[Http] the http method, status code, and composition.

[Http] the http method, status code, and composition.
Http (Hypertext Transfer Protocol)

HyperText Transfer Protocol (Hyper Text Transfer Protocol) is a Transfer Protocol used to Transfer HyperText from a WWW server to a local browser. It makes the browser more efficient and reduces network transmission. It not only ensures that the computer transfers hypertext documents correctly and quickly, but also determines which part of the transmitted documents and which part of the content is first displayed (such as text before graphics.

The information used for http protocol interaction is called http packets. The http packet of the request end (client) is called the request message, and the http packet of the response end (server) is called the Response Message.

The Request Message consists of the Request Method, request URI, Protocol version, header field (optional), and content entity (optional ).

The Response Message consists of the Protocol version, status code, cause phrase, header field (optional), and entity.

 

In each packet, the request URI, Protocol version, status code, reason phrase, and header field belong to the packet header, and then empty a line. The rest is the packet subject.

There are four types of header fields: request header field, response header field, General header field, entity header field, and general header and entity header are available in both request message and Response Message, the request header only contains the request message, and the response header only contains the Response Message.

 

A packet is a basic unit in http Communication. It consists of eight byte streams and is transmitted over http.

The entity is transmitted as the request and response payload data (Supplemental item). Its content consists of the entity header and entity body.

Generally, the message body is equal to the entity body. The content of the entity body changes only when the encoding operation is performed during transmission, which is inconsistent with the message body.

 

Methods supported by http1.0 and http1.1

Method	Description	Supported http versions
GET	Obtain a resource identified by a URI	1.0, 1.1
POST	Transmission entity	1.0, 1.1
PUT	Transfer file (without verification mechanism)	1.0, 1.1
HEAD	Obtain the packet header	1.0, 1.1
DELETE	Delete files (without authentication mechanism)	1.0, 1.1
OPTIONS	Question Support Method	1.1
TRACE	Tracing path	1.1
CONNECT	Require a tunneling protocol connection proxy	1.1
LINK	Establish connections with resources	1.0
UNLINK	Disconnected	1.0

 

 

 

Http status code

Status Code	Category	Reason phrase
1XX	Informational (Information Status Code)	The received request is being processed.
2XX	Success (Success status code)	Request processed
3XX	Redirection (Redirection status code)	Additional operations are required to complete the request
4XX	Client Error (Client Error status code)	The server cannot process the request.
5XX	Server Error (Server Error status code)	An error occurred while processing the request on the server.

 

Common status codes in 14

200 OK	The request sent from the client is processed properly on the server.
204 No Content	Indicates that the request received by the server has been processed successfully, but the returned response message does not include the entity body.
206 Partial Content	Indicates that the client has performed a range request, and the server has successfully executed the GET request.
301 Moved Permaently	Permanent redirection indicates that the requested resource has been assigned a new URI, and the requested resource URI should be used later
302 Found	Temporary redirection indicates that the requested resource has been assigned a new URI.
303 See Other	Indicates that the requested resource should be obtained using the GET method because the resource corresponding to the request has another URI.
304 Not Modified	Indicates that when the client sends a conditional request, the server allows the request to access the resource. However, if the request meets the conditions, 304 Not Modified is returned directly (the server resource is changed, you can directly use the principal part that has not expired on the client)
307 Temporary Redirect	Temporary redirection, which has the same meaning as 302
400 Bad Request	Indicates a syntax error in the request message. The server cannot identify the request
401 Unauthorized	Indicates the authentication information for the request to pass http authentication. If a request has been made before, the user authentication fails.
403 Forbidden	Indicates that access to the requested resource is rejected by the server. No access permission
404 Not Found	Indicates that the server cannot find the requested resource, that is, the requested resource does not exist.
500 Internal Server Error	Indicates that an error occurs when the server executes the request, or a web application may have a bug or some temporary faults.
503 Service Unavailable	Indicates that the server is temporarily overloaded or is being shut down for maintenance, and the request cannot be processed now

 

 

Http common header field

Common header field name	Description
Cache-Control	Control cache behavior
Connection	Manage skip-by-hop headers and persistent connections
Date	The date and time when the message was created.
Pragma	Message instructions
Trailer	Overview of the header at the end of the message
Transfer-Encoding	Transmission Encoding Method of the specified message body
Upgrade	Upgrade to another protocol to check whether higher version protocol communication is available
Via	Information about the proxy server, tracing the transmission path of request and response packets between the client and the server
Warning	Error Notification, which usually notifies users of warnings about cache-related problems.

 

Http1.1 Warning codes (seven Warning types)

Warning code	Warning content	Description
110	Response is stale (Response has expired)	The proxy returns expired resources.
111	Revalidation failed (re-verification failed)	An error occurred while the agent was unable to verify the resource validity (the server could not arrive, and other reasons)
112	Disconnection operation)	The proxy and Internet connection are deliberately cut off
113	Heuristic expiration (tentative expiration)	Response validity period exceeds 24 hours (when the effective cache is set to be greater than 24 hours)
199	Miscellaneous warning (Miscellaneous warning)	Any warning content
214	Tansformation applied (conversion is used)	When the proxy processes Content Encoding or media types
299	Miscellaneous persistent warning (persistent Miscellaneous warning)	Arbitrary warning content

 

 

Http request header field

Request Header field	Description
Accept	Media types that the user agent can process and their relative priority
Accept-Charset	Priority Character Set, Character Set supported by the user agent, and relative priority
Accept-Encoding	Priority encoding, Content Encoding supported by the user agent, and priority order
Accept-Language	Preferred language, the natural language that the user agent can process, and the relative priority of the Natural Language Set
Authorization	Web authentication information
Secondary CT	Expect specific server Behavior
From	User's email address
Host	Server where the requested resource is located (host name and port number)
If-Match	Compared with the object tag (ETag), if the request is the same, the request is executed. Otherwise, the 412 status code is returned.
If-Modefied-Since	If the If-Modefied-Since field value is earlier than the resource Update time, you want to process the request. Otherwise, the 304 status code is returned.
If-None-Match	Compare object tags (reverse Match with If-Match)
If-Range	When the resource is not updated, the system sends a request for the object Byte range. If the If-Range field value is consistent with the ETag value or time of the requested resource, the request is processed as a Range request. Otherwise, all resources are returned.
If-Unmodified-Since	Compare the resource Update Time (If-Modified-Since wants to reverse)
Max-Forwards	Maximum number of hops for transmission (specify the maximum number of servers that can pass through in decimal format)
Proxy-Authorization	The proxy server requires client authentication information
Range	Object byte range request
Referer	The original accessor Of The URI in the request (the URI of the requested original resource)
TE	Inform the Server client of the Transmission Encoding Method and relative priority of the response.
User-Agent	Http client program information

 

 

Http response header field

Response Header field	Description
Accept-Ranges	Whether to accept byte range requests
Age	Resource Creation Time, in seconds
ETag	Resource matching information to notify the client entity ID
Location	Redirects the client to a specified URI
Proxy-Authenticate	Authentication information of the proxy server to the client
Retry-After	Requirements on the time when a request is initiated again
Server	Http Server installation information
Vary	Proxy Server Cache Management Information
WWW-Authenicate	Authentication information of the server to the client

 

 

Http object header field

Object header field	Description
Allow	Http methods supported by resources
Content-Encoding	Entity encoding method
Content-Language	Natural Language of Entity
Content-Length	Object size (in bytes)
Content-Location	Replace the URI of the corresponding resource
Content-MD5	Object Body message digest
Content-Range	Object subject location range
Content-Type	Media type of the Entity
Expires	Object subject expiration date and time
Last-Modified	Date and time when the resource was last modified