Ajax technical analysis: What are the supported protocols?

Ajax (Asynchronous JavaScript and XML) technology is a technology used to create dynamic web applications. It realizes asynchronous loading of data by exchanging data with the server in the background, so that the web page has the ability to partially refresh. Users can obtain new content or update existing content without refreshing the entire page. Ajax technology not only improves user experience, but also greatly reduces server load and improves web page performance.

Ajax technology uses a variety of protocols to exchange data. Let’s briefly analyze the common protocols supported by Ajax.

1. HTTP Protocol
   HTTP (Hypertext Transfer Protocol) is an application layer protocol used to transmit hypertext. Ajax sends a request through the HTTP protocol to obtain the data returned by the server. Cross-domain requests can be implemented using the HTTP protocol to obtain data from different servers. Common Ajax request methods include GET and POST, as well as some other methods such as PUT, DELETE, etc.
2. XML Protocol
   XML (eXtensible Markup Language) is a markup language used to describe and transmit data. The earliest version of Ajax used XML as the format for data exchange. Through the XML protocol, the server returns the data to the client in the form of XML, and the client parses the XML through JavaScript to extract the required data. However, because the format of XML is relatively redundant and complex to parse, XML is rarely used as the data exchange format for Ajax.
3. JSON Protocol
   JSON (JavaScript Object Notation) is a lightweight data exchange format, using a completely language-independent text format, with a simple structure and good readability. Ajax usually uses JSON as the data exchange format because JSON is more compact and easier to parse than XML. The server returns the data to the client in JSON format, and the client directly parses the JSON through JavaScript to extract the required data.
4. WebSocket Protocol
   WebSocket is a full-duplex communication protocol based on TCP. It can establish a persistent connection between the client and the server and achieve real-time two-way data transmission. The WebSocket protocol can be used to implement functions such as real-time chat and real-time data updates. Compared with Ajax, it is more efficient and more real-time. Through the WebSocket protocol, the client can send requests to the server, and the server can also actively push data to the client, and the two parties can communicate in real time.
5. WebSocket Handshake Protocol
   Before using the WebSocket protocol, a handshake operation is required to establish a WebSocket connection. The handshake protocol uses the HTTP protocol for communication. The client sends an HTTP request and the server returns an HTTP response. After the handshake is successful, a WebSocket connection is established between the client and the server. The WebSocket handshake protocol makes the WebSocket protocol compatible with existing Web infrastructure.

Summary:
Ajax technology, as a technology for creating dynamic web applications, supports multiple protocols. Among them, the HTTP protocol is essential for sending requests and receiving responses. XML and JSON protocols are used for data exchange, with JSON being more commonly used nowadays. The WebSocket protocol and the WebSocket handshake protocol can be used to achieve real-time two-way communication. Understanding these protocols is very helpful when developing applications that use Ajax technology. At the same time, it should be noted that when using these protocols, corresponding specifications and security requirements need to be observed to ensure the stability and security of the program.

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