No knowledge and no skills

Once again, I felt ignorant and incompetent. When someone asked me about HTTP knowledge, I didn’t have any answers. It was so embarrassing. I usually read a lot of technical articles, but why can’t I answer the question at the critical moment?

I did find a problem. Just looking at it is useless, it requires practice. I feel like I understand what others say clearly, but I find that if I ask myself to repeat it again, I may not be able to answer it at all. This is because reading other people's articles is more like reading a novel. You can follow the author's ideas in your mind and feel that you understand them well, but in fact they are just passing by. So I want to learn technology well

On the one hand, you need to read other people’s summaries, such as articles, books, and source codes
Then you have to summarize it yourself, such as writing a blog or running through the code in the book, so as to deepen your understanding.
The last thing is to use it, especially at work. If you have used a skill very skillfully, it will be difficult to forget it.

In order to give yourself a better impression of HTTP knowledge, write a blog. Start from the shallower to the deeper and take your time.

First, let’s get to know http briefly

HTTP is Hypertext Transfer Protocol, which is an application layer protocol. My understanding is that the server generates a piece of text and transmits it over the network, and the client can parse it into a view and provide interaction.

http is composed of requests and responses. It is a stateless protocol when designed, so that every operation is basically that the client initiates a request and the server returns a response.

Http requests and responses both include: request line, message header and message body.

Common Headers

Speaking of the header, it is not complicated, but if you take a closer look, there is a lot of knowledge in it, but it is indeed a bit much. The main thing is to focus on some common ones first.

Common header field

Cache-Control: Specify the caching mechanism followed by requests and responses
Connection:keep-alive:Keep the TCP connection with the server
Date: The date and time the message was sent
Pragma: used to contain implementation-specific instructions, the most commonly used is Pragma:no-cache. In the HTTP/1.1 protocol, its meaning is the same as Cache-Control:no-cache.
Transfer-Encoding:chunked: chunked encoding

Request Header

Request URL: Requested URL
Request Method: Request method (OPTIONS, HEAD, GET, POST, PUT, DELETE, TRACE, CONNECT, PATCH)
Remote Address: The address of the remote server
Accept: Specify the MIME type received by the client (text/html, application/xhtml+xml, application/xml)
Accept-Encoding: Specifies the encoding received by the client, usually used to specify the compression algorithm (gzip, deflate, sdch)
Accept-Language: Specify the language received by the client (zh-CN,zh)
Accept-Charset: Specify the character set received by the client (gb2312, uft-8)
Cookie: client cookie information
Host: Requested domain
User-Agent: User information that initiated the request, operating system, browser version, etc.
If-Modified-Since: The time when the server was last modified

response header

Content-Encoding: Response packet encoding and compression algorithm (gzip)
Content-Type: Resource type of response package (text/html; charset=utf-8)
Expires: Expiration time
Last-Modified: Last modified time

Common status codes

200: Request successful
201: The request has been fulfilled, and a new resource has been created based on the request, and its URI has been returned with the Location header information
301/302: Redirect
304: The resource requested by the client has not been modified
400: Bad request package
404: Request failed, the specified resource was not found
500: Internal server error, usually the server has an error and cannot return a response packet

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