MarcandCopilot
6d57355eea
A review against the OPC UA Data Channels errata found five defects. Four are implementation faults; two of them also exposed gaps in the draft, which are proposed separately in the drafts repository. Validate transportChannelId where the result is visible (Part 6 7.4) QuicServerDataChannelTransport.BindClientStreamAsync discarded the task carrying every 7.4 check, so a Client could name the control stream, a stream it did not initiate, or one already bound, and the Server answered Good and echoed the value. The checks were right; nothing consumed them. Validation and stream reservation now run inline where a refusal becomes the Service result. Only the wait for the stream to materialize stays deferred, because a peer-initiated QUIC stream is observable only once the peer writes to it and a Client writes only after it has the response - awaiting it would deadlock the exchange rather than order it. Stop one unread channel stalling the SecureChannel (Part 6 5.8) The delivery queue was bounded in frames but sized from a byte credit, and it blocked when full. Small frames therefore filled it long before credit ran out, and the block landed on the reader that also carries MSG, OPN and CLO, so a slow consumer on one channel stalled every Session, Subscription and Publish on the connection - the opposite of "stalls that stream and nothing else". The queue is now bounded by encoded frame bytes, as 7.4 bounds the unknown-ChannelId buffer and for the same reason, and a peer that exceeds the bound is reset rather than waited on. This also removes a sync-over-async violation. Open the channel when the response is dispatched, not before (Part 4 5.1) OnResponseSent ran before the response object was encoded, so MarkOpen could wake the scheduler and put a frame for a ChannelId on the wire ahead of the response naming it. SecureChannelContext gains an optional ResponseDispatched callback that both listeners invoke after handing the response to the transport; it is inert when unset. The scheduler additionally refuses to serve a channel still Opening, which is what the 5.13 state table already said. Carry inline data channels instead of discarding them (Part 6 5.16) A Server advertised opc.tcp, accepted OpenDataChannel, and then dropped every frame through a transport whose send path did nothing - the silent drop 5.16 forbids. InlineServerDataChannelTransport resolves the UASC channel behind the request and enables the engine on it, so channels ride the connection the Client already holds. A SecureChannel that can carry no frames is now refused with Bad_DataChannelTransportUnsupported. Give Uncertain_DataDiscarded its own identifier It shared identifier 1111 with Bad_DataChannelFrameTypeUnsupported. The two differ only in severity bits, so the collision produced valid but wrong constants instead of a build error; it is now 1113. The generator fails on a duplicate identifier and a test asserts the emitted constants are unique. Every regression test added here goes through the production entry point rather than the component, because that is precisely what the existing component-level tests missed in all four wiring defects. Opc.Ua.Core.DataChannels.Tests 284 pass on net10.0 and 212 on net48; Opc.Ua.Server.Tests 4072 pass; Opc.Ua.Sessions.Tests 776 pass with test discovery unchanged. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 5d026b47-265d-4c97-8715-26e207dfa03c
OPC UA .NET Standard Stack
🆕 This is version 2.0 of the OPC UA .NET Standard Stack (current
master).Looking for the supported 1.x release? It lives on the
master378branch (last release:1.5.378). All new feature work happens here onmaster;master378continues to receive security and critical-bug fixes for the 1.x line.
The official OPC Foundation reference implementation of OPC UA for .NET — a certified, cross-platform stack with client, server, PubSub, GDS, complex types, and source-generated tooling. Used in production across industrial control, manufacturing, energy, and IoT systems.
📦 What it is
- A full-stack OPC UA implementation — Core / Client / Server / PubSub / GDS / LDS / Complex Types / Device Integration / Positioning libraries built on .NET, with UA-TCP and HTTPS transports.
- Cross-platform — runs on .NET 10, .NET 9, .NET 8 (LTS), .NET Framework 4.8, and .NET Standard 2.1; ships Native-AOT-friendly assemblies.
- Certified for compliance — the reference server has been certified through an OPC Foundation Certification Test Lab and is continuously verified against the latest Compliance Test Tool (CTT).
- Companion-spec coverage — Part 9 (Alarms & Conditions), Part 11 (Historical Access), Part 13 (Aggregates), Part 16 (State Machines), Part 17 (Alias Names), Part 18 (Role Management), Part 20 (File Transfer), Part 100 (Device Integration), Parts 210/211 (Relative Spatial Location and Global Positioning), OPC-10030 (ISA-95 Common Model) with OPC-10031-4 Job Control V1/V2, OPC 10100-1 (WoT Connectivity), OPC 40001-1 (Industrial Automation), OPC 40010-1 (Robotics).
- Modern developer surface — first-class
Microsoft.Extensions.DependencyInjectionhosting (services.AddOpcUa()), fluent server + client builders, source-generated NodeManagers and DataTypes, and an MCP server so LLMs / Copilot can drive an OPC UA client.
For the full feature breakdown see OPC UA Profiles and Facets and the What's New in 2.0 tour.
🚀 Getting started
You need the .NET 10 SDK to build the repo. From the repository root:
dotnet restore UA.slnx
dotnet build UA.slnx
For the supported target frameworks and platform notes see
the Developer Guide. The official NuGet packages
are published to nuget.org under the OPCFoundation.NetStandard
prefix — the meta package
OPCFoundation.NetStandard.Opc.Ua
pulls in everything, or pick the split
OPCFoundation.NetStandard.Opc.Ua.Core / .Client / .Server /
.Bindings.Https packages directly. Preview builds for every successful
master build are available in the
Azure DevOps opcua-preview feed.
Sample applications
Each sample has its own README.md with build and run instructions.
Reference applications
- Console Reference Server — the certified reference server (with Quickstarts, CTT, and Mono configs). Also ships as a Docker container.
- Console Reference Client — cross-platform reference client demonstrating sessions, subscriptions, browsing, and method calls.
- Console LDS Server — a standalone
Local Discovery Server built on
Opc.Ua.Lds.Server.
PubSub samples
- Console Reference PubSub Client —
one executable with
publisher,subscriber, andexternal(external-server adapter) modes across the supported transport profiles.
Minimal / Device-Integration samples
- Minimal Calc Server — minimal server built on the source-generated NodeManager pipeline (Calc model).
- Minimal Boiler Server — minimal Boiler-model server with the fluent state-machine builder; Native-AOT publishable.
- Pump Device Integration Server —
minimal Device Integration (Part 100) server using
Opc.Ua.Di.Server's fluent builder. - Minimal Robot Server — OPC 40010 Robotics with independently configurable RSL/GPOS motion and live OpenUSD transforms.
- Intent Enabled Robot — one collaborative arm exposing the draft Robot Intent command surface: task-level motion verbs tracked on a Part 10 program lifecycle, with missions, command authority and safety-aware refusal.
- Intent Viewer Client — click a target in an OpenUSD viewport and watch the arm execute the resulting intent; also runs headless.
- Minimal ISA-95 Server — minimal server hosting the OPC-10030 ISA-95 Common Model together with OPC-10031-4 Job Control V1 and V2, using the typed common-model builder and the in-memory Job Control provider.
More sample projects are maintained in the companion OPC UA .NET Samples repository.
Developer tools
- OPC UA MCP Server — installable .NET tool and container that exposes OPC UA client operations as MCP tools for LLMs and Copilot. The tools also ship as libraries (
…Opc.Ua.Mcp.Core,.PubSub,.Diagnostics,.PubSub.Diagnostics) so an application can embed them next to its own MCP tools.
🔧 Migrating from 1.5.378 to 2.0
The 2.0 release introduces breaking API changes, and comes with a full prescriptive migration guide that links to per-area documentation covering telemetry, packages, source generation, types, encoders, node states, identity, certificates, configuration, sessions / subscriptions, alarms / model change, and TimeProvider.
Most of the mechanical migration work is automated:
OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzerNuGet — install it in your project to get analyzer warnings (UA0001–UA0022)- one-click code fixes for the patterns in the guide. Setup steps are in the package's NugetREADME.md.
- Migration agent skill — the
opcua-v20-migrationskill walks Copilot / Claude / any coding agent through installing the NuGet, runningdotnet format analyzersto apply auto-fixes, and handling the small residual manual patterns. The skill knows which sub-doc to load for each symptom so it stays context-efficient.
If you are still on 1.x and not ready to upgrade, stay on the
master378
branch — it continues to receive security and critical-bug fixes.
🤝 Contributing and license
Community contributions are welcome. Fork the repository, make your changes on a branch, and open a pull request; see CONTRIBUTING.md for the contribution workflow.
Contributors must sign the OPC Foundation Contributor License Agreement (CLA). The CLA "I AGREE" gate is presented automatically on your first PR.
The project is licensed under the OPC Foundation MIT License. Report security vulnerabilities via the process documented in SECURITY.md.
📚 Further reading
- Documentation index — every per-feature doc with a one-line description.
- What's New in 2.0 — narrative tour of the 1.5.378 → 2.0 changes grouped by theme and layer.
- OPC UA Profiles and Facets — facets / transports / security policies the stack implements.
- Migration Guide — prescriptive
per-version migration reference (links to
docs/migrate/2.0.x/). - OPC UA Online Reference — the official OPC 10000 series specification index.
- OPC UA .NET Samples — companion repository with more sample applications.
- Preview NuGet feed — prerelease builds from Azure DevOps.