Shulou(Shulou.com)06/01 Report--

The protocol is the rule that both sides of the communication in the network should follow. The Internet provides us with a variety of services, such as Web, eMail, FTP and so on. Each service needs to be implemented through the corresponding protocol, in which the Web service uses the HTTP protocol.

HTTP Hypertext transfer Protocol, which specifies the rules that clients (browsers) and Web servers (Web services) should follow to communicate with each other.

The HTTP protocol follows the request (Request) / response (Responses) model, and all HTTP communications are constructed as a pair of HTTP requests and HTTP responses. HTTP requests can only be initiated by the client, and the server cannot actively send data to the client. When the client sends a request to the Web server through the browser, the Web server processes the request and returns the corresponding reply.

For example, we visit www.51cto.com and intercept it through Burpsuite. First, the HTTP request sent by the client is intercepted and sent to the Repeater module. After sending it out, you will receive the HTTP response returned by the server.

On the client side, HTTP requests are usually made through a browser, and the role of the browser is to render those HTML tags into an intuitive interface acceptable to human beings, otherwise it will be just a pile of code like the packets we intercepted through Burpsuite. In addition to browsers, HTTP requests can also be initiated on the client side with the help of tools, such as curl.

For the Web server side, such as a typical PHP dynamic website, it is mainly composed of three parts: Web service, PHP preprocessor, and database.

Web services refer to Apache, Nginx, etc., which are responsible for receiving and processing HTTP requests. A simple Web service can only respond to a static request for a static page, that is, if the client browser requests a static page, only the Web service is required to respond to the request If the browser requests a dynamic page, the Web service will entrust the PHP preprocessor to interpret and execute the PHP code of the dynamic page, generate the execution result as a HTML static page, and then return the static page to the client browser for display. When interpreting and executing PHP code, PHP preprocessor often needs to call or store data from the database.

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