kmutnb - internet programming 2/7

Web application Architecture and HTTP Protocol

By: Mr. PHUPHA PUNYAPOTASAKUL

(ภู�ผา ปั�ญญาโพธาสกุ�ล)

04/12/23 Free template from www.brainybetty.com 2

World Wide Web

HTMLHTML

HTTPHTTP

TCP/IPTCP/IP

Network LayerNetwork Layer


HTTP Protocol

Hypertext Transfer Protocol (HTTP) is a communications protocol used to transfer or convey information on intranets and the World Wide Web. Its original purpose was to provide a way to publish and retrieve hypertext pages. Development of HTTP was coordinated by the W3C (World Wide Web Consortium) and the IETF (Internet Engineering Task Force), culminating in the publication of a series of RFCs, most notably RFC 2616 (June 1999), which defines HTTP/1.1, the version of HTTP in common use.

http://en.wikipedia.org/wiki/Communications_protocol

http://en.wikipedia.org/wiki/Intranets

http://en.wikipedia.org/wiki/World_Wide_Web

http://en.wikipedia.org/wiki/Hypertext

http://en.wikipedia.org/wiki/World_Wide_Web_Consortium

http://en.wikipedia.org/wiki/Internet_Engineering_Task_Force

http://en.wikipedia.org/wiki/Request_for_Comments

http://tools.ietf.org/html/rfc2616

http://en.wikipedia.org/wiki/June_1999


HTTP Specification

• HTTP 1.1http://tools.ietf.org/html/rfc2616

• HTTP 1.0http://tools.ietf.org/html/rfc1945




HTTP Request/Response

ServerServer

BrowserBrowser HTTP Response

HTTP Request


HTTP Request Methods

• HEAD– Asks for the response identical to the one that would corr

espond to a GET request, but without the response body. This is useful for retrieving meta-information written in response headers, without having to transport the entire content.

• GET– Requests a representation of the specified resource. By fa

r the most common method used on the Web today. Should not be used for operations that cause side-effects (using it for actions in web applications is a common misuse). See 'safe methods' below.

• POST– Submits data to be processed (e.g. from an HTML form

) to the identified resource. The data is included in the body of the request. This may result in the creation of a new resource or the updates of existing resources or both.

http://en.wikipedia.org/wiki/Web_application

http://en.wikipedia.org/wiki/HTML_form


HTTP Request Methods• PUT

– Uploads a representation of the specified resource.• DELETE

– Deletes the specified resource.• TRACE

– Echoes back the received request, so that a client can see what intermediate servers are adding or changing in the request.

• OPTIONS– Returns the HTTP methods that the server supports. This can b

e used to check the functionality of a web server.• CONNECT

– Converts the request connection to a transparent TCP/IP tunnel, usually to facilitate SSL-encrypted communication (HTTPS) through an unencrypted HTTP proxy.[1]

http://en.wikipedia.org/wiki/Tunneling_protocol



http://en.wikipedia.org/wiki/Transport_Layer_Security

http://en.wikipedia.org/wiki/Proxy_server

http://en.wikipedia.org/wiki/HTTP#_note-0




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

HTTP Response HTTP/1.1 200 OK Date: Mon, 23 May 2005 22:38:34 GMT Server: Apache/1.3.27 (Unix) (Red-Hat/Linux) Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT Accept-Ranges: bytes Content-Length: 438 Connection: close Content-Type: text/html; charset=UTF-8

<HTML> <HEAD> <TITLE>Title</TITLE>….

http://www.example.com/


HTML


HTML Example<html><head><title>Title</title><meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<link href="../style/framework.css" rel="stylesheet" type="text/css"><script language="JavaScript" src="../script/framework/config.js"></script></head>

<body leftmargin="0" topmargin="0" marginwidth="0" marginheight="0">….…..….</body></html>


HTML Specification

• Referencehttp://www.w3.org/TR/html4/

• Maintain by

• Support Historyhttp://www.eskimo.com/~bloo/indexdot/html/supportkey/a.htm

http://www.w3.org/TR/html4/












http://www.eskimo.com/~bloo/indexdot/html/supportkey/a.htm




How does it work?

BrowserBrowser

HTTP Request

TCP/IP Packet

Network


How does it work?

ServerServer

HTTP Request

TCP/IP Packet

Network

HTML Output

HTTP Response

TCP/IP Packet


How does it work?

BrowserBrowser

Network

HTML Output

HTTP Response

TCP/IP Packet


Question

• If HTTP message is larger than TCP/IP packet’s max length, what will happen?

• Is it possible to have more than one web site in the same server? How does it work?

• How can we know the server’s IP address


TCP/IP

• Each TCP/IP connection– Source IP– Source Port– Destination IP– Destination Port

• Reliable transmission

• Establish connection before transmit

• More overhead than UDP


Virtual Host

• Multi domain name in one server

• Each domain name have their own content, files, resource and etc. separately

• Domain name come from HTTP Request message

• Where IP come from?


HTTP Persistent Connection

• Send multi HTTP Request in one connection

• Why?– Reduce overhead– Get response faster


HTTP Session State

• HTTP is a stateless protocol

• Web server implementation much easier and much more effective

• Dynamic content?

• Control session on application level


More detail about HTTP

• HTTP Header specificationhttp://en.wikipedia.org/wiki/List_of_HTTP_headers

• HTTP Status codehttp://en.wikipedia.org/wiki/List_of_HTTP_status_codes

• HTTP Compression– Reduce bandwidth– Use Content-Encoding

http://en.wikipedia.org/wiki/List_of_HTTP_headers











http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

http://en.wikipedia.org/wiki/List_of_HTTP_status_codes


Server concept

ApplicationApplicationHTTP Request

HTTP Response


Server concept

Web ServerWeb Server

HTTP Request

Request parameter Server PageServer Page

Server PageServer PageServer PageServer Page

Server PageServer Page

Use URI pattern to select which page to run..

HTML Output

+

Response parameter

HTTP Response


E.g. JSP


Server PageServer Page

Request Object

ResponseObject


URL

• Uniform Resource Locators (URLs) are strings that specify how to access network resources, such as HTML documents. They are part of the more general class of Universal Resource Identifiers (URIs). The most important use of URLs is in HTML documents to identify the targets of hyperlinks. When using a Web browser such as Netscape, every highlighted region has a URL associated with it, which is accessed when the link is activated by a mouse click. Relative URLs specify only a portion of the full URL - the missing information is inferred though the context of the source document.


Secure Socket Layer

• Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers.

• URL pattern – https://• For HTTP, normally use port 443• More detail later

http://en.wikipedia.org/wiki/Cryptographic_protocol

http://en.wikipedia.org/wiki/Security

http://en.wikipedia.org/wiki/Internet

http://en.wikipedia.org/wiki/Web_browsing

http://en.wikipedia.org/wiki/Electronic_mail



http://en.wikipedia.org/wiki/Internet_fax

http://en.wikipedia.org/wiki/Instant_messaging


Web Cookies

• HTTP cookies, sometimes known as web cookies or just cookies, are parcels of text sent by a server to a web browser and then sent back unchanged by the browser each time it accesses that server. HTTP cookies are used for authenticating, tracking, and maintaining specific information about users, such as site preferences and the contents of their electronic shopping carts. The term "cookie" is derived from "magic cookie," a well-known concept in unix computing which inspired both the idea and the name of HTTP cookies.


Web Cookies


Session

• Normally manage by web server

• Use cookie to help keeping session id or session identifier

• Session timeout, unused data will be cleared from memory


Session

BrowserBrowser


Session ID

Cookie

Session DataSession

DataSession DataSession

Data

BrowserBrowserSession

ID

Cookie


Question

• If we close browser, will the cookie disappear?

• Can we change value in cookie manually?

• How to open web site in a new session– Open new browser window?

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