HTTP

Hypertext Transfer Protocol (HTTP) is a method used to transfer or convey information on the World Wide Web. It is a patented open internet protocol whose original purpose was to provide a way to publish and receive HTML pages. HTTP is a request/response protocol between clients and servers. The originating client, such as a web browser, spider, or other end-user tool, is referred to as the user agent. The destination server, which stores or creates resources such as HTML files and images, is called the origin server.

HTTP Conversation
Below is a sample of part of an HTTP conversation:

Client Request
GET /index.html HTTP/1.1 Host: www.example.com

Server Response
HTTP/1.1 200 OK Date: Thu, 17 Aug 2006 22:38:34 GMT Server: Apache/1.3.33 (Unix) (Debian/Linux) Last-Modified: Tue, 15 Aug 2006 23:11:55 GMT Etag: "3f80f-1b6-3e1cb03b" Accept-Ranges: bytes Content-Length: 438 Connection: close Content-Type: text/html; charset=UTF-8