Open62541 is an open source OPC UA SDK written in C that can be used to build OPC UA servers and clients. It has a small code size and memory footprint. It has no external dependencies and supports multiple platforms. Open62541 uses continuous integration testing and aims to have no known bugs. It has an active community of contributors working on features like encryption and improving performance.

1. open62541
Open Source OPC UA on
Steroids
Julius Pfrommer (KIT / Fraunhofer IOSB)
julius.pfrommer@kit.edu
julius.pfrommer@iosb.Fraunhofer.de
June 2016
open62541 originated at:

2. open62541 in a Nutshell
• Open Source OPC UA SDK (Stack + Server + Client)
• Written in C99 (builds with GCC / Clang / MSVC)
• Platform independent
• Endianness-agnostic
• No external dependencies of the core library (a few tiny .c
files in the /deps folder, e.g. a random number generator)
• Plugins for OS-dependent features with implementations for
the major platforms (networking, logging, clock, …)
• Distributed as a single open62541.c/.h pair
• License: LGPL + static linking exception. Can be linked
with commercial code, only changes to the library itself
need to be published

3. Goals of open62541
What?
OPC UA is great as a technology. Let’s make it easily
accessible to increase adoption.
How?
• Be the “Apache Server” of machine communication
• Allow tinkering/prototyping with the technology
• Provide a readable and concise implementation
(learn by reading the code along with the standard)
Not: Provide commercial support

4. open62541 is small
• Server binary down to 75kb / Client down to 40kb
• Server runs with 60kb RAM (mostly due to the large
information model loaded by default)
• Most code is generated from XML definitions
• Content of the /src and /include directories:
http://cloc.sourceforge.net v 1.64 T=0.17 s (277.8 files/s, 97617.7 lines/s)
-------------------------------------------------------------------------------
Language files blank comment code
-------------------------------------------------------------------------------
C 25 1201 744 10291
C/C++ Header 22 617 1183 2482
-------------------------------------------------------------------------------
SUM: 47 1818 1927 12773
-------------------------------------------------------------------------------

5. open62541 is fast
• Event-driven / Async server design
• Speed / cache efficiency considered from the start
• 16,000 req/sec measured with Posix sockets on a
single core
• Can be greatly improved by using epoll/kqueue or high-
throughput kernel-level mechanisms, such as DPDK
• 1,000,000 read req/sec without networking (request
decoding, processing, response encoding)
• 10,000 DataChange MonitoredItems with a 50ms
sampling rate  15% CPU load on a single core

6. • Continuous Integration for every commit
• Builds on GCC, MinGW, Clang, MSVC with very conservative
settings (-Wall -Wextra -Werror and more)
• Unit and integration tests (currently ca. 60% coverage)
• Static code analysis: Clang Analyzer, Coverity, Cppcheck
• Runtime sanitizers: Valgrind, Address Sanitizer, Memory
Sanitizer, Undefined Behaviour Sanitizer
• Conformance Testing Tools
• Very comprehensive set of tests
• Provided by the OPC Foundation
• Fuzzing of the network input (afl-fuzzer)
• Zero-known-bugs policy for releases
open62541 is high quality

7. open62541 is community-driven
The people who started everything in 2014 (the 5th is holding the camera)
• Development on Github (no infrequent code-dumps)
• Public Issue Tracker / Mailing List / IRC Channel
• 34 direct contributors to the code so far (statistics from
Github, June 2016)
Picture: OPC UA Workshop / open62541 User Meeting at RWTH Aachen (September 2015)

8. open62541 Roadmap
Currently Supported
• Micro-Embedded Profile
• OPC UA Binary Protocol
• Read/Write/etc.
• Subscriptions/DataChange
MonitoredItems
• Methods
• Runtime changes to the
information model (add/delete
nodes & references)
• Constructor / Destructor for
Object/Variant Instantiation
Mid-term Future
• Encryption
• MonitoredItem Filtering
• Events + Triggering
• Event-driven Client
• Async Services
• Subscriptions Handling in the
Background
Topics that are up for grabs
• User Access Levels
• Finish/Verify lockless multicore
server