HTTP request, Response message format

HTTP Request message Format:

The HTTP request message consists of a request line, a request header, and a 3 part of the request body.

1, Request line

Consists of 3 parts: The request method, the URL (see note 1), and the protocol version, separated by a space

The request method includes, PUT, POST, TRACE, OPTIONS, delete, and extension methods, not all of which are implemented by all servers, and some of which are not available for security purposes even if supported

The format of the protocol version is: http/major version number. Minor version number, commonly used with http/1.0 and http/1.1

2, request the head

The request header adds some additional information to the request message, consisting of a "name/value" pair, separated by a colon between the name and the value, with each row.

Common request headers are as follows:

Request Header	Description
Host	The server address to accept the request, either IP: port number or domain name
User-agent	The application name that sent the request
Connection	Specify the properties associated with the connection, such as Connection:keep-alive
Accept-charset	Notifies the service side of the encoding format that can be sent
Accept-encoding	Notifies the server that a data compression format can be sent
Accept-language	Notifies the server which languages can be sent

There is a blank line at the end of the request header, which means that the request header ends and the request body is next, which is important and essential

3, Request body

An optional part, such as a GET request, has no request body

Get Request Example:

Example of a POST request:

HTTP Response message Format:

The HTTP response message consists of a status line, a response header, and a 3 part of the response body.

1, status line

Consists of 3 parts, namely: protocol version, Status code, status code description, separated by a space

The status code is 3 digits, the 200~299 state code indicates success, 300~399 status code refers to the resource redirection, 400~499 status code refers to the client request error, 500~599 status code refers to the server error (http/1.1 introduced an informational status code to the protocol, the range is 100 ~199)

Here are a few common examples:

tr>

	description
200	response succeeded
302	jump, The jump address is specified by the Location property in the response header (the difference between forward and redirect in the JSP)
400	client request syntax error, cannot be recognized by server
	server received request, but refused service (authentication failed)
404	request resource does not exist
500	server internal error

2, Response head

Similar to the request header, adds some additional information to the response message

Common response headers are as follows:

Response header	Description
Server	Name and version of the server application software
Content-type	The type of the response body (whether it is a picture or a binary string)
Content-length	Response Body Length
Content-charset	Encoding used by the response body
Content-encoding	Data compression format used by the response body
Content-language	Language used in response body

Response Example:

Ps:

The difference between 1,uri, url, and urn

The URI full name is uniform Resource indentifier (Uniform Resource Identity), which uniquely identifies a resource, is a common concept, and the URI consists of two main subset URLs and urns

The URL full name is uniform Resource Locator (Uniform Resource positioning), identifying the resource by describing the location of the resource

The urn full name is uniform Resource name (Uniform Resource naming), which identifies the resource by its name, regardless of where it is located, so that its urn does not change even if the location of the resource is changed

The HTTP specification takes a more generic conceptual URI as its resource identifier, but in fact, the HTTP application handles only a subset of the URI's URL

HTTP request, Response message format