The Hypertext Transfer Protocol (HTTP) is an application-level protocol that lets you exchange different types of media over the Worldwide Web. Basically, it is the language that Web clients and servers use to communicate. Released in 1990, the original version of HTTP (HTTP/0.9) was a very simple protocol for raw data transfer across the Internet. The current version (HTTP/1.1) has been greatly improved to make Web client/server connections more reliable, efficient, and secure. With the current version of HTTP, servers can transmit multiple objects such as text and graphics, through a single TCP connection using longer packets. It also allows a client to save Web pages through caching and to compare saved pages with requested pages. If the two are identical, the Web browser will use the Cached copy of the page to save bandwidth and time.
The HTTP protocol is a request/response protocol. When you enter an address of a web site into a web browser’s address field, the browser builds an HTTP request and sends it out to the IP address indicated by the URL. It then returns the Web server’s information to you in Hypertext Markup Language (HTML). Every Web server machine has an HTTP daemon. A daemon is a program that is designed to wait for HTTP requests and handle them when they arrive. The HTTP daemon in the destination server machine receives the request and, after any necessary processing, sends back a response with the requested information. HTTP uses a formatted string called a URI (Uniform Resource Identifier) to identify a resource. A URI is a combination of a URL (Uniform Resource Locator) and a URN (Uniform Resource Name). URIs are also known as WWW addresses and Universal Document Identifiers.
Hypertext Transfer Protocol is used for communication between a browser and a Web server. It has a set of rules for exchanging files on the Web. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred. The protocol is called, connectionless because, once the single request has been satisfied, the connection is dropped. The HTTP protocol is based on a request/response paradigm. The communication generally takes place over a TCP/IP connection on the Internet. The default port is 80, but other ports can be used. This does not preclude the HTTP/1.0 protocol from being implemented on top of any other protocol on the Internet, so long as reliability can be guaranteed.