OPC UA 是用于工业应用程序数据建模和数据交换的协议。
OPC UA 服务器提供对由参考连接节点网格，组织数据的访问。使用不同引用类型和包含元数据的节点，使客户端能够在无需提前知道其结构的情况下导航和解释数据。
Each node has a unique identifier and attributes that can be read and written. Among others, there are 变量 nodes that store values and callable 方法 nodes with attached nodes describing parameters and return values. Notifications in case of events and monitoring of Variable nodes for value changes are offered too.
Complex objects can be created by combining nodes using references. Inheritance is also possible. OPC UA offers support for pre-made models that can be extended to fit special needs.
OPC UA is the platform-independent successor of OPC Classic intended for usage on all levels, from embedded sensors up to manufacturing execution and enterprise resource planning systems. It has a service-oriented architecture based on standardized messages for service requests and responses. There are different ways for these messages to be encoded and transported over the network. The most common way is binary encoding over TCP.
The following table summarizes the features of OPC UA that are supported by Qt OPC UA.
| 特征 |
|---|
| 读取 |
| 批量读取 |
| HistoryRead (Raw) |
| 写入 |
| 批量写入 |
| 多维数组 |
| 浏览 |
| 数据改变订阅 |
| 事件订阅 |
| 修改订阅/监视项 |
| 方法调用 |
| 浏览路径分辨率 |
| GetEndpoints |
| FindServers |
| NodeManagement |
| RegisterNodes |
| UnregisterNodes |
A subset of the OPC UA data types is currently supported in Qt OPC UA.
Two important classes are exposed to the user: QOpcUaClient and QOpcUaNode .
Objects of both classes are owned by the user and must be deleted when they are no longer needed.
The following table summarizes the logging categories that are used by Qt OPC UA.
| 日志类别 | 描述 |
|---|---|
| qt.opcua | Plugin independent messages generated by QOpcUaProvider and QOpcUaClient |
| qt.opcua.plugins.open62541 | Messages generated by the open62541 plugin |
The open62541 sdk logging categories depend on the log level for open62541, which is configured at compile time. The default is 300, which enables: info, warning, error and critical. To obtain less or more verbose output, the open62541 sdk needs to be rebuilt with a different configuration.
The following table shows the logging categories used by open62541:
| Open62541 Logging Category | 描述 |
|---|---|
| qt.opcua.plugins.open62541.sdk.network | Messages generated by the open62541 network |
| qt.opcua.plugins.open62541.sdk.securechannel | Messages generated by the open62541 channel |
| qt.opcua.plugins.open62541.sdk.session | Messages generated by the open62541 session |
| qt.opcua.plugins.open62541.sdk.server | Messages generated by open62541 server components |
| qt.opcua.plugins.open62541.sdk.client | Messages generated by the open62541 client |
| qt.opcua.plugins.open62541.sdk.userland | Messages generated by the open62541 userland |
| qt.opcua.plugins.open62541.sdk.securitypolicy | Messages generated by the open62541 security policies |
The Qt OPC UA module is available under commercial licenses from Qt 公司 。此外，它在自由软件许可下也是可用的。这些自由软件许可是 GNU LGPL (次一般公共许可) 第 3 版 ，或 GNU GPL (一般公共许可) 第 2 版 。见 Qt 许可 进一步了解细节。
Qt OPC UA in Qt 6.7.2 may contain third party modules under following permissive licenses:
| Mozilla Public License 2.0 and Creative Commons Zero v1.0 Universal and Creative Commons Attribution Share Alike 4.0 International and BSD 3-Clause "New" or "Revised" License and Apache License 2.0 and MIT License |
Linking to external libraries involves licenses from the backend providers.
The Open62541 plugin is available under the same licenses as Qt OPC UA. The Open62541 library itself is licensed under Mozilla 公共许可第 2.0 版 .
The security support is provided by the OpenSSL plugins of the open62541 library. If the open62541 plugin is built with security support and OpenSSL is not available on the target system, the open62541 plugin will fail to load.
