Async OPC-UA

This is an OPC-UA server / client API implementation for Rust.

OPC-UA is an industry standard for information modeling and communication. It is used for control systems, IoT, etc.

The OPC-UA standard is very large and complex, and implementations are often flawed. The strictness of Rust makes it a good choice for implementing OPC-UA, and the performance characteristics are useful when creating OPC-UA tooling that will run in constrained environments.

Read the compatibility page for how the implementation conforms with the OPC UA spec.

Read the change log for changes per version as well as aspirational / upcoming work.

This is a fork

This is a fork of opcua with a broader goal of a generic OPC-UA implementation and a number of different design decisions. See fork.md for details on this decision and the differences between this library and the original.

MSRV Policy

We target the latest stable rust compiler and make no promises of support for older rust versions. We have use for several recent and upcoming rust features so this is unlikely to change.

License

The code is licenced under MPL-2.0. Like all open source code, you use this code at your own risk.

Documentation

Tutorials for using the server and client are available in the async-opcua github repo:

• Client Tutorial
• Server Tutorial
• General documentation
• Library design

There are also generated API docs on crates.io.

Features

• all, enables the server and client features.
• server, includes the server SDK.
• base-server, includes the server SDK, but without the core address space. Most users should use the server feature.
• client, includes the client SDK.
• json, adds support for OPC-UA JSON to generated types.
• generated-address-space, adds the core OPC-UA namespace. This is usually required for compliant OPC-UA servers.
• discovery-server-registration, allows the server to register itself with a local discovery server, by pulling in a client.
• xml, adds support for loading generated types from XML, and for loading NodeSet2.xml files.

By default, no features are enabled, so only core types and functionality is pulled in. You will typically want to enable either the client or server features.

Crates

Note that this library is split into multiple different crates. OPC-UA is a complex standard, and implementations typically involve a great deal of generated code. In order to allow good isolation of different components, and to speed up compile times, the async-opcua library is split into several crates.

• async-opcua, the general crate that most users will use as the entry point. Contains a few utilities, but mostly just re-exports the other crates. I.e. async-opcua-types is re-exported under opcua::types.
• async-opcua-client contains a fully featured OPC-UA client.
• async-opcua-server contains a flexible SDK for building OPC-UA servers.
• async-opcua-core contains common primitives and tools for implementing the OPC-UA communication protocol.
• async-opcua-core-namespace contains generated code for the entire OPC-UA core namespace.
• async-opcua-crypto contains common cryptographic tooling for the OPC-UA protocol using libraries from Rust Crypto.
• async-opcua-macros contains a few macros used to create custom extensions to the OPC-UA standard.
• async-opcua-nodes contains an in-memory representation of OPC-UA nodes, used by the server.
• async-opcua-types contains the framework used by serialization and deserialization to OPC-UA Binary and JSON, and deserialization from OPC-UA XML. It also contains generated code defining types from the OPC-UA standard, and manual implementations of a number of core types.
• async-opcua-xml contains an implementation of XML decoding for certain XML schemas relevant to OPC-UA.

Samples

The async-opcua github repo contains a number of samples that may be used as reference when writing your own clients and servers.

1. simple-server - an OPC-UA server that adds 4 variables v1, v2, v3 and v4 and updates them from a timer via push and pull mechanisms.
2. simple-client - an OPC-UA client that connects to a server and subscribes to the values of v1, v2, v3 and v4.
3. discovery-client - an OPC-UA client that connects to a discovery server and lists the servers registered on it.
4. chess-server - an OPC-UA server that connects to a chess engine as its back end and updates variables representing the state of the game.
5. demo-server - an OPC-UA server that is more complex than the simple server and can be used for compliance testing.
6. mqtt-client - an OPC-UA client that subscribes to some values and publishes them to an MQTT broker.
7. event-client - an OPC-UA client that will connect to a server and subscribe to alarms / events.
8. custom-codegen - an OPC-UA server that implements an OPC-UA companion standard generated using async-opcua-codegen.