What is HTTP?

HTTP refers to Hypertext Transfer Protocol, an application layer protocol used to transmit hypertext data. It is the basis that allows servers and clients of the World Wide Web to communicate.

Definition and Development of HTTP

The HTTP protocol was created in 1989 by British computer scientist Tim Berners-Lee. At the time, he was working at CERN (the European Center for Nuclear Research), where he proposed a new method for sharing hypertext files between different computers. This is the prototype of HTTP.

The earliest HTTP version is 0.9, which only supports the transmission of plain text HTML files. Later, with the popularity of the Internet, HTTP gradually developed and upgraded to HTTP/1.0 and HTTP/1.1 versions. They add many new features, including support for multiple media types, support for persistent connections, and support for caching.

After HTTP/1.1, some new technologies also emerged. The most important of these is HTTPS, or HTTP Secure. HTTPS protects the security of HTTP communications through encryption and authentication technology. In addition, HTTP/2 has also been widely used in recent years. HTTP/2 adopts a new binary protocol to improve performance and efficiency.

How HTTP works

HTTP is based on the client-server model. When a user enters a URL into the browser and sends a request, the browser acts as a client and sends the request to the server. After the server receives the request, it will process it according to the content of the request and send the response back to the client.

HTTP uses a request-response model. A request consists of four parts: request line, request header, blank line and request body. The request line includes the request method, URL, and protocol version. The request header contains some additional information about the request, such as Accept, User-Agent, etc. Blank lines are used to separate request headers and request bodies. The request body contains some optional request data, such as form data or uploaded files.

After the server receives the request, it will process it according to the content of the request and generate a response. The response also consists of four parts: status line, response headers, empty line, and response body. The status line contains the response status code and status information. The response header contains some additional information about the response, such as Content-Type, Content-Length, etc. A blank line is used to separate response headers and response body. The response body contains the data returned by the server, such as HTML pages or images.

Application of HTTP

HTTP is one of the basic protocols of the World Wide Web. It is widely used in web browsing, email, file transfer, multimedia streaming and other scenarios.

In web browsing, users use the browser to send HTTP requests to access web pages. After receiving the request, the server returns corresponding HTML, CSS, JavaScript and other files, and the browser parses these files and displays them to the user. Through HTTP, users can quickly and easily access various web pages on the Internet.

In email, HTTP is used to transfer mail between the client and the mail server. Users can send and receive emails using the HTTP protocol, such as using Webmail services.

In file transfer, HTTP is used to upload and download files. Users can upload files to or download files from the server via HTTP.

HTTP is also used in multimedia streaming. Users can watch online videos or listen to online music in the browser via HTTP.

Summary

HTTP is the Hypertext Transfer Protocol, used to transfer hypertext data between clients and servers. It is one of the basic protocols of the World Wide Web and is widely used in web browsing, email, file transfer, multimedia streaming and other scenarios. As the Internet develops, the HTTP protocol continues to evolve, and new technologies are adopted to improve performance and security.

The above is the detailed content of What is HTTP?. For more information, please follow other related articles on the PHP Chinese website!