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Today, the editor will take you to understand what the http in front of the website address refers to. The knowledge points in the article are introduced in great detail. Friends who feel helpful can browse the content of the article together with the editor, hoping to help more friends who want to solve this problem to find the answer to the problem. Let's follow the editor to learn more about "what is the http in front of the website address".

What is HTTP?

When we want to visit a website, just enter the address of the website in the address bar of the browser, such as www.yisu.com, but what appears in the address bar of the browser is: https://www.yisu.com, do you know why there is an extra "http"?

What is the HTTP protocol?

The address of the website we entered in the browser's address bar is called URL (Uniform Resource Locator, uniform Resource Locator). Just like every home has a house address, every web page has an Internet address. When you type a URL in the browser's address box or click a hyperlink, URL determines the address to browse. The browser uses Hypertext transfer Protocol (HTTP) to extract the web page code of the site on the Web server and translate it into beautiful web pages. Therefore, before we know HTTP, it is necessary to know the composition of URL, such as https://www.yisu.com. Its meaning is as follows:

1. Http://: stands for Hypertext transfer Protocol, which tells the microsoft.com server to display Web pages, usually without typing

2. Www: represents a Web (World wide Web) server

3. Microsoft.com/: this is the domain name of the server with the web page, or the name of the site server

4. China/: is a subdirectory on the server, just like our folder

5. Index.htm:index.htm is a HTML file (web page) in a folder.

We know that the basic protocol of Internet is the TCP/IP protocol, but the top layer of the TCP/IP model is the application layer (Application layer), which contains all the high-level protocols. The high-level protocols include: file transfer protocol FTP, e-mail transfer protocol SMTP, domain name system service DNS, network news transfer protocol NNTP and HTTP protocol.

HTTP protocol (Hypertext Transfer Protocol, Hypertext transfer Protocol) is a transport protocol used to transfer hypertext from a WWW server to a local browser. It can make browsers more efficient and reduce network transmission. It not only ensures that the computer transmits hypertext documents correctly and quickly, but also determines which part of the transferred document and which part of the content is displayed first (for example, text precedes graphics) and so on. That's why all the web addresses you see in browsers start with http://.

Since the birth of WWW, a colorful information and virtual world has appeared in front of us, but how can we find the information we need more easily? When it was decided to use hypertext as the standard format for WWW documents, in 1990, scientists immediately developed a protocol to quickly find these hypertext documents, the HTTP protocol. After several years of use and development, it has been continuously improved and expanded. At present, the sixth edition of HTTP/1.0 is used in WWW.

How does HTTP work

Now that we understand the composition of URL, how does HTTP work? We are going to discuss this problem next.

Because the HTTP protocol is based on the request / response paradigm (equivalent to client / server). After a client establishes a connection with the server, it sends a request to the server in the format of uniform Resource Identifier (URL), protocol version number, followed by MIME information including request modifiers, client information, and possible content. After receiving the request, the server gives the corresponding response information in the format of a status line, including the protocol version number of the information, a success or error code, followed by MIME information, including server information, entity information and possible content.

Many HTTP communications are initialized by a user agent and include a request for resources on the source server. The simplest case is probably done through a separate connection between the user agent and the server. On Internet, HTTP communication usually occurs over a TCP/IP connection. The default port is TCP 80, but other ports are also available. But this does not mean that the HTTP protocol can only be completed on top of Internet or other protocols of other networks. HTTP only heralds a reliable transmission.

This process is like making a phone call to place an order. We can call the merchant and tell him what specifications we need, and then the merchant will tell us what goods are in stock and what are out of stock. We communicate with each other by telephone through the telephone line (HTTP is through TCP/IP). Of course, we can also use fax, as long as there is a fax from the merchant.

The above briefly introduces the macro operation of the HTTP protocol, and the following describes the internal operation process of the HTTP protocol.

In WWW, "client" and "server" are a relative concept that exists only during a specific connection, that is, a customer in one connection may act as a server in another connection. The information exchange process of client / server mode based on HTTP protocol, which is divided into four processes: establishing connection, sending request information, sending response information, and closing connection. This is like the example above, the whole process of ordering by phone.

To put it simply, in addition to HTML files, any server also has a HTTP resident program that responds to user requests. Your browser is a HTTP client and sends a request to the server. When the browser enters a start file or clicks a hyperlink, the browser sends a HTTP request to the server, which is sent to the URL specified by the IP address. The resident program receives the request and sends back the requested file after performing the necessary operation. In this process, the data sent and received on the network has been divided into one or more data packets (packet), each packet including: data to be transmitted; control information, that is, telling the network how to process the data packet. TCP/IP determines the format of each packet. If you don't tell you in advance, you may not know that the information is divided into many small pieces for transmission and reassembly.

That is to say, in addition to the merchandise, it also has an employee answering your phone. When you make a call, your voice is converted into all kinds of complex data, which is transmitted to the other party's phone through the telephone line. The other party's phone converts all kinds of complex data into sound, so that the staff of the other side's business can understand your request. You don't need to understand how sound is converted into complex data in this process.

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