Web HTTP
HTTP uses the client-server model. An HTTP client opens a connection and sends a request message to an HTTP server, the server then returns a response message, usually containing the resource that was requested.
HTTP request message consists of the followings in the given order:
- Request line: GET /xyz.html HTTP/1.1
- Host name: Host www.example.com
- Optional headers: Key value pair, separated by a colon (:) .
- An empty line.
- Optional Body.
Example
GET / HTTP/1.1 Host: www.example.com Connection: keep-alive Cache-Control: max-age=0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,.. Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/... Safari/537.36 Accept-Encoding: gzip, deflate, sdch Accept-Language: en-US,en;q=0.8 If-None-Match: "359670651+gzip" If-Modified-Since: Fri, 09 Aug 2013 23:54:35 GMT
An HTTP response message consists of the followings parts:
- Status line: HTTP/1.1 OK
- Headers: Key value pair.
- An empty line.
- Body.
Example
HTTP/1.1 304 Not Modified Cache-Control: max-age=604800 Date: Mon, 01 Feb 2016 08:44:57 GMT Etag: "359670651+gzip" Expires: Mon, 08 Feb 2016 08:44:57 GMT Last-Modified: Fri, 09 Aug 2013 23:54:35 GMT Server: ECS (ftw/FBE4) Vary: Accept-Encoding X-Cache: HIT x-ec-custom-error: 1
<html> <head> <title>Example Domain</title>
<meta charset="utf-8" /> <meta http-equiv="Content-type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1" /> <style type="text/css"> ..... <body> ..... ..... </body> </html>
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