Explanation of HTTP request header information

Explanation of HTTP request header information

HTTP messages include request messages from the client to the server and response messages from the server to the client. Both types of messages consist of a start line, one or more header fields, a blank line that just ends the header fields, and an optional message body. The HTTP header field includes four parts: general header, request header, response header and entity header.

Each header field consists of a domain name, a colon (:) and a field value.

1. HTTP request method

GET	Request a file from the web server
POST	Send data to the web server for the web server to process
PUT	Send data to the web server and store inside the web server
HEAD	Check if an object exists
DELETE	Delete a file from the web server
CONNECT	Provide support for channels
TRACE	Trace the path to the server
OPTIONS	Query the performance of the web server

Note: GET and POST are commonly used

2、Host

The domain name address of the requested web server

3、User-Agent

Details of the type of browser the HTTP client is running. Through the header information, the web server can determine the browser type of the client of the http request.

4、Accept

Specifies the content types that the client can receive. The order of the content types indicates the order in which the clients receive them.

5、Accept-Lanuage

Specifies the preferred language for HTTP client browsers to display returned information

6、Accept-Encoding

Specifies the content compression encoding type returned by the web server that the client browser can support. Indicates that the server is allowed to compress the output before sending it to the client to save bandwidth. What is set here is the return compression format that the client browser can support.

7、Accept-Charset

The set of character encodings accepted by HTTP client browsers

8、Content-Type

Displays the content-type submitted by this HTTP request. Generally, this property only needs to be set when the post is submitted.

There are two encoding types for the Content-Type property value:

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

(2) "multipart/form-data": When uploading files, the encoding type used should be "multipart/form-data", which can send both text data and binary data upload.

When submitting as form data, you can use "application/x-www-form-urlencoded"; when submitting as a file, you need to use "multipart/form-data" encoding type.

9、Keep-Alive

Indicates whether a persistent connection is required. If the web server sees the value here as "Keep-Alive", or sees that the request is using HTTP 1.1 (HTTP 1.1 defaults to persistent connections), it can take advantage of persistent connections

10. Response section

Header	explain	Example
Accept-Ranges	Indicates whether the server supports the specified range request and what type of segment request	Accept-Ranges: bytes
Age	Estimated time from origin server to proxy cache formation (in seconds, non-negative)	Age: 12
Allow	Valid request behavior for a network resource, if not allowed, return 405	Allow: GET, HEAD
Cache-Control	Tell all caching mechanisms if they can be cached and which type	Cache-Control: no-cache
Content-Encoding	The returned content compression encoding type 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	Requesting an alternate alternate address for the resource	Content-Location: /index.htm
Content-MD5	Returns the MD5 checksum of the resource	Content-MD5: Q2hlY2sgSW50ZWdyaXR5IQ==
Content-Range	the byte position of this part 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	The time the origin server message was sent	Date: Tue, 15 Nov 2010 08:12:31 GMT
ETag	The current value of the entity tag of the request variable	ETag: “737060cd8c284d8af7ad3082f209582d”
Expires	Date and time when the response expires	Expires: Thu, 01 Dec 2010 16:00:00 GMT
Last-Modified	The last modification time of the requested resource	Last-Modified: Tue, 15 Nov 2010 12:45:26 GMT
Location	Used to redirect the recipient to an unrequested URL to complete the request or identify a new resource	Location: http://www.zcmhi.com/archives/94.html
Pragma	Includes implementation-specific directives that apply to any recipient in the response chain	Pragma: no-cache
Proxy-Authenticate	It indicates the authentication scheme and parameters that can be applied to the proxy on this URL	Proxy-Authenticate: Basic
refresh	Applied to redirects or a new resource is created, redirects after 5 seconds (proposed by Netscape, supported by most browsers)	Refresh: 5; url=http://www.zcmhi.com/archives/94.html
Retry-After	If the entity is temporarily unavailable, notify the client to try again after the specified time	Retry-After: 120
Server	web server software name	Server: Apache/1.3.27 (Unix) (Red-Hat/Linux)
Set-Cookie	Set HttpCookie	Set-Cookie: UserID=JohnDoe; Max-Age=3600; Version=1
Trailer	Indicates that the header field exists at the end of the chunked transfer encoding	Trailer: Max-Forwards
Transfer-Encoding	file transfer encoding	Transfer-Encoding:chunked
Vary	Tell downstream proxies whether to use cached responses or request from origin servers	Vary: *
Via	Tell the proxy where the client response is sent	Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1)
Warning	Warn entities of possible problems	Warning: 199 Miscellaneous warning
WWW-Authenticate	Indicates the authorization scheme that the client requesting entity should use	WWW-Authenticate: Basic