http--Study notes (3)

HTTP message: For HTTP protocol interaction information, the client's HTTP message is called the request message, the response is called the response message

Essence: A string literal consisting of multirow (with Cr+lf as a newline character) data

Note: CR: Enter, print pin back to the beginning of the line LF: wrap, print pin move to next line

Composition: message header, message body

Message header: The content and properties of the request or response that the server side or client needs to process

Message body: Data to be sent

Request message (upper) response message (bottom)

Request line: Requested method, request URI, HTTP version

Status line: Response result status code, reason phrase, HTTP version

Header field: A variety of headers that represent the various conditions and attributes of a request and response, typically four types (see figure)

Other: Undefined header (cookie, etc.) in RFC containing HTTP

Encoding in HTTP

HTTP can transfer data directly, can also be encoded after the transfer, encoding method can effectively handle a large number of access requests, but the encoding process requires the computer to complete, and therefore consumes more CPU and other resources

Message: The basic unit of HTTP communication, consisting of 8-bit byte streams, transmitted via HTTP communication

Entity: Payload Data (supplementary item) as a request or response is transmitted, and its contents consist of the entity header and the entity body

The body of the message is used to transmit the entity body of the request or response, usually, the message body equals the entity body, and the content of the entity body is changed only when it is encoded in the transmission, which causes it to differ from the message body.

Content encoding in HTTP keeps the entity information compressed as it is, and the content-encoded entities are received by the client and are responsible for decoding

Common content Encoding: gzip Compress deflate identity (not coded)

Transmission encoding mechanism: transmitted in a coded manner during communication, but only defined in the chunked transfer encoding

chunked transfer encoding: When transferring large volumes of data, by splitting the data into chunks, the browser is able to progressively display the page

MIME mechanism in mail: Multi-purpose Internet Mail extensions, support for sending multiple types of files, such as mail, text, pictures, videos, etc., because of the use of a method called a collection of multipart objects

Multi-Part object collection: HTTP also uses a multipart collection, sending a message body can contain a multi-type entity, which contains the following objects:

Multipart/form-data: Used when uploading Web Forms files

Multipart/byteranges: Status code 206 (partial content), when the response message contains multiple ranges of content when used

HTTP GET partial content request　

Add Range on request header to delimit request

Example: range:bytes=5001-10000 5001-10000 bytes

Range:bytes=5001-5001 to the back of all bytes

range:bytes=-3000,5000-7000 start to 3000 bytes and 5000 to 7000 bytes

Returns a 206 response message for a status code that returns a status code of OK and full entity content if the server is unable to respond to a range request

HTTP Content Negotiation

The same Web site may have more than the same content of the page, such as English and Chinese version, when the default language of the browser is English or Chinese, access to the same URI Web page will display the corresponding English or Chinese version of the page, such a mechanism called content negotiation

Benchmark: Response resource language, character set, encoding method, etc.

Header field: Accept

Accept-charset

Accept-encoding

Accept-language

Content-language

Technology for content negotiation:

Server-driven negotiation: content filtering by the server

Client-driven negotiation: content filtering by the client, manually selected by the user from the optional list, or using JavaScript to select

Transparent negotiation: Content negotiation by server side and client

http--Study notes (3)