# OPC Foundation UA .NET Standard Reference Server

## Additional samples

- [OPC 10000-21 onboarding registrar/client](Gds/README.md) — loads the
  generated Onboarding companion model, binds the standard registrar
  administration methods to an injected ticket store, and drives a secure
  register/unregister round trip with a PowerShell script.

## Introduction

This document is referring to the CTT version 1.04.9.398.

This OPC Server is designed to be the default OPC UA Server when opening the [OPC UA Compliance Test Tool](https://opcfoundation.org/developer-tools/certification-test-tools/opc-ua-compliance-test-tool-uactt/) and it uses an address-space that matches the design of the UACTT and the requirements for OPC UA compliance testing.

It uses the OPC Foundation UA .NET Standard Library. Therefore it supports both the opc.tcp and https transports. There is a .NET framework based server with UI and a .NET Core console version of the server which runs on any OS supporting .NET 8.0 and later.

## How to build and run the Windows OPC UA Reference Server with UACTT

1. Open the solution **UA.slnx** with Visual Studio 2026.
2. Choose the project `Reference Server` in the Solution Explorer and set it with a right click as `Startup Project`.
3. Hit `F5` to build and execute the sample.

## How to build and run the console OPC UA Reference Server on Windows, Linux and iOS

This section describes how to run the **ConsoleReferenceServer**.

Please follow instructions in this [article](https://aka.ms/dotnetcoregs) to setup the dotnet command line environment for your platform. 

## Start the server

1. Open a command prompt.
2. Navigate to the folder **samples/Reference/ConsoleReferenceServer**.
3. To run the server sample type `dotnet run --project ConsoleReferenceServer.csproj`. The server is now running and waiting for the connection of the UACTT.

## UACTT test certificates

The reference server always rejects new client certificates and requires that the UACTT certificates are in appropriate folders.

- The console server certificates are stored in **%LocalApplicationData%/OPC Foundation/pki**.
- The Windows .NET framework server stores the certificates in **%CommonApplicationData%\OPC Foundation\pki**.
  - **%CommonApplicationData%** maps to the path set by the environment variable **ProgramData** on Windows.
  - **%LocalApplicationData%** maps to a hidden location in the user home folder and depends on the target platform. See [Certificates](Certificates.md) for more information.

### Certificate stores

Under **pki**, the following stores contain certificates under **certs**, CRLs under **crl** or private keys under **private**.

- **own** contains the reference server public certificate and private key.
- **rejected** contains the rejected client certificates. To trust a client certificate, copy the rejected certificate to the **trusted/certs** folder.
- **trusted** contains *trusted* client and CAs certificates and CRLs.
- **issuer** contains CAs certificates and CRLs needed for validation.
- **trustedUser** contains *trusted* user and user CA certificates and CRLs.
- **issuerUser** contains user CA certificates and CRLs needed for validation of the certificate chains.

### Placing the UACTT certificates

CTT creates a **PKI** folder in a new project. There is a subfolder **copyToServer** which contains the application and user identity certificates.
Copy the **ApplicationInstance_PKI** certificates for testing with the UACTT to the following stores:

- **trusted/certs**: trusted certificates
- **trusted/crl**: revocation lists of trusted certificates
- **issuer/certs**: issuer certificates
- **issuer/crl**: revocation lists of issuer certificates

Copy the **X509UserIdentity_PKI** certificates for testing with the UACTT to the following stores:

- **trustedUser/certs**: trusted user certificates
- **trustedUser/crl**: revocation lists of trusted user certificates
- **issuerUser/certs**: user issuer certificates
- **issuerUser/crl**: revocation lists of user issuer certificates

## UACTT Testing

Download and install the [OPC UA Compliance Test Tool](https://opcfoundation.org/developer-tools/certification-test-tools/opc-ua-compliance-test-tool-uactt/).

Note: Access to the UACTT is granted to OPC Foundation Corporate Members.

### UACTT sample configuration

A sample configuration for the UACTT Version [1.04.9.398](https://opcfoundation.org/developer-tools/certification-test-tools/opc-ua-compliance-test-tool-uactt/) can be found in [UAReferenceServer.ctt.xml](./UAReferenceServer.ctt.xml). Originally the reference server was certified only against the **Standard UA Server** profile, the **Method Server Facet** and the **DataAccess Server Facet**, in addition to all security related profiles. During release testing all Conformance Units should be enabled / checked.

### Enabling Alarms & Conditions

The address space for *Alarms* contains a *Start* method which needs to be called to produce alarms for CTT testing. The method is called from a connected client.
The **ConsoleReferenceServer** has also a command line option `-ctt` which starts the Alarms when the server is started. The following Alarm instances are available for monitoring:
- `AlarmConditionType`
- `DiscrepancyAlarmType`
- `LimitAlarmType`
- `ExclusiveLimitAlarmType`
- `ExclusiveDeviationAlarmType`
- `ExclusiveRateOfChangeAlarmType`
- `NonExclusiveLimitAlarmType`
- `NonExclusiveDeviationAlarmType`
- `NonExclusiveRateOfChangeAlarmType`
- `DiscreteAlarmType`
- `SystemOffNormalAlarmType`
- `ExclusiveLevelAlarmType`
- `NonExclusiveLevelAlarmType`
- `OffNormalAlarmType`

### Known missing Tests and Issues

Depending on the setup in the provided project configuration, unsupported profiles should be skipped. At the time of writing (1.4.368) the following tests, profiles or facets are not yet covered or not configured due to issues:

- no support for events, historian and only a few basic Alarms & Conditions.
- Decimal type causes crash of CTT (needs investigation)
- no Image / Enumeration scalar test cases
- Arrays may not include Variant (needs investigation)
- no ArrayItemType implemented
- multiple hierarchical references test node missing
- deprecated security profiles support for SHA1/1k RSA keys implemented not according to certification. SHA1/1k keys can only be turned on/off for all profiles, not just for the deprecated profiles.
- Monitored Items with array are failing a few test cases.

It is recommended to run the server as retail build with disabled logging, to avoid side effects due to timing artifacts when log entries are written to a disk drive.

### Running the CTT against a Docker container

Please refer to the [Docker container of the Reference Server](docs/DockerReferenceServer.md) documentation page. Once setup to map the certificate store and the configuration to a local folder, follow the instructions above to copy the certificates to the PKI and get started.

#### Finding the Address Space Configuration Code

- Project: Reference Server
- File: ReferenceNodeManager.cs
- Method: CreateAddressSpace

#### Finding the UA Services

- Project: Opc.Ua.Server
- File: StandardServer.cs