🎯 Features and goals

• High-level and easy to use classes similar to the Python opcua/asyncua API:
  • opcua::Server
  • opcua::Client
  • opcua::Node
• Free functions in services namespace as an alternative to the opcua::Node class
• Safe wrapper classes for open62541 UA_* types to prevent memory leaks
• Native open62541 objects can be accessed using the handle() method of the wrapping classes
• Extensible type conversion system to convert arbitrary types to/from native UA_* types
• Asynchronous model similar to (Boost) Asio
• Cross-platform (tested on Windows, Linux and macOS)
• Compatible with all stable open62541 versions ≥ v1.0
• Easy installation and integration with CMake
• Use modern C++ (C++ 17) and best practices
• Less hurdle to get started with OPC UA

The latest stable open62541 release is integrated as a submodule. Depending on the value of the CMake flag UAPP_INTERNAL_OPEN62541, the submodule or an external open62541 installation is used. All open62541 releases since v1.0 are supported and tested in a CI pipeline with debug/release builds and as static/dynamic library.

The project is currently in beta stage but already used in production. Version v1.0.0 is planned for 2024. No major breaking changes are expected.

📝 Examples

Explore all examples in the examples/ directory.

Server

#include <open62541pp/open62541pp.hpp>

int main() {
    opcua::Server server;

    // Add a variable node to the Objects node
    opcua::Node parentNode(server, opcua::ObjectId::ObjectsFolder);
    opcua::Node myIntegerNode = parentNode.addVariable({1, 1000}, "TheAnswer");
    // Write value attribute
    myIntegerNode.writeValueScalar(42);

    server.run();
}

Client

#include <iostream>

#include <open62541pp/open62541pp.hpp>

int main() {
    opcua::Client client;
    client.connect("opc.tcp://localhost:4840");

    opcua::Node node(client, opcua::VariableId::Server_ServerStatus_CurrentTime);
    const auto dt = node.readValueScalar<opcua::DateTime>();

    std::cout << "Server date (UTC): " << dt.format("%Y-%m-%d %H:%M:%S") << std::endl;
}

⇆ Type conversion

Type conversion from and to native UA_* types are handled by the opcua::TypeConverter struct. Have a look at the typeconversion example.

Compile-time checks are used where possible:

opcua::Variant var;

// ✅ will compile
int number = 5;
var.assign(&number);

// ❌ won't compile, because std::string can't be assigned without copy (conversion needed)
std::string str{"test"};
var.assign(&str);

// ✅ will compile
var.assign(str);

You can add template specializations to add conversions for arbitrary types:

namespace opcua {

template <>
struct TypeConverter<std::byte> {
    using ValueType = std::byte;
    using NativeType = UA_Byte;

    static void fromNative(const NativeType& src, ValueType& dst) { /* ... */ }
    static void toNative(const ValueType& src, NativeType& dst) { /* ... */ }
};

}  // namespace opcua

Type map of built-in types

Type	Type open62541	Typedef	Wrapper	Conversions
Boolean	UA_Boolean	bool
SByte	UA_SByte	int8_t
Byte	UA_Byte	uint8_t
Int16	UA_Int16	int16_t
UInt16	UA_UInt16	uint16_t
Int32	UA_Int32	int32_t
UInt32	UA_UInt32	uint32_t
Int64	UA_Int64	int64_t
UInt64	UA_UInt64	uint64_t
Float	UA_Float	float
Double	UA_Double	double
String	UA_String		opcua::String	std::string, std::string_view, const char*, char[N]
DateTime	UA_DateTime	int64_t	opcua::DateTime	std::chrono::time_point
Guid	UA_Guid		opcua::Guid
ByteString	UA_ByteString	UA_String	opcua::ByteString
XmlElement	UA_XmlElement	UA_String	opcua::XmlElement
NodeId	UA_NodeId		opcua::NodeId
ExpandedNodeId	UA_ExpandedNodeId		opcua::ExpandedNodeId
StatusCode	UA_StatusCode	uint32_t	opcua::StatusCode
QualifiedName	UA_QualifiedName		opcua::QualifiedName
LocalizedText	UA_LocalizedText		opcua::LocalizedText
ExtensionObject	UA_ExtensionObject		opcua::ExtensionObject
DataValue	UA_DataValue		opcua::DataValue
Variant	UA_Variant		opcua::Variant
DiagnosticInfo	UA_DiagnosticInfo		opcua::DiagnosticInfo

🚀 Getting started

The library can be built, integrated and installed using CMake.

Please check out the open62541 build options here: https://www.open62541.org/doc/1.3/building.html#build-options

Open62541pp provides additional build options:

• UAPP_INTERNAL_OPEN62541: Use internal open62541 library if ON or search for installed open62541 library if OFF
• UAPP_BUILD_DOCUMENTATION: Build documentation
• UAPP_BUILD_EXAMPLES: Build examples for examples directory
• UAPP_BUILD_TESTS: Build unit tests
• UAPP_ENABLE_CLANG_TIDY: Enable static code analysis with Clang-Tidy
• UAPP_ENABLE_INCLUDE_WHAT_YOU_USE: Enable static code analysis with Include What You Use
• UAPP_ENABLE_COVERAGE: Enable coverage analysis
• UAPP_ENABLE_SANITIZER_ADDRESS/LEAK/MEMORY/THREAD/UNDEFINED_BEHAVIOUR: Enable sanitizers

Integrate as an embedded (in-source) dependency

Add it to your project as a Git submodule (git submodule add https://github.com/open62541pp/open62541pp.git) and link it with CMake:

add_subdirectory(extern/open62541pp)  # the submodule directory
target_link_libraries(myexecutable PRIVATE open62541pp::open62541pp)

Integrate as a pre-compiled library

If you build and install this package to your system, a open62541ppConfig.cmake file will be generated and installed to your system. The installed library can be found and linked within CMake:

find_package(open62541pp CONFIG REQUIRED)
target_link_libraries(myexecutable PRIVATE open62541pp::open62541pp)

Integrate via package managers

The library is available through the following package managers:

• vcpkg: Please refer to the vcpkg documentation how to use it within your project. You can easily use vcpkg to build and install open62541pp:

  vcpkg install open62541pp
  

Build and install

# clone repository
git clone --recursive https://github.com/open62541pp/open62541pp.git
cd open62541pp

# build
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DUAPP_BUILD_EXAMPLES=ON -DUAPP_BUILD_TESTS=ON ..
cmake --build .                   # single-configuration generator like Make or Ninja
cmake --build . --config Release  # multi-configuration generator like Visual Studio, Xcode

# run tests
ctest --output-on-failure

# install to system
cmake --install .

Dependencies

• open62541 as integrated submodule or external dependency
• doctest for tests as integrated submodule

🤝 Contribute

Contributions and feature requests are very welcome. Please have a look at the contribution guidelines.