HTTP request header information explained

The HTTP message includes the client's request message to the server and the server's response message to the client. These two types of messages consist of a starting line, one or more header fields, a blank line that is just the end of the head field, and an optional message body. The header fields of HTTP include the general header, the request header, the response header, and the four parts of the entity header. Each header field consists of a domain name, a colon (:), and a domain value of three parts.

1. HTTP request mode

GET	Request a file from a Web server
POST	Send data to the Web server for processing by the Web server
PUT	Send data to the Web server and store it inside the Web server
HEAD	Checks if an object exists
DELETE	Delete a file from the Web server
CONNECT	Providing support for channels
TRACE	Trace the path to the server
OPTIONS	Querying the performance of a Web server

Note: The usual is get and post

2. Host

The requested Web server domain name address

3, User-agent

Details of the browser type that the HTTP client is running. With this header information, the Web server can determine the type of browser for the HTTP request client.

4. Accept

Specify the types of content that clients can receive, and the order in which the content types are received by the customer

5, Accept-lanuage

Specifies the language that the HTTP client browser uses to display the return information preference

6, Accept-encoding

Specifies that the Web server that the client browser can support returns the content compression encoding type. Indicates that the server is allowed to compress the output before it is sent to the client to conserve bandwidth. The return compression format that the client browser can support is set here.

7, Accept-charset

The set of character encodings acceptable to the HTTP client browser

8, Content-type

Displays the content type submitted by this HTTP request. This property is typically only required for post submission

There are two types of encoding for the Content-type attribute value:

(1) "application/x-www-form-urlencoded": the type of encoding used when the form data is submitted to the server, the default value is "application/x-www-form-urlencoded". However, this encoding is inefficient when sending large amounts of text to the server, including text or binary data that contains non-ASCII characters.

(2) "Multipart/form-data": When the file is uploaded, the type of encoding used should be "Multipart/form-data", which can both send text data and support binary data upload.

You can use "application/x-www-form-urlencoded" when committing to form data, and when you commit a file, you need to use the "multipart/form-data" encoding type.

9, Keep-alive

Indicates whether a persistent connection is required. If the Web server side sees the value here as "keep-alive", or if the request uses an HTTP 1.1 (HTTP 1.1 defaults to persistent connection), it can take advantage of the persistent connection

10, Response part

Header	explain	Example
Accept-ranges	Indicates whether the server supports the specified range request and what kind of staging request	Accept-ranges:bytes
Age	Estimated time (in seconds, non-negative) from the original server to the proxy cache	Age:12
Allow	A valid request behavior for a network resource is not allowed to return 405	Allow:get, HEAD
Cache-control	Tell if all caching mechanisms can be cached and which type	Cache-control:no-cache
Content-encoding	The type of return content compression encoding supported by the Web server.	Content-encoding:gzip
Content-language	The language of the response body	Content-language:en,zh
Content-length	The length of the response body	content-length:348
Content-location	Alternate alternative address to request resource substitution	Content-location:/index.htm
Content-md5	Returns the MD5 checksum value of a resource	content-md5:q2hly2sgsw50zwdyaxr5iq==
Content-range	The byte position of this section in the entire return body	Content-range:bytes 21010-47021/47022
Content-type	Returns the MIME type of the content	content-type:text/html; Charset=utf-8
Date	Time the original server message was issued	Date:tue, 08:12:31 GMT
ETag	The current value of the entity label of the request variable	ETag: "737060cd8c284d8af7ad3082f209582d"
Expires	Date and time when the response expires	Expires:thu, 16:00:00 GMT
Last-modified	Requested last modified time for resource	Last-modified:tue, 12:45:26 GMT
Location	Used to redirect the receiver to the location of the non-request URL to complete the request or identify the new resource	Location:http://www.zcmhi.com/archives/94.html
Pragma	Includes implementing a specific instruction that can be applied to any receiver on the response chain	Pragma:no-cache
Proxy-authenticate	It indicates the authentication scheme and the parameters on the URL that can be applied to the proxy	Proxy-authenticate:basic
Refresh	Applied to redirect or a new resource was created, redirected after 5 seconds (proposed by Netscape, supported by most browsers)	Refresh:5; Url=http://www.zcmhi.com/archives/94.html
Retry-after	Notifies the client to try again after a specified time if the entity is temporarily undesirable	retry-after:120
Server	Web Server Software Name	server:apache/1.3.27 (Unix) (Red-hat/linux)
Set-cookie	Set HTTP Cookies	Set-cookie:userid=johndoe; max-age=3600; Version=1
Trailer	Indicates that the header domain is present at the end of the chunked transfer code	Trailer:max-forwards
Transfer-encoding	File transfer encoding	Transfer-encoding:chunked
Vary	Tells the downstream agent whether to use the cache response or request from the original server	Vary: *
Via	Tells the proxy client where the response was sent by	via:1.0 Fred, 1.1 nowhere.com (apache/1.1)
Warning	Warning about possible issues with the entity	warning:199 Miscellaneous Warning
Www-authenticate	Indicates the authorization scheme that the client request entity should use	Www-authenticate:basic

HTTP request header information explained