網絡和連接

Qt provides classes for both high-level and low-level network communication, classes for web integration, and classes for inter-process communication (IPC).

對於高級網絡流量， Qt Network 提供僅展示高級類和函數，覆蓋所用操作的抽象層。Qt Network 還可以處理像 TCP 和 UDP 的低級協議。類 QTcpSocket and QUdpSocket enable the developer to send and receive messages using the TCP or UDP protocol. Name resolution is done with QHostInfo . QHostInfo 被調用，先於創建網絡連接采用 QTcpSocket or QUdpSocket . Filtering and redistributing network traffic via proxies can be handled by the QNetworkProxy 類。

Qt 提供 connectivity options to connect systems or applications using modules like Qt Bluetooth , which provides connectivity between Bluetooth enabled devices. Qt Serial Bus provides classes and functions to access the various industrial serial buses and protocols, and Qt NFC provides connectivity between NFC enabled devices. Also, Qt Serial Port provides the basic functionality, including configuring, I/O operations, and getting and setting the control signals of the RS-232 pinouts.

Qt offers functionalities for Inter-Process Communication. The class QProcess 被用於啓動外部程序。 Qt D-Bus provides support for D-Bus, an inter-process communication and remote procedure calling mechanism. It communicates via a central server application called a bus. However, it is also possible to let applications communicate directly with each other. QSharedMemory provides access to a shared memory segment by multiple threads and processes. However, a single process can exclusively lock that shared memory.

網絡通信

Qt 支持廣泛網絡通信，重點是 HTTP、TCP 及 UDP。

在 HTTP 級彆， Qt Network 模塊提供網絡訪問 API，主要包括 QNetworkRequest , QNetworkAccessManager ，和 QNetworkReply 。 QNetworkRequest 類似於 HTTP 請求，其被傳遞給 QNetworkAccessManager 以發送綫上請求；此類返迴 QNetworkReply , which enables parsing the HTTP reply. The network access API internally uses the socket classes mentioned below (for TCP and SSL).

QTcpSocket , QUdpSocket ，和 QSslSocket should be used for communication at the socket level. These classes offer a synchronous API through the waitFor* methods as well as an asynchronous API; if possible (that is if the event loop is running), the asynchronous API should always be preferred. Qt also offers QTcpServer to enable the server-side part of a TCP communication.

為憑藉 SSL 進行安全通信，Qt Network 提供廣泛的類，除瞭中心 QSslSocket 。例如， QSslCertificate , QSslConfiguration ，和 QSslError .

Qt also offers HTTP support in QML by either using HTTP explicitly via XmlHttpRequest, or by transparently using HTTP URLs in Image sources for example.

相關話題：

用 Qt 進行網絡編程
SSL (安全套接字層) 類
資源加載和網絡透明度 - 在 QML 中的網絡和 URL 透明度
Qt Network Authorization - set of APIs that enable Qt applications to obtain limited access to online accounts and HTTP services without exposing users' passwords.
Qt Remote Objects - an inter-process communication (IPC) module that enables information exchange between processes or computers.
Qt MQTT - machine-to-machine (M2M) protocol that uses the publish-and-subscribe paradigm to provide a channel with minimal communication overhead.
Qt OPC UA - server that offers access to data that is organized in a mesh of nodes connected by references. The use of different reference types and nodes containing metadata enables a client to navigate and interpret the data without knowing their structure in advance.
Qt WebSockets - web-based protocol designed to enable a two-way interactive communication session between a client application and a remote host. It enables the two entities to send data back and forth if the initial handshake succeeds.
Qt WebChannel - enables peer-to-peer communication between a server (QML/C++ application) and a client (HTML/JavaScript or QML application). It is supported out of the box by Qt WebEngine . In addition, it can work on all browsers that support WebSockets, enabling Qt WebChannel clients to run in any JavaScript environment (including QML). This requires implementing a custom transport based on Qt WebSockets.
Qt Protobuf - a generator that can be used to generate Qt-based classes from .proto 文件。
Qt GRPC - allows you to define data and messages in proto files and then use the code generators, which generate code allowing accessors for fields and gRPC services in the Qt framework.

Connectivity

Qt supports a range of connectivity options, with a focus on Qt Serial Bus , Qt Serial Port , Qt Bluetooth and Qt NFC .

Qt Serial Bus - provides classes and functions to access the various industrial serial buses and protocols, such as CAN, ModBus, and others.
Qt Serial Port - provides the basic functionality, which includes configuring, I/O operations, getting and setting the control signals of the RS-232 pinouts.
Qt Bluetooth - provides classes and functions to use Bluetooth devices, which includes scanning for devices, gathering information, and exchanging data between them. Qt Bluetooth supports both Classic and Low Energy Bluetooth technologies.
Qt NFC - provides classes and functions to establish connectivity between NFC enabled devices. NFC is a short-range (less than 20 centimeters) wireless technology with a maximum transfer rate of 424 Kbps. NFC is ideal for transferring small packets of data when two devices are placed together.

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