HTTP network communication protocol

 

table of Contents

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 Reserve knowledge

HTPPBefore explaining the protocol, first understand some basic computer network related knowledge

1.1 Computer network architecture

• Define 
  each layer of the computer network + its set of protocols

• The role
  defines the functions  that the computer network can perform

• Structure Introduction 
  Computer network architecture is divided into 3 types: OSIarchitecture, TCP /  IParchitecture, five-tier architecture

• OSIArchitecture: clear concept & complete concept, but complex & impractical

• TCP /  IPArchitecture: Contains a series of network protocols that form the basis of the Internet, is Internetthe core protocol & is widely used in local area networks and wide area networks

• Five-tier architecture: The architecture that combines OSI and  TCP /  IPis designed to learn & explain the principles of computers

• TCP / IPThe architecture of /  is introduced in detail 
  because  TCP /  IParchitecture is more extensive, so the main explanation 
  

1.2 The basic model of HTTP protocol communication

• HTTPThe basis of protocol transmission information: TCP/IPprotocol model 
  

• HTTPThe protocol belongs to the highest application layer

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 Introduction

Below, I will briefly introduce HTTP

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Way of working

• HTTPThe protocol uses a request / response working method

• The specific workflow is as follows:

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Detailed HTTP message

• HTTPWays to interact with data at the application layer = message

• HTTPThe message is divided into: request message & response message 

  Used to send requests & respond to requests, respectively

• Below, the two types of messages will be introduced in detail

4.1 Request message

4.1.1 Message structure

• HTTPThe request message consists of request line, request header & request body, as shown in the figure below

• Below, each component will be described in detail

4.1.2 Detailed structure introduction

Composition 1: request line

• Function 
  declaration request method, host domain name, resource path & protocol version

• 
  Composition of structure  request line = request method + request path + protocol version

  Note: Spaces cannot be saved

• Composition Introduction

The difference between GET and PSOT methods is specifically explained here:

• Example 
  design: request message adopting GETmethod,  URLaddress = http://www.tsinghua.edu.cn/chn/yxsz/index.htm; HTTP1.1version

The request line is:GET /chn/yxsz/index.htm HTTP/1.1

Composition 2: Request header

• Function: declare some information of client, server / message

• How to use: Use "header (field name): value (value)"

• Common request headers
  1. Common headers for  request and response messages

2. Common Request Header

• Example: 
  (URL address: http://www.tsinghua.edu.cn/chn/yxsz/index.htm) 
  Host: www.tsinghua.edu.cn (indicating host domain name) 
  User-Agent: Mozilla / 5.0 (indicating user Agent is using Netscape browser)

Composition 3: Request body

• Role: to store the data information to be sent to the server

  Optional part, if  GET请求no data is requested

• Usage: 3 kinds in total

So far, the request line, request header, and request body of the request message are all explained.

4.1.3 Summary

• The summary of the request message is as follows

• Request message example

4.2 HTTP response message

4.2.1 Message structure

• HTTPResponse message includes: status line, response header & response body

• Among them, the response header and response body are similar to the request header and request body of the request packet

• The biggest difference between these two types of messages is the status line & request line

Below, each component will be described in detail

4.2.2 Detailed structure introduction

Composition 1: Status line

• Function 
  statement protocol version, status code, status code description

• The composition
  status line is composed  of protocol version, status code & status information 

  Among them, spaces cannot be saved

• Specific introduction 
  

• Status line example 
  HTTP/1.1 202 Accepted(accepted), HTTP/1.1 404 Not Found(not found)

Composition 2: Response header

• Function: declare some information of client, server / message

• How to use: Use "header (field name): value (value)"

• Common request headers
  1. Common headers for  request and response messages

2. Common Response Header

Composition 3: Response body

• Role: store the data information that needs to be returned to the client

• Usage: It is consistent with the request body, and is also divided into: any type of data exchange format, key-value pair form and partial form

4.2.3 Summary of response messages

4.3 Summary

Below, a brief summary of the two message structures 

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Additional knowledge

The following will explain some HTTPadditional knowledge:

• HTTP1.1 With  HTTP1.0 distinction

• HTTP With  HTTPSdistinction

• HTTP Ways to handle long connections

5.1 Differences between HTTP1.1 and HTTP1.0

Http1.1 Compared  Http1.0 with the following advantages:

• Introduce persistent connections, that is TCP, multiple HTTPrequests & responses can be transmitted in the same connection

• Multiple requests & responses can be performed simultaneously and can be overlapped

• Introduce more request headers & response headers 

 

No fields such as those related to authentication, state management &  Cachecaching, etc.HTTP1.0host

5.2 The difference between HTTP and HTTPS

5.3 How HTTP handles long connections