Building open62541

open62541 uses CMake to build the library and binaries. The library version is automatically detected using git describe. This command returns a valid version string based on the current tag. If you did not directly clone the sources, but use the tar or zip package from a release, you need to manually specify the version. In that case use e.g. cmake -DOPEN62541_VERSION=v1.0.3.

Building the Examples

Using the GCC compiler, the following calls build the examples on Linux.

cp /path-to/open62541.* . # copy single-file distribution to the local directory
cp /path-to/examples/tutorial_server_variable.c . # copy the example server
gcc -std=c99 -DUA_ARCHITECTURE_POSIX open62541.c tutorial_server_variable.c -o server

Building the Library

Building with CMake on Ubuntu or Debian

sudo apt-get install git build-essential gcc pkg-config cmake python

# enable additional features
sudo apt-get install cmake-curses-gui # for the ccmake graphical interface
sudo apt-get install libmbedtls-dev # for encryption support
sudo apt-get install check # for unit tests
sudo apt-get install python-sphinx graphviz # for documentation generation
sudo apt-get install python-sphinx-rtd-theme # documentation style

cd open62541
mkdir build
cd build
cmake ..

# select additional features
ccmake ..

# build documentation
make doc # html documentation
make doc_pdf # pdf documentation (requires LaTeX)

Building with CMake on Windows

Here we explain the build process for Visual Studio (2013 or newer). To build with MinGW, just replace the compiler selection in the call to CMake.

cd <path-to>\open62541
mkdir build
cd build
<path-to>\cmake.exe .. -G "Visual Studio 14 2015"
:: You can use use cmake-gui for a graphical user-interface to select features
  • Then open buildopen62541.sln in Visual Studio 2015 and build as usual

Building on OS X

brew install cmake
pip install sphinx # for documentation generation
pip install sphinx_rtd_theme # documentation style
brew install graphviz # for graphics in the documentation
brew install check # for unit tests

Follow Ubuntu instructions without the apt-get commands as these are taken care of by the above packages.

Building on OpenBSD

The procedure below works on OpenBSD 5.8 with gcc version 4.8.4, cmake version 3.2.3 and Python version 2.7.10.

  • Install a recent gcc, python and cmake:
pkg_add gcc python cmake
  • Tell the system to actually use the recent gcc (it gets installed as egcc on OpenBSD):
export CC=egcc CXX=eg++
  • Now procede as described for Ubuntu/Debian:
cd open62541
mkdir build
cd build
cmake ..

Build Options

The open62541 project uses CMake to manage the build options, for code generation and to generate build projects for the different systems and IDEs. The tools ccmake or cmake-gui can be used to graphically set the build options.

Most options can be changed manually in ua_config.h (open62541.h for the single-file release) after the code generation. But usually there is no need to adjust them.

Main Build Options

  • RelWithDebInfo -O2 optimization with debug symbols
  • Release -O2 optimization without debug symbols
  • Debug -O0 optimization with debug symbols
  • MinSizeRel -Os optimization without debug symbols

The SDK logs events of the level defined in UA_LOGLEVEL and above only. The logging event levels are as follows:

  • 600: Fatal
  • 500: Error
  • 400: Warning
  • 300: Info
  • 200: Debug
  • 100: Trace

Select build artefacts

By default only the main library shared object (open62541.dll) or static linking archive open62541.a (open62541.lib) is built. Additional artifacts can be specified by the following options:

Compile example servers and clients from examples/*.c.
Compile unit tests. The tests can be executed with make test
Generate a self-signed certificate for the server (openSSL required)

Detailed SDK Features

Enable subscriptions
Enable the use of events for subscriptions. This is a new feature and currently marked as EXPERIMENTAL.
Enable the Method service set
Enable dynamic addition and removal of nodes at runtime
Compile a single-file release into the files open62541.c and open62541.h. Not receommended for installation.
Enable multi-threading support. Work is distributed to a number of worker threads. This is a new feature and currently marked as EXPERIMENTAL.
Nodes in the information model are not edited but copied and replaced. The replacement is done with atomic operations so that the information model is always consistent and can be accessed from an interrupt or parallel thread (depends on the node storage plugin implementation). This feature is a prerequisite for UA_ENABLE_MULTITHREADING.
Measure the coverage of unit tests
Enable Discovery Service (LDS)
Enable Discovery Service with multicast support (LDS-ME)
Enable Discovery Semaphore support


Namespace zero contains the standard-defined nodes. The full namespace zero may not be required for all applications. The selectable options are as follows:

  • MINIMAL: A barebones namespace zero that is compatible with most clients. But this namespace 0 is so small that it does not pass the CTT (Conformance Testing Tools of the OPC Foundation).
  • REDUCED: Small namespace zero that passes the CTT.
  • FULL: Full namespace zero generated from the official XML definitions.

The advanced build option UA_FILE_NS0 can be used to override the XML file used for namespace zero generation.

Some options are marked as advanced. The advanced options need to be toggled to be visible in the cmake GUIs.

Add the type and member names to the UA_DataType structure. Enabled by default.
Compile the human-readable name of the StatusCodes into the binary. Enabled by default.
Use the full NS0 instead of a minimal Namespace 0 nodeset UA_FILE_NS0 is used to specify the file for NS0 generation from namespace0 folder. Default value is Opc.Ua.NodeSet2.xml

Debug Build Options

This group contains build options mainly useful for development of the library itself.

Enable assertions and additional definitions not intended for production builds
Dump every package received by the server as hexdump format

Building a shared library

open62541 is small enough that most users will want to statically link the library into their programs. If a shared library (.dll, .so) is required, this can be enabled in CMake with the BUILD_SHARED_LIBS option. Note that this option modifies the ua_config.h file that is also included in open62541.h for the single-file distribution.

Minimizing the binary size

The size of the generated binary can be reduced considerably by adjusting the build configuration. With open2541, it is possible to configure minimal servers that require less than 100kB of RAM and ROM.

The following options influence the ROM requirements:

First, in CMake, the build type can be set to CMAKE_BUILD_TYPE=MinSizeRel. This sets the compiler flags to minimize the binary size. The build type also strips out debug information. Second, the binary size can be reduced by removing features via the build-flags described above.

Second, setting UA_NAMESPACE_ZERO to MINIMAL reduces the size of the builtin information model. Setting this option can reduce the binary size by half in some cases.

Third, some features might not be needed and can be disabled to reduce the binary footprint. Examples for this are Subscriptions or encrypted communication.

Last, logging messages take up a lot of space in the binary and might not be needed in embedded scenarios. Setting UA_LOGLEVEL to a value above 600 (FATAL) disables all logging. In addition, the feature-flags UA_ENABLE_TYPENAMES and UA_ENABLE_STATUSCODE_DESCRIPTIONS add static information to the binary that is only used for human-readable logging and debugging.

The RAM requirements of a server are mostly due to the following settings:

  • The size of the information model
  • The number of connected clients
  • The configured maximum message size that is preallocated