HTTP header details

HTTP (hypertexttransferprotocol) is the hypertext transfer protocol, which is currently a common protocol for webpage transmission. The HTTP protocol uses a request/response model. A browser or other client sends a request, and the server gives the response. The entire network resource transmission involves message-header and message-body. First pass the message-header, that isHTTP HeaderMessage.HTTP header messages are generally divided into four parts: General header, request header, response header, and entity header. However, in terms of understanding this method, I feel that the boundary is not clear. According to the content organization of HTTP headers in Wikipedia, the content is divided into two parts: request and response.

Requests

Header	Explanation	Example
Accept	Specifies the content type that the client can receive	Accept: text/plain, text/html
Accept-charset	String set that the browser can accept.	Accept-charset: iso-8859-5
Accept-Encoding	Specifies the type of content compression encoding that can be returned by the Web server supported by the browser.	Accept-encoding: compress, Gzip
Accept-Language	Acceptable browser Language	Accept-language: En, ZH
Accept-ranges	You can request one or more sub-range fields of a webpage object.	Accept-ranges: bytes
Authorization	HTTP Authorization Certificate	Authorization: Basic qwxhzgrpbjpvcgvuihnlc2ftzq =
Cache-control	Specify the cache mechanism for requests and responses	Cache-control: No-Cache
Connection	Indicates whether a persistent connection is required. (HTTP 1.1 performs persistent connections by default)	Connection: Close
Cookie	When an HTTP request is sent, all cookie values stored under the domain name of the request are sent to the web server.	COOKIE: $ version = 1; Skin = new;
Content-Length	Request Content Length	Content-Length: 348
Content-Type	Mime information of the request corresponding to the object	Content-Type: Application/X-WWW-form-urlencoded
Date	Date and time when the request was sent	Date: Tue, 15 Nov 2010 08:12:31 GMT
Secondary CT	Specific server behavior of the request	Secondary CT: 100-continue
From	Email of the user sending the request	From: [email protected]
Host	Specify the domain name and port number of the requested Server	HOST: www.zcmhi.com
If-match	Valid only when the request content matches the object	If-Match: "737060cd8c284d8af7ad3082f209582d"
If-modified-since	If the request is modified after the specified time, the request is successful. If the request is not modified, code 304 is returned.	If-modified-since: sat, 29 Oct 2010 19:43:31 GMT
If-None-match	If the content is not changed, the system returns the 304 code. The parameter is the etag previously sent by the server. Compare it with the etag responded by the server to determine whether the etag is changed.	If-None-Match: "737060cd8c284d8af7ad3082f209582d"
If-Range	If the entity has not changed, the server sends the part lost by the client; otherwise, the whole entity is sent. The parameter is also etag.	If-range: "737060cd8c284d8af7ad3082f209582d"
If-unmodified-since	The request is successful only when the object is not modified after the specified time.	If-unmodified-since: sat, 29 Oct 2010 19:43:31 GMT
Max-forwards	Restrict the time when information is transmitted through the proxy and gateway	Max-forwards: 10
Pragma	Used to include specific instructions	Pragma: No-Cache
Proxy-Authorization	Connect to the proxy authorization certificate	Proxy-authorization: Basic qwxhzgrpbjpvcgvuihnlc2ftzq =
Range	Request only part of the object, specifying the range	Range: bytes = 500-999
Referer	The address of the previous webpage, followed by the current requested webpage.	Referer: http://www.zcmhi.com/archives/71.html
Te	The client is willing to accept the transfer code and notifies the server to accept the tail header information.	Te: trailers, deflate; q = 0.5
Upgrade	Specify a certain transmission protocol to the server for server conversion (if supported)	Upgrade: HTTP/2.0, shttp/1.3, IRC/6.9, RTA/X11
User-Agent	The User-Agent content contains the user information that sends the request.	User-Agent: Mozilla/5.0 (Linux; X11)
Via	Notify the intermediate gateway or proxy server address, communication protocol	Via: 1.0 Fred, 1.1 nowhere.com (Apache/1.1)
Warning	Message entity warning information	Warn: 199 miscellaneous warning

Responses Section

Header	Explanation	Example
Accept-ranges	Indicates whether the server supports specified range requests and the type of segmented requests	Accept-ranges: bytes
Age	Estimated time from the origin server to the proxy cache (in seconds, non-negative)	Age: 12
Allow	Valid request behavior for a network resource. If the request is not allowed, 405 is returned.	Allow: Get, head
Cache-control	Tell all cache mechanisms whether they can be cached or not	Cache-control: No-Cache
Content-Encoding	The compression encoding type of the returned content supported by the Web server.	Content-encoding: Gzip
Content-language	Response Body Language	Content-language: En, ZH
Content-Length	Response body length	Content-Length: 348
Content-location	Another alternative address that the requested resource can replace	Content-location:/index.htm
Content-MD5	Returns the MD5 checksum of the resource.	Content-MD5: q2hly2sgsw50zwdyaxr5iq =
Content-Range	Bytes in the whole returned body	Content-range: bytes 21010-47021/47022
Content-Type	Mime Type of returned content	Content-Type: text/html; charset = UTF-8
Date	Time when the original server message was sent	Date: Tue, 15 Nov 2010 08:12:31 GMT
Etag	Current Value of the object tag of the Request variable	Etag: "737060cd8c284d8af7ad3082f209582d"
Expires	Response expiration date and time	Expires: Thu, 01 Dec 2010 16:00:00 GMT
Last-modified	Last modification time of the requested resource	Last-modified: Tue, 15 Nov 2010 12:45:26 GMT
Location	Used to redirect the recipient to a location other than the requested URL to complete the request or identify a new resource	Location: http://www.zcmhi.com/archives/94.html
Pragma	Includes the implementation of specific commands that can be applied to any receiver on the response chain.	Pragma: No-Cache
Proxy-Authenticate	It specifies the authentication scheme and the parameters that can be applied to the URL of the proxy.	Proxy-Authenticate: Basic
Refresh	Apply to redirection or a new resource is created and redirected in 5 seconds (proposed by Netscape and supported by most browsers)	Refresh: 5, url = http://www.zcmhi.com/archives/94.html
Retry-after	If the object 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 HTTP cookie	Set-COOKIE: userid = johndoe; max-age = 3600; version = 1
Trailer	Indicates that the header field exists at the end of the multipart Transfer Encoding.	Trailer: Max-forwards
Transfer-Encoding	File Transfer Encoding	Transfer-encoding: chunked
Vary	Tell the downstream proxy whether to use cache response or request from the original server	Vary :*
Via	Tell the proxy client where the response is sent	Via: 1.0 Fred, 1.1 nowhere.com (Apache/1.1)
Warning	Warning possible entity Problems	Warning: 199 miscellaneous warning
WWW-Authenticate	Indicates the authorization scheme that the client request entity should use	WWW-Authenticate: Basic

For more information, see header field definitions on the W3C website.