Internet Protocols and Applications I

1
Internet Protocols and Applications I
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Some Protocols

• HTTP Communication
• Connectionless Communication
• Stateless Communication

(1) TCP Connection Request
(2) HTTP Request
Server
Client
(3) HTTP Response
(4) TCP Connection Close
3
Some Protocols

• HTTP Message
• Start Line Client Request Information /
  Response Status Information
• Message Header Additional Information for HTTP
  Message such as Date, Program Name, Version,
  Cookie, User Authentication, Cache
• Message Body Contents for Request or Response.
  In case of POST, Input data consists of data
  stream encoded in request message.

4
Some Protocols

• Client Request Message in HTTP
• Request HTTP Command, URI, and HTTP Version,
  Header NameHeader Value, Request Message Body
• HTTP Command GET, HEAD, POST/ OPTIONS, PUT,
  DELETE, LINK, UNLINK, TRACE
• Server Response Message in HTTP
• Response Message HTTP Version, Status Code,
  Code Description, Response Header, Response
  Message Body
• Response Status Code (Reference 100-199),
  (Success 200-299), (Redirection 300-399),
  (Incomplete 400-499), (Server Error 500-599)

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Some Protocols

• HTTP Message Header
• HTTP Header Used for transmitting any kinds of
  information between client and server, Header
  Name Blank Header-value
• General Header Client Request, Server Response,
  Cache setup, Connection, Date, etc
• Client Request Header Client information and
  preferred data type, Accept Character set,
  encoding type, and authorization
• Response Header Server Information, Message
  processing methods for response message. Web
  server information, Cookie setup, authenticate
  information.
• Entity Header HTTP message body information,
  encoding method of message, contents length, MD5
  information, encoding method of contents
  transmission, MIME type

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Some Protocols

• MIME Type
• As HTTP transmission deal with multimedia
  documents, pre-defined method to deal with that
  data by client should be described.
• MIME(Multipurpose Internet Mail Extension) Type
• Client Using Accept Header, Clients can define
  their preferred media type
• Server Describe MIME Type in Content-Type
  Header
• MIME Type form Type/Subtype (ex
  application/x-javascript)
• Standard MIME Type
• Text, Multipart, Message, Application, Image,
  Audio, Video

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CGI Communication

• CGI(Common Gateway Interface)
• Transmit Messages by GET/POST Method
• Characteristics
• Extend Web Server, Dynamic Response, Only Install
  in Server Side
• Overhead, Security, Interactive pages, Cannot
  keep the connection Problems

Process 1
Process 1
Process 1
Web Server
CGI Program
Processes
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Extended CGI

• ASP (Active Server Page) of Microsoft
• Combine HTML, Server side Script, and Server side
  Component
• Written in Jscript, VBScript, and run on IIS
  Server
• Can use COM Component
• Java Servlet and JSP
• Platform Independent, Safe and Effective Thread
  Service, Object Oriented Paradigm
• Easy to interoperate with Legacy Application
• JSP is similar to ASP, and provide HTML script
  language and JavaBeans Component
• Object Web
• CORBA (Common Object Request Broker Architecture)
• EJB (Enterprise JavaBeans)
• DCOM (Distributed Common Object Model)

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Motivations of Servlet and JSP
Slide 9-18, Used the Material by Philippe Rochat

• Faster than CGI (no process creation overhead)
• Java is Internet oriented
• Servlet API
• Security
• Session support
• Code reuse and portability
• JDBC support
• Next step Enterprise Java Beans (EJB)

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How-to

• Very Similar to applet
• Must inherits
• HttpServlet
• Must implements one of
• doGet
• doPost
• doPut
• Receives
• HttpServletRequest
• HttpServletResponse

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Life-Cycle

• Instanciation
• Init()
• Service()
• Done()

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Session

• public void doGet(HttpServletRequest request,
  HttpServletResponse response)
• HttpSession session request.getSession(true)
• session.setAttribute(dataName, dataValue)
• Enumeration e session.getAttributeNames()

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Example

• http//lbdpc15.epfl.ch8080/examples/servlets/sess
  ions.html

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Cookies

• public void doGet(HttpServletRequest request,
  HttpServletResponse response)
• Cookie cookies request.getCookies()
• response.addCookie(c)

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Example

• http//lbdpc15.epfl.ch8080/examples/servlets/cook
  ies.html

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Pros and Cons

• Cons
• HTML embedded in Java source file
• Pros
• Power of Java Platform
• Speed
• Portability across servers and DBs

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More

• At sun
• http//java.sun.com/products/servlet/index.html
• Apache
• http//jakarta.apache.org/tomcat/
• Lbdpc15
• TomCat documentation

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JSP

• Allows HTML embedded tags
• lthtmlgt
• ltjspuseBean id"cart" scope"session"
  class"sessions.DummyCart" /gt
• ltjspsetProperty name"cart" property"" /gt
• lt
• cart.processRequest(request)
• gt
• ltFONT size 5 COLOR"CC0000"gt
• ltbrgt You have the following items in your cart
• ltolgt
• lt
• String items cart.getItems()
• for (int i0 iltitems.length i)
• gt
• ltligt lt itemsi gt
• lt
• gt
• lt/olgt