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/****************************************************************************
**
** Copyright (C) 2015 basysKom GmbH, info@basyskom.com
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\module QtOpcUa
\title Qt OPC UA C++ Classes
\ingroup modules
\qtvariable opcua
\since 5.7
\brief List of C++ classes that provide the Qt OPC UA functionality.
To link against the module, e.g. when writing a new plugin, add this line to your \l qmake \c .pro file:
\code
QT += opcua
\endcode
*/
/*!
\page qtopcua-index.html
\since 5.7
\title Qt OPC UA
\brief Implements OPC UA connectivity through a Qt API.
The Qt \l{Qt OPC UA#A short introduction to OPC UA}{OPC UA} module
implements a Qt API to interact with OPC UA on top an external
OPC UA stack.
The stacks are connected via plugins and can be selected/switched at
runtime.
Currently, only the LGPL v3 implementation FreeOPCUA is provided.
Other SDKs can be wrapped in additional plugins.
An HMI focused subset of functionality is implemented in
QOpcUaClient, which can be used to visualize data present on an OPC UA
server.
\section1 A short introduction to OPC UA
OPC UA is a protocol for data modelling and secure exchange of data in
industrial applications.
The protocol offers built-in transport security based on certificates and
established cryptographic algorithms.
The data modelling system is object oriented and offers support for
pre-made models which can be extended to fit special needs.
\section1 Implemented features from the OPC UA protocol
Not all features offered by the plugins can be used with all
backends. The following table shows the current status of implementation.
\table
\header
\li Feature
\li FreeOPCUA
\li Others to come...
\row
\li Reading and writing of values as array/scalar
\li X
\li ?
\row
\li Reading of value ranges
\li
\li ?
\row
\li Reading of engineering units
\li
\li ?
\row
\li Browsing and reading attributes of nodes
\li X
\li ?
\row
\li Secure connection
\li
\li ?
\row
\li User/password auth
\li X
\li ?
\row
\li Data change subscription
\li Unstable implementation in FreeOPCUA
\li ?
\row
\li Event subscription
\li Callback is not called inside FreeOPCUA, so no signal is emitted
\li ?
\row
\li Method calls
\li Low performance
\li ?
\row
\li Historical access
\li
\li ?
\endtable
Asynchronous operations, reading and writing of multiple nodes using one
method call, filters for subscriptions, aggregates and write access for
historical data are not implemented yet.
\section1 Data types
A subset of OPC UA data types are currently supported in QOpcUaClient, most
of them are available with all backends. When writing data to the server,
the type of the value must be specified using the QOpcUaType enum.
\table
\header
\li Data type
\li FreeOPCUA
\li Others to come...
\li Mapping
\row
\li Int8/16/32
\li X
\li
\li Directly used
\row
\li UInt8/16/32
\li X
\li
\li Directly used
\row
\li Double
\li X
\li
\li Directly used
\row
\li Float
\li X
\li
\li Directly used
\row
\li Byte String
\li X
\li
\li QByteArray
\row
\li String
\li X
\li
\li QString
\row
\li Date Time
\li X
\li
\li QDateTime
\row
\li Localized Text
\li X
\li
\li QString
\row
\li Node ID
\li X
\li
\li QString
\row
\li XML Element
\li Not available in FreeOPCUA
\li
\li QByteArray
\endtable
\section1 Classes and ownership
Two important classes are exposed to the user: QOpcUaClient and QOpcUaNode.
Objects of the type QOpcUaNode are owned by the user and must be deleted when they are no longer needed.
\section1 Related Information
\list
\li \l{Qt OPC UA C++ Classes}{C++ Classes}
\li \l{Qt OPC UA Examples}{Examples}
\li \l{https://opcfoundation.org/about/opc-technologies/opc-ua/}{OPC UA at the OPC foundation}
\endlist
*/
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