C++ OPC UA SDK from One-Way Automation - public redistributables
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README.md

README.md

1WaOpcUaSdk

C++ OPC UA SDK from One-Way Automation - public redistributables.

Summary

This SDK is intended to extremely simplify creation of OPC UA Client and Server Applications in modern C++. The plan is to implement OPC UA communication stack and provide high level classes to asynchronously send, receive and handle OPC UA requests and responses, and have built-in support for standard OPC UA Server or Client features (example for server side - managing of endpoints, namespaces, sessions, interface for plug-ins to collect data from external data sources, etc). Primary target and narrow specialization of this SDK are high performance OPC UA applications running in PC or cloud environment. It is expected that it will be resource unpretentious and run in lower end hardware such as Raspberry PI though, but narrow specialization will be to satisfy requirements for enterprise scale applications.

Includes header files and pre-built binaries for Visual Studio 2017.

Binaries for other targets can be created up on request - please feel free to create an issue!

Key differentiators

The key differentiators of this SDK from other existing in the market C++ SDKs will be:

  • Written in modern C++ (11 or higher);
  • Leverages existing open source libraries (boost for asynchronous communication, Botan for cryptography, ODB for Object-Relational Mapping) to shorten time to market.
  • Cloud ready - microservice-style applications can be created by using of this SDK, which then should be able to be deployed and run on such environments as Azure Service Fabric and Cloud Foundry.
  • Foundation for IoT connectivity applications to deliver data and object model from various factory level data sources (OPC UA Servers) to the Cloud and then provide access to that data and model from the Internet via OPC UA interface.
  • Does not depend on OPC Foundation's ANSI C Stack, has its own stack implementation.
  • Asynchronous interface (which can also be used as synchronous). For client side, the interface uses std::future to return results and optionally possible to handle result via callback defined as std::function. Callbacks are made from dedicated for that threads, so they do not affect other threads such as io service threads.This simplifies using the SDK for GUI applications for example.
  • Easy extensibility to add new encoding or transport protocols. Supported encoding/transport combinations could be:
    • binary / opc.tcp
    • binary / opc.amqp
    • json / opc.amqp
    • json / https
  • Two way communication - once an OPC UA session is established, both sides of the session can send/receive requests and responses (so it is different from "reversible" connection using ReverseHelloMessage, which still one-way mode). Use cases where this feature can be beneficial:
    • Can be used as true Machine To Machine communication media;
    • Can be used to build cloud relay without opening single port in the firewall too.
    • Can simplify communication between redundancy set members.
  • For Client side, automatic re-connection with automatic creation of subscriptions and adding monitored items.
  • Persistent storage to save/load configuration parameters and some current state parameters in both client side and server side:
    • Client:
      • Namespace array to keep NodeIds static even if server side namespace array is changed;
      • Subscriptions and monitored items. No server side handles are exposed - instead static client handles defined by the application are used, which simplifies mapping of received data changes to the right recipient after re-connections for example.
      • Maintains cache of server's address space, so it can be browsed in offline mode when target server is not available;
    • Server:
      • Address space stored in data base. This removes restrictions for the number of nodes in address space by RAM size. As a result, it makes easy to create for example horizontally scale-able OPC UA Aggregating Server, which can combine address space of hundreds and thousands of factory level OPC UA Servers into common address space in the Cloud, accessible via single endpoint. The same endpoint can also be used to access historical and real time data, with high throughput (millions of data changes per second, utilizing fleet of instances if required).
      • Sampled data values queue stored in database - storing it allows implementation of coming new feature in OPC UA "durable subscriptions" - where even long disconnections do not cause data loss.
      • Sessions and Monitored Items - makes easy to implement "transparent redundancy", where after re-connecting to the other instance, the client does not need to create subscriptions and monitored items again. This is also directly related to support of horizontal scale-ability.

Current status of the project

It is in "incubation" stage. Source code is stored in private repository. Basic proof of concept coding is done for the client side.

Implemented features for client side:

  • Establishing TCP connection and initial handshake (OPC UA Hello, Acknowledge and Error messages);
  • Implemented OPC UA Services:
    • OpenSecureChannel
    • FindServers
    • GetEndpoints
    • CreateSession
    • ActivateSession
    • Read
    • Browse
    • BrowseNext
    • CreateSubscription
    • DeleteSubscriptions
    • CreateMonitoredItems (for Data Changes only, no Alarms/Events)
    • DeleteMonitoredItems;
    • Publish
    • CloseSecureChannel
  • Communication in secured mode and infrastructure to support it:
    • Generating self-signed root certificate and application instance certificate signed by it;
    • Creation of secure channel in secured mode (sign and encryption).
  • OPC Binary encoding: implemented for most data types, required to send requests and receive responses for functionality listed above.

Road-map

Version 1.0

  • Client side features only.
  • Polish features listed in section "Current status of the project"
  • Add support for services required to have "minimum viable product":
    • TranslateBrowsePathsToNodeIds
    • Write
    • ModifySubscription;
    • ModifyMonitoredItems;
  • Create 64 bit installers for Windows and Linux

Next versions

TBD.

License and Copyright

Copyright 2018, One-Way Aautomation Inc.

Versions prior 1.0 can be distributed and used under MIT license terms (https://opensource.org/licenses/MIT)

For versions starting from 1.0 licensing terms might change. Various options are under consideration, open source and commercial, such as:

  • Dual License:
    • GPL
    • Commercial
  • MIT license (unrestricted).
  • Different licensing for different editions:
    • Community - free
    • Professional - Commercial

Final decision will depend on how the project is perceived by OPC UA community.

For open source projects, as well as for personal usage and educational purposes binary redistributables will be free.

How to use

For instructions how to use it please visit home page for the sample OPC UA Test Client project: