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Understand the basic history and knowledge of HTTP

2022-04-29 12:16:48【InfoQ】

1990 Years ago

Before the 1990s , The Internet has not been invented yet , At that time, the Internet basically sent e-mail （Email1965 The invention of ） And other forms are simple and practical

1990 Years later, the world

Tim Berners-Lee（ Hereinafter referred to as Sir Lee ） stay 1989 - 1992 Year , Invented WWW（World Wide Web）

It mainly includes three concepts
URI, Commonly known as the website
HTTP, A protocol for transferring content between two computers
HTML, Hypertext , Mainly used to do page Jump
URL The function of is to let you visit a page ,HTTP The function of is to let you download this page ,HTML The function of is to let you understand this page
Perfect match, not tired to work

In addition to inventing these concepts , also ：
Invented the first server
Invented the first browser
Wrote the first web page
He won the most prestigious award in the field of computer science —— Turing Award
The father of the World Wide Web Tim Berners-Lee Turing award ： Bonus 100 Thousands of dollars （ Click to view the award information ）

URI（Uniform Resource Identifier）

Is a string used to identify the name of an Internet resource URI It is divided into URL and URN, We usually use URL As web address

URN（ Uniform resource code ）
ISBN: 9787115275790 It's just one. URN, adopt URN You can be sure of one 「 Unique 」 resources ,ISBN: 9787115275790 The corresponding resource is 《JavaScript Advanced programming （ The third edition ）》 This book . You're going to introduce any library 、 The bookstore , They all know it's this book .

URL（ Uniform resource locator ）
adopt URL You can be sure of one 【 Unique 】 Address （ website ）

First level domain name com Two level domain name baidu Three level domain name www

www.baidu.com

DNS

Enter the domain name

Output IP

Server + Client + HTTP

The browser is responsible for initiating the request, and the server is in 80 The port receiving request server is responsible for returning the content （ Respond to ） The browser is responsible for downloading the response content HTTP The role of is to guide the browser （Clinet） And the server （Server） How to communicate

Request example

1.url -s -v -H "Frank: xxx" -- "https://www.baidu.com" The requested content is

GET / HTTP/1.1

Host: www.baidu.com

User-Agent: curl/7.54.0

Accept: */*

Frank: xxx

curl -X POST -s -v -H "Frank: xxx" -- "https://www.baidu.com" The requested content is

POST / HTTP/1.1

Host: www.baidu.com

User-Agent: curl/7.54.0

Accept: */*

Frank: xxx

Format of request

1  Verb   route   agreement / edition 

2 Key1: value1

2 Key2: value2

2 Key3: value3

2 Content-Type: application/x-www-form-urlencoded

2 Host: www.baidu.com

2 User-Agent: curl/7.54.0

3

4  Data to upload

The request consists of at most four parts , There are at least three parts .（ That is to say, the fourth part can be empty ） The third part is always a carriage return （\n） Verb has  GET POST PUT PATCH DELETE HEAD OPTIONS The path here includes 「 Query parameters 」, But does not include 「 Anchor point 」( The anchor point is viewed by the browser , The server doesn't see ) If you don't write the path , So the default path is / The first 2 In section Content-Type Marked the 4 Part of the format

use Chrome Send the request

open Network Enter the web address in the address bar Network Click on , see request, Click on 「view source」 Click on 「view source」 Click on 「view source」 Click on 「view source」 Finally ordered ？ You can see the first three parts of the request. If there is a fourth part of the request , So in FormData or Payload You can see it in it

Respond to

Format of response

1  agreement / Version number   Status code   State interpretation 

2 Key1: value1

2 Key2: value2

2 Content-Length: 17931

2 Content-Type: text/html

3

4  What to download

The status code should be memorized , It's what the server says to the browser

1xx Not commonly used

2xx It means success

3xx Go away

4xx It means you are wrong

5xx Say ok , I was wrong

Status code query

use Chrome View the response

open Network Enter the URL and select the first response to view Response Headers, Click on 「view source」, Click on 「view source」, Click on 「view source」 You will see the first two parts of the response Response perhaps Preview, You'll see the response number 4 part

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