HyperText Transfer Protocol..

HTTP ( is the protocol used to transfer Web pages through the Internet )

The HyperText Transfer Protocol (HTTP) defines how clients and servers communicate. HTTP is generic object-oriented, stateless protocol to transmit information between servers and clients (Bernets-Lee 1992). HTTP/0.9 was used during the early development of the Web. HTTP/1.0 which was released in 1995 as informational RFC 1945, reflected common usage of the protocol (Berners-Lee et al., 1996). The most recent release. HTTP/1.1 provides more functionality and support for allowing multiple transactions to occur between client and server over the same request.

HTTP is based on a request-response paradigm. An HTTP transaction consists of the following stages.

*) Connection – the client establishes a connection with the Web server.
*) Request – the client sends a request message to the Web server.
*) Response – the Web server sends a response to the client.
*) Close – the connection is closed by Web server.

HTTP is currently a stateless protocol – the server retains no information between requests. Thus a Web server has no memory of previous requests, this means that the information a user enters on one page is not automatically available on the next page requested, unless the Web server takes steps to make that happen, in which case the server must somehow identify which requests, out of the thousands of requests it receives, come from the same user. For most applications, this stateless property of HTTP is a benefit that permits clients and servers to be written with simple logic and run ‘lean’with no extra memory or disk space taken up with information from old requests. Unfortunately the stateless property of HTTP makes it difficult to support the concept of the session that as essential to basic DBMS transactions. Various schemes have been proposed to compensate for the stateless nature of HTTP, such as returning Web pages with hidden fields containing transaction identifiers, and using Web page forms where all the information is entered locally and then submitted as a single transaction. All these schemes are limited in the types of application they support and require special extensions to the Web servers.

HTTP request..

An HTTP request consists of a header indicating the type of request, the name of a resource, the HTTP version, followed by an optional body. The header is separated from the body by a blank line. The main HTTP request types are :

*) GET (This is one of the most common types of request, which retrieves (gets) the resource the user has requested.)
*) POST (Another common type of request, which transfers (posts) data to the specified resource. Usually the data sent comes from an HTML from that the user had filled in, and the server may use this data to search the internet or query a database.)
*) HEAD ( Similar to GET but forces the server to return only un HTTP header instead of response data.)
*) PUT (HTTP/1.1) Uploads the resource to the server.
*) DELETE (HTTP/1.1) Deletes the resource from the server.
*) OPTIONS (HTTP/1.1) Requests the server’s configuration options.


HTTP response..

An HTTP response has a header containing the HTTP version, the status of the response, and header information to control the response behavior, as well as any requested data in a response body. Again, the header is separated from the body by the blank line.