opcuapp

A self-contained OPC UA Binary / WebSocket stack: secure-channel + wire codec, shared client/server session and subscription runtime, and a WebSocket (JSON-over-WS) transport. Extracted from the Telecontrol SCADA monorepo (common/opcua) with zero dependency on the SCADA core repo.

Layout

opcua/
  base/        vendored generic infrastructure (Awaitable, AnyExecutor, time, ...)
  services/    OPC UA service callback and request helper types
  monitored/   OPC UA MonitoredItem subscription boundary
  metrics/     vendored trace-id helper
  net/         vendored executor adapter
  *.h / *.cpp  the OPC UA stack itself (sessions, runtime, endpoints) -> namespace opcua
  transport/   transport backends:
    binary/      OPC UA Binary wire codec, secure channel, crypto
    websocket/   OPC UA over WebSocket (Boost.Beast + JSON codec)
  test/        test fixtures

Namespacing

So that a consumer can include both this library and the SCADA core library in one translation unit without ODR clashes, OPC UA protocol symbols live in namespace opcua and are therefore distinct from core's:

• OPC UA protocol/service types: opcua::X
• MonitoredItem subscription boundary: opcua::X
• generic base classes: base::X -> opcua::base::X
• async infrastructure aliases: global Awaitable / AnyExecutor -> opcua::Awaitable / opcua::AnyExecutor
• low-level, domain-free utilities (UtfConvert, Format, debug_util's operator<</ToString, StructWriter, SharedValue, ...) -> opcua::...

A whole-file wrap (rather than nesting only the obvious namespaces) is required because the codebase relies on a global ToString / operator<< overload set that type headers extend; wrapping only part of it would shadow the rest for namespace-nested callers. namespace std / boost / transport blocks (hash specializations, Boost.Log ADL helpers, external forward declarations) are excluded from the wrap and stay at their original scope. boost_log.h is left global (its macros reference ::-qualified names and it is only included by .cpp internals, never a public header).

The native stack already lives in namespace opcua, so it reaches the MonitoredItem subscription boundary plus opcua::base / opcua::Awaitable symbols via enclosing-namespace lookup with no per-call qualification.

Building (standalone)

Requires Boost (asio, json, log, beast, locale), OpenSSL, and the transport library, which the net product provides. net must be checked out beside this repository as ../net; the resolver in build-support/ finds it there (and in the SCADA monorepo, where it lives at third_party/net).

cmake --preset ninja
cmake --build --preset release      # or: debug, relwithdebinfo
ctest --preset test-release         # or: test-debug

Every product in the SCADA tree carries this same preset set (ADR 0011). Set VCPKG_ROOT in the environment; anything else machine-specific goes in .scada-local.cmake beside build-support/. Output lands in build/ninja/bin/<config>/.

The ninja preset turns OPCUAPP_BUILD_TESTS on. The option itself defaults to OFF so a consumer does not pay for the 48 unit-test files, but a build of opcuapp itself runs them.

If net is somewhere else, name it: -DSCADA_PRODUCT_ROOT_NET=/path/to/net (or keep using -DOPCUAPP_TRANSPORT_DIR=/path/to/net, which still works).

Consumers use find_package(opcuapp) (via Findopcuapp.cmake on CMAKE_MODULE_PATH) and link opcuapp::opcuapp. The module filename is lowercase to match the call site; on a case-sensitive filesystem any other spelling fails to resolve.

History

The tree under opcua/ was originally vendored mechanically from the SCADA monorepo (core/common) by one-shot scripts in a tools/ directory. The sources have since diverged from the monorepo (renames, reorganization, new features), so the vendoring scripts were removed; this repo is now the sole home of these sources.

License

MIT — see LICENSE.