NodeManagement API in their public surface.
Want integration tests that drive that API against a real server.
Want regression coverage for the wire-encoding of AddNodes payloads (which are non-trivial — ExtensionObject- laden, type-definition-aware).

open62541 implements NodeManagement fully. open62541-nm (port 24840) exposes it without security or auth getting in the way.

When NodeManagement actually matters

It's a less-common scenario than Read/Write/Subscribe. The typical use cases:

Use case	Why NodeManagement
Edge gateway dynamically modelling discovered devices	New devices → new node trees, on the fly
Configuration-driven server	Operator changes config → server reshapes itself
Test fixture creation	Test creates nodes, runs assertions, deletes them
Wire-spec validation	Verify the `AddNodes` payload encoder round-trips

The first two are real production scenarios. Most production clients don't need NodeManagement — they consume an address space someone else built.

The test pattern

The canonical test against open62541-nm:

1. Connect to opc.tcp://localhost:24840 (anonymous, no security).
2. AddNodes — create the fixture(s) the test needs.
3. Exercise feature under test (browse, read, write, call, subscribe).
4. Assert.
5. DeleteNodes — clean up (or leave for the next test).
6. Disconnect.

The address space is empty at connect time. Tests bring their own data.

What you can create

NodeClass	Use case
`Object`	A folder or grouping in the address space
`Variable`	A typed value (with `DataType` + `ValueRank`)
`Method`	A callable method
`ObjectType`	Define a new type for instantiation
`VariableType`	Define a new variable type
`ReferenceType`	Define a new reference type
`DataType`	Define a custom data type
`View`	Define a filtered browse view

Object, Variable, and Method are the most common in practice.

What you can reference

A new node typically uses one of these reference types between it and its parent:

ReferenceType	Used between
`Organizes`	Folder → folder, folder → leaf
`HasComponent`	Object → child variable / child object
`HasProperty`	Variable → property (e.g. EURange)
`HasTypeDefinition`	Instance → its TypeDefinition

For the standard reference type NodeIds (ns=0;i=35 for Organizes, etc.) see the OPC UA spec or your client library's constants.

A complete round-trip

1. Connect.

2. AddNodes (one node):
   - parentNodeId:    ns=0;i=85   (Objects folder)
   - referenceTypeId: ns=0;i=35   (Organizes)
   - requestedNewNodeId: ns=1;s=my-folder
   - browseName:      1:MyFolder
   - nodeClass:       Object

3. Browse(ns=0;i=85) → expect "MyFolder" in results.

4. AddNodes (one variable, child of MyFolder):
   - parentNodeId:    ns=1;s=my-folder
   - referenceTypeId: ns=0;i=47   (HasComponent)
   - requestedNewNodeId: ns=1;s=my-folder.my-value
   - browseName:      1:MyValue
   - nodeClass:       Variable
   - dataType:        Int32
   - value:           42

5. Read(ns=1;s=my-folder.my-value) → 42.

6. Write(ns=1;s=my-folder.my-value, 99) → Good.

7. Read(ns=1;s=my-folder.my-value) → 99.

8. DeleteNodes([ns=1;s=my-folder.my-value, ns=1;s=my-folder]).

9. Browse(ns=0;i=85) → "MyFolder" no longer present.

10. Disconnect.

Every step is a separate test assertion.

Behaviour notes

Empty namespace. ns=1 is the writable test namespace — use it for all your test nodes. The server doesn't enforce this (ns=2..N also work) but ns=1 is the convention.
requestedNewNodeId may be ignored. The server can choose its own NodeId and return it in the response. The example test above assumes the request is honoured (which open62541-nm does in practice).
Cleanup is your responsibility. The server doesn't auto-purge nodes between sessions. A test that creates nodes and doesn't delete them leaves them for the next test.

Where to read next

Services reference — the four services' wire signatures and inputs.
open62541-nm — the server itself.

Last updated · 2026-05-25

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