The HTTP headers,
The hypertext transfer protocol (HTTP (HyperTextTransferProtocol), the common protocol web transmission at present. HTTP protocol uses a request/response model, the browser or other clients make a request, the server gives a response. In terms of the whole network resource transmission, message-header and message-body are included. The message-header, or HTTP header message, is first passed. HTTP Header Messages are usually divided into four parts: General Header, Request Header, Response Header, and Entity Header. But this division in terms of understanding, the sensory boundaries are not very clear. According to the organization form of HTTP header content in Wikipedia, it can be roughly divided into Request and Response.
Part Requests
| Header | explain | The sample |
|---|---|---|
| Accept | Specifies the type of content that the client can receive | Accept: text/plain, text/html |
| Accept-Charset | A set of character encodings acceptable to the browser. | Accept-Charset: iso-8859-5 |
| Accept-Encoding | Specifies the type of web server content compression encoding that the browser can support. | Accept-Encoding: compress, gzip |
| Accept-Language | Browser acceptable language | Accept-Language: en,zh |
| Accept-Ranges | You can request one or more subscope fields of a web page entity | Accept-Ranges: bytes |
| Authorization | HTTP authorization certificate | Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== |
| Cache-Control | Specify the caching mechanism that requests and responses follow | Cache-Control: no-cache |
| Connection | Indicates whether a persistent connection is required. (HTTP 1.1 makes 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 | The content length of the request | Content-Length: 348 |
| Content-Type | MIME information that corresponds to the entity being requested | Content-Type: application/x-www-form-urlencoded |
| Date | The date and time the request was sent | Date: Tue, 15 Nov 2010 08:12:31 GMT |
| Expect | The specific server behavior requested | Expect: 100-continue |
| From | Email address of the user who made the request | From: [email protected] |
| Host | Specifies the domain name and port number of the requested server | Host: www.zcmhi.com |
| If-Match | This is valid only if the request content matches the entity | If – the Match: “737060 cd8c284d8af7ad3082f209582d” |
| If-Modified-Since | If the part of the request is modified after the specified time, the request succeeds; if it is not modified, the 304 code is returned | If-Modified-Since: Sat, 29 Oct 2010 19:43:31 GMT |
| If-None-Match | If the content has not changed, the 304 code is returned with the Etag sent by the server. The Etag is compared with the Etag returned by the server to determine whether it has changed | If None – Match: “737060 cd8c284d8af7ad3082f209582d” |
| If-Range | If the entity has not changed, the server sends the missing part of the client, otherwise sends the whole entity. The parameter is also Etag | If – Range: “737060 cd8c284d8af7ad3082f209582d” |
| If-Unmodified-Since | The request succeeds only if the entity has not been modified after the specified time | If-Unmodified-Since: Sat, 29 Oct 2010 19:43:31 GMT |
| Max-Forwards | Limit the amount of time messages can be sent through proxies and gateways | Max-Forwards: 10 |
| Pragma | Used to contain implementation-specific instructions | Pragma: no-cache |
| Proxy-Authorization | Certificate of authorization to connect to the agent | Proxy-Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== |
| Range | Only a portion of the entity is requested, specifying scope | Range: bytes=500-999 |
| Referer | The address of the previous web page, followed by the current requested web page, is the incoming path | Referer: www.zcmhi.com/archives/71… |
| TE | The client is willing to accept the transmission code and notifies the server to accept the end plus header message | TE: trailers,deflate; Q = 0.5 |
| Upgrade | Specify some transport protocol to the server for the server to convert (if supported) | Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/ X11 |
| User-Agent | User-agent contains the information about the User that sends the request | The user-agent: Mozilla / 5.0 (Linux; X11) |
| Via | Notification intermediate gateway or proxy server address, communication protocol | Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1) |
| Warning | Warning information about message entities | Warn: 199 Miscellaneous warning |
Responses of
| Header | explain | The sample |
|---|---|---|
| Accept-Ranges | Indicates whether the server supports scoped requests and what type of segmented requests | Accept-Ranges: bytes |
| Age | Estimated time from the original server to proxy cache formation (in seconds, non-negative) | Age: 12 |
| Allow | A valid request for a network resource. If not allowed, 405 is returned | Allow: GET, HEAD |
| Cache-Control | Tell all caching mechanisms whether they can cache and what type | Cache-Control: no-cache |
| Content-Encoding | The type of returned 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 | Request an alternate address for alternate resources | Content-Location: /index.htm |
| Content-MD5 | Returns the MD5 check value 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 when the original server message was sent | Date: Tue, 15 Nov 2010 08:12:31 GMT |
| ETag | The current value of the entity label of the request variable | ETag: “737060 cd8c284d8af7ad3082f209582d” |
| Expires | The expiration date and time of the response | 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 the location of the non-requested URL to complete the request or to identify a new resource | Location: www.zcmhi.com/archives/94… |
| Pragma | This includes implementing specific instructions that can be applied to any recipient on the response chain | Pragma: no-cache |
| Proxy-Authenticate | It indicates the authentication scheme and the parameters that can be applied to the URL of the broker | Proxy-Authenticate: Basic |
| refresh | Applied to redirects or a new resource is created, redirects after 5 seconds (proposed by Netscape and supported by most browsers) | Refresh: 5; url=www.zcmhi.com/archives/94… |
| Retry-After | If the entity is temporarily unavailable, notify the client to try again after the specified time | Retry-After: 120 |
| Server | Name of the Web server software | Server: Apache / 1.3.27 (Unix) (Red Hat/Linux) |
| Set-Cookie | Set the Http cookies | Set-Cookie: UserID=JohnDoe; Max-Age=3600; Version=1 |
| Trailer | Indicates that the header field exists at the end of the block transfer code | Trailer: Max-Forwards |
| Transfer-Encoding | File transfer coding | Transfer-Encoding:chunked |
| vary | Tell the downstream proxy whether to use a cached 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 | Alerts entities to possible problems | Warning: 199 Miscellaneous warning |
| WWW-Authenticate | Indicates the authorization scheme that the client requesting entity should use | WWW-Authenticate: Basic |