The composition method of the HTTP request has been requested by the status code

An HTTP request is a request message from the client to the server side.

Include: In the first line of the message, the request method of the resource, the identifier of the resource, and the protocol used. Request messages from the client to the server include, in the first line of the message, the resource's request method, the resource identifier, and the protocol used.

The HTTP request information consists of 3 parts :
1 Request Method URI Protocol/version
2 Requests Header (request header)
3 Request Body

HTTP response
HTTP replies are similar to HTTP requests, and HTTP responses are made up of 3 parts :
1 Status line
2 response Header (Response header)
3 Response Body
After the request message is received and interpreted, the server returns an HTTP response message.
The status line consists of the Protocol version, the status code in the number form, and the corresponding status description, separated by a space between the elements.
Format: http-version status-code reason-phrase CRLF

methods for HTTP requests :

The http/1.1 protocol defines eight methods (sometimes called "actions") to indicate the different modes of operation of the Request-uri specified resources:

1GET　Make a request to a specific resource. Note: The Get method should not be used in operations that produce "side effects", such as in Web apps. One of the reasons is that get can be accessed by web spiders and other casual.

2POSTSubmits data to the specified resource for processing requests (such as submitting a form or uploading a file). The data is included in the request body. A POST request may result in the creation of new resources and/or modification of existing resources.
 　 
3PUTUploads its latest content to the specified resource location.

4DELETEThe requesting server deletes the resource identified by Request-uri.

5OPTIONSReturns the HTTP request methods that the server supports for a specific resource. You can also test the functionality of your server with a request to send a ' * ' to the Web server.

6HEADAsk the server for a response that is consistent with the GET request, except that the response body will not be returned. This method allows you to obtain meta information contained in the response message header without having to transmit the entire response content.

 7 TRACE echo the request received by the server, primarily for testing or diagnostics.

8 The Connect    http/1.1 protocol is reserved for proxy servers that can change connections to pipelines. 

HTTP status Code
1 Opening message
2 opening successes
3 Start redirect
4 Start request Error
5 6 Starting Server error
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The composition method of the HTTP request has been requested by the status code