VIT, CHENNAI

SEMINAR TOPIC

“HTTP”

Presented by: Course Faculty:Akshay Dhole(13MMT1013) Prof. Nitya Darisini

Introduction:-Internet is a distributed- client/server information system.-Many applications such as web browsing/surfing, email, file transfer, audio and video streaming etc.

From which http is the most popular application protocol.

HTTP uses the TCP-IP services port 80

HTTP:-The Hypertext Transfer Protocol (HTTP) is a protocol-Mainly used to access data on the World Wide Web. -HTTP functions as a combination of FTP and SMTP.

HTTP is an asymmetric request-response client-server protocol.

An HTTP client sends a request message to an HTTP server. The server, in turn, returns a response message.

HTTP is a stateless protocol. In other words, the current request does not know what has been done in the previous requests.

HTTP Conversation:

Browser:

Whenever you issue a URL from your browser to get a web resource using HTTP, e.g. http://www.test101.com/index.html, the browser turns the URL into a request message and sends it to the HTTP server.

The HTTP server interprets the request message, and returns you an appropriate response message, which is either the resource you requested or an error message.

URL:A URL (Uniform Resource Locator) is used to uniquely

identify a resource over the web.

There are 4 parts in a URL:1. Protocol: The application-level protocol used by the

client and server, e.g., HTTP, FTP, and telnet.2. Hostname: The DNS domain

name (e.g., www.test101.com) or IP address (e.g., 192.128.1.2) of the server.

3.Port: The TCP port number that the server is listening for incoming requests from the clients.

4.Path-and-file-name: The name and location of the requested resource, under the server document base directory.

HTTP Specifications:The HTTP specification is maintained by 

W3C (World-wide Web Consortium) and available at http://www.w3.org/standards/techs/http.

There are currently two versions of HTTP, namely, HTTP/1.0 and HTTP/1.1.  The original version, HTTP/0.9 (1991), written by Tim Berners-Lee, is a simple protocol for transferring raw data across the Internet.

HTTP/1.0 (1996) (defined in RFC 1945), improved the protocol by allowing MIME-like messages.

HTTP/1.0 does not address the issues of proxies, caching, persistent connection, virtual hosts, and range download. These features were provided in HTTP/1.1 (1999) (defined in RFC 2616).

HTTP ProtocolWhenever you enter a URL in the address box of the browser, the

browser translates the URL into a request message according to the specified protocol; and sends the request message to the server

When this request message reaches the server, the server can take either one of these actions:

The server interprets the request received, maps the request into a file under the server's document directory, and returns the file requested to the client.

The server interprets the request received, maps the request into a program kept in the server, executes the program, and returns the output of the program to the client.

The request cannot be satisfied, the server returns an error message.

HTTP TransactionFollowing fig. illustrates the HTTP transaction between the client

and server.

Message:A request message consists of a request

line, a header, and sometimes a body. A response message consists of a status line, a header, and sometimes a body.

Request and status linesThe first line in a request message is called a request line. The

first line in the response message is called the status line.

HTTP request methods:GET:• Request a document from the server

Head:• Request the information of the document but not the document

POST:• Sends information from client to server

Put:• Sends document from server to client

Trace :• Echoes the incoming request

Connect:• Reserved

Option:• Inquires about available options.

Status codesThis field is used in the response message. The status code field is similar

to those in the FTP and the SMTP protocols. It consists of three digits.

The codes in the 100 range- informational,

The codes in the 200 range- successful request.

The codes in the 300 range- redirect the client to another URL

the codes in the 400 range- an error at the client site.

the codes in the 500 range - an error at the server site.

Headers:• The header exchanges additional information between the

client and the server. For example, the client can request that the document be sent in a special format, or the server can send extra information about the document.

• A header line belongs to one of four categories: general header, request header, response header, and entity header. A request message can contain only general, request, and entity headers.• A response message, on the other hand, can

contain only general, response, and entity headers.

General headers• The general header gives general information about the

message and can be present in both a request and a response.

Request header

• The request header can be present only in a request message. It specifies the client's configuration and the client's preferred document format.

Response headers• The response header can be present only in a response

message. It specifies the server's configuration and special information about the request.

Entity headers:

• The entity header gives information about the body of the document. Although it is mostly present in response messages, some request messages, such as POST or PUT methods, that contain a body also use this type of header.

Thank You