HTTP is the most popular application protocol on the internet. It uses the client-server model where an HTTP client sends a request to an HTTP server using a request method like GET or POST. The server then returns a response with a status code and can include a message body. A URL identifies a web resource and includes the protocol, hostname, port, and path. HTTP specifications are maintained by the W3C and the current versions are HTTP/1.0 and HTTP/1.1. The HTTP request and response include a start line, headers, and optional body. Common status codes indicate success, redirection, or client/server errors.

1. VIT, CHENNAI
SEMINAR TOPIC
“HTTP”
Presented by: Course Faculty:
Akshay Dhole(13MMT1013) Prof. Nitya Darisini

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

3.  From which http is the most
popular application protocol.
HTTP uses the TCP-IP services
port 80

4. 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.

5. HTTP Conversation:

6. 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.

8. 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.

9. 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).

10. HTTP Protocol
Whenever 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.

11. HTTP Transaction
Following fig. illustrates the HTTP transaction between the client
and server.

12. 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.

13. Request and status lines
The first line in a request message is called a request line. The
first line in the response message is called the status line.

14. 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.

15. Status codes
This 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.

18. 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.

19. • 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.

20. General headers
• The general header gives general information about the
message and can be present in both a request and a response.

21. 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.

23. 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.

24. 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.

26. Thank You