The Qt WebSockets module provides C ++ and QML interfaces, which enables Qt applications to act as servers for processing WebSocket requests, or as clients for receiving data from servers, or both.
To include the definition of the module class, use the following instructions:
To import QML types into your application, please use the. Qml file:
To link the module, add the following line to qmake. Professional documents:
Qt WebSockets enables you to build applications that support WebSockets. It provides the implementation of WebSocket protocol, which is provided by IETF (Internet Engineering Task Force) and is a better alternative to using the existing Web infrastructure for two-way communication.
Historically, Web applications that need two-way communication or push notifications must use available HTTP-based solutions. These solutions use different technologies, such as polling, long polling and streaming, to overcome the limitations of HTTP protocols, which are not designed for this use case. This leads to high network delay, unnecessary data exchange and outdated or old data. IETF WebSocket products help overcome these problems to a great extent.
As shown in the figure, the solution based on WebSocket consists of client and server. The most popular web browsers (such as Google Chrome, Internet Explorer, Safari, etc. ) provides local client support for WebSocket. The server-side support of WebSocket makes it a complete solution, thus realizing two-way communication. Any browser that supports local WebSocket should allow you to run simple client applications based on HTML and JavaScript using the HTML5 WebSocket API.
WebSocket WebSocket connection starts with the initial HTTP compatible handshake, which ensures backward compatibility and enables WebSocket connection * * * to enjoy the default HTTP(80) and HTTPS(443) ports. After the handshake is successful, the connection will be opened for data exchange until one of the two entities ends the connection.
The Web socket protocol of WebSocket uses ws: and wss :URL schemes to represent insecure and secure WebSocket requests respectively. During the initial handshake, if a proxy server is detected, the protocol will try to establish a tunnel by sending a statement to the HTTP CONNECT proxy. Although it has been proved that TLS (transport layer security) can work better in secure connections, tunnel method is used to handle proxies regardless of the request type.
WebSocket is best suited for the following situations:
Some sample applications that we try to achieve these goals through traditional methods, such as instant messaging, online games, online stock trading, etc.
Qt WebSockets module provides API to develop server and client applications based on WebSocket. Examples of these APIs that can be used are server applications that provide stock data, and client applications that register push notifications when the prices of some stocks change.
This module provides C ++ and QML versions of API, so you can choose an alternative method that suits your needs.
Client applications usually rely on external services to obtain data. Most of these service providers do not support WebSocket yet, so it is necessary to develop WebSocket-aware server applications to bridge this gap. You can run servers on enterprise WebSocket gateway services, such as cloud services, thus avoiding the trouble of maintaining the necessary infrastructure required to host such services.
Most cloud services provide a platform-as-a-service (PaaS) backend, where instances of server applications can be deployed and run on the cloud. Client applications can use WebSocket URL to connect to a running server and receive data.