1. Free Powerpoint Templates Page 1 Free Powerpoint Templates CHAPTER 1 LAB 1.1 Web Server

2. Free Powerpoint Templates Page 2 CONTENTS Client/Server Basics Electronic Publishing HTTP Overview Other Web-Related Servers

3. Free Powerpoint Templates Page 3 CLIENTS AND SERVER describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfills the request CLIENT Client- a piece of hardware/software used to communicate with a date provider (server) Only one user uses a specific client at a time SERVER Physical computer refer to the actual server software/daemon running on the machine Daemon- a program that offers services to other programs, usually over a network.

4. Free Powerpoint Templates Page 4 World Wide Web (WWW) Uses this client/server model to allow millions of users to access Web sites all over the world WEB SERVER: Is a specific type of server that knows how to communicate with clients using the HyperText Transfer Protocol (HTTP) –A protocol- a standard set of rules that allow a client an server to communicate. –Allows clients to request documents and servers to respond with those documents.

5. Free Powerpoint Templates Page 5 Video – Word Wide Web

6. Free Powerpoint Templates Page 6 TCP/IP Network Connections/Ports Transmission Control Protocol/ Internet Protocol (TCP/IP) Allows different types of computers to communicate at a low level ;it is up to applications, however to determine how client/server talk Uses IP Addresses to communicate between computers The destination computer may have many different services running on it, so to specify which service we want to communicate with, we must use a PORT NUMBER

7. Free Powerpoint Templates Page 7 Server and Browser The main goal of any Web server – to provide documents to clients To retrieve and display information from a Web Server by using HTTP A browser allows any user to access a server easily.

8. Free Powerpoint Templates Page 8 Browser Plug-Ins Extends browser capability More than just HTML –RealPlayer - live audio and video –Shockwave - animations –Acrobat Reader - view PDF files

9. Free Powerpoint Templates Page 9 Free Powerpoint Templates LAB 1.2 Electronic Publishing

10. Free Powerpoint Templates Page 10 Strength of the Web -The support of hypertext documents -Contains hyperlinks that allow the reader to jump easily from one document to another or to move around the current document -Allow users to follow a specific thread or view quickly documents on related topics -Links can be images, sounds, animations, and even videos- called hypermedia

11. Free Powerpoint Templates Page 11 Two File Types In the Web-publishing realm, two types of files: ASCII text files –Can be HTML –Plain text or some other simple format Binary Files –Images –Sounds –Programs

12. Free Powerpoint Templates Page 12 Image File Type- GIF Graphics Interchange Format (GIF) –256 colours –Lossless compression –Transparency –Can be animated –Good for illustrations –Proprietary (patent)

13. Free Powerpoint Templates Page 13 Image File Types (PNG & JPEG) Portable Network Graphics (PNG) –As GIF except: More colours No animation Not proprietary Joint Photographic Experts Groups (JPEG) Millions of colours Lossy compression Good for photographs

14. Free Powerpoint Templates Page 14 Audio File Types WAV –Windows AIFF –Macintosh AU –Unix Modern browsers support all these and more

15. Free Powerpoint Templates Page 15 MIME Types Multipurpose Internet Mail Extensions (MIME) –A type of a file before it sends it to the browser –The browser can use the MIME type to determine how it should display the document. –Both server/client must have a simple MIME types database. –There are 7 different media types in use: Application = application/excel Audio = audio/midi Image = image/jpeg Message = message/news Multipart = multipart/digest Text = text/html Video = video/mpeg

16. Free Powerpoint Templates Page 16 Sample – Fantastic Website

17. Free Powerpoint Templates Page 17 Free Powerpoint Templates LAB 1.3 HTTP Overview

18. Free Powerpoint Templates Page 18 HTTP TRANSACTIONS HTTP –Protocol that allows Web browsers to talk to servers and exchange information –Provides a standard way of communicating between browsers and Web servers –Expects the client to initiate a request and the server to respond –Each request has THREE parts: the request or status line, the header fields, and the entity body

19. Free Powerpoint Templates Page 19 HTTP REQUEST REQUEST LINE HEADER SECTION ENTITY BODY Request method, Resource location, Protocol Version Information about request, client Data to be passed to the server

20. Free Powerpoint Templates Page 20 HTTP Response The server then responds to the request in a similar fashion STATUS LINE HEADER SECTION ENTITY BODY Status code, reason phrase, protocol version Information about server, response Requested resource-often HTML

21. Free Powerpoint Templates Page 21 REQUEST METHOD The request line of a client request contains an HTTP command called REQUEST METHOD GET –Used to retrieve information from the server –Can be used to pass data to the server HEAD –Identical to the GET method except that the server does not return a document –It returns the header section for the request –Use to verify the existence of a resource POST –Allows the server to receive data from the client –Typically used to send the data in HTML forms to the server for processing. –Passes data to the server in the entity body of the request

22. Free Powerpoint Templates Page 22 OTHER METHODS PUT –Used for publishing documents to the Web server from a client DELETE –Is used to remove a document from a Web server.

23. Free Powerpoint Templates Page 23 SERVER RESPONSES After an HTTP server receives a request It attempts to process the request The server response like the client request: –The status line –Header fields –The entity body

24. Free Powerpoint Templates Page 24 Status Line The status line contains three things –the protocol version –The status code A three-digit integer result code defined by the HTTP specification The first digit of the status code represent the category of the response ( go next slide) –A description phrase

25. Free Powerpoint Templates Page 25 Five categories of the Status Code Informational –The request was received and is being processed Success –The client request was successful Redirection –the client request was not performed; further action must be taken by the client Client Error –The client’s request was incomplete or incorrect and cannot be fulfilled Server Error –The request was not fulfilled, due to a server problem

26. Free Powerpoint Templates Page 26 Most common Response Code 100 Continue –The initial part of the request has been received and the client should continue 200 OK –This is probably the most common response –It means that the client’s request was successful and the server’s response contains the resource requested. 400 BAD Request –The server could not understand the request

27. Free Powerpoint Templates Page 27 HTTP Headers Is used to transfer information between the client and server A header has a name and a value associated with it Examples of HTTP headers( 2 categories): –CLIENT REQUEST HEADERS –SERVER RESPONSE HEADERS

28. Free Powerpoint Templates Page 28 CLIENT REQUEST HEADERS AcceptUsed to specify which media types the client prefers to accept CookieContains cookie information for the URL requested If-Modified-SinceUsed to do a conditional GET request. The server will return the document only if it has been modified since the date specified RefererAllows the client to specify the URL of the page from which the currently requested URL was obtained User-AgentContains information about the client program originating the request. Used to identify the browser software.

29. Free Powerpoint Templates Page 29 SERVER RESPONSE HEADER ServerContains information about the server software handling the request Set-cookieAllows the server to set a cookie on the client browser for the given URL or domain

30. Free Powerpoint Templates Page 30 ENTITY HEADERS Content-LengthSpecifies the sixe of the data transferred in the entity body Content-TypeSpecifies the MIME type of the data returned in the entity body ExpiresSpecifies the time/date after which the response is considered outdated. Last-ModifiedSpecifies the date and time the document was last modified

31. Free Powerpoint Templates Page 31 Free Powerpoint Templates LAB 1.4 OTHER WEB-RELATED SERVERS

32. Free Powerpoint Templates Page 32 PROXY SERVER Intermediary server that goes between a client and the destination- a middleman Three main uses: –Security Firewall Allowing only HTTP traffic through and rejecting other protocols. –Content filtering Filter data, restricting access to certain sites or analyzing content for questionable material –Caching Help improve performance by storing frequently accessed documents locally.

33. Free Powerpoint Templates Page 33 STREAMING AUDIO AND VIDEO For a browser to play an audio/video file, it must first download the entire file.

34. Free Powerpoint Templates Page 34 FILE TRANSFER PROTOCOL File Transfer Protocol (FTP) –Used to transfer files between computers on a network. –A host with a Web server running on it may also set up an FTP server FTP DAEMON -A program that runs on the server and allows clients to connect -Provides a means of authentication so that only authorizes users can transfer files to and from the server

35. Free Powerpoint Templates Page 35 DATABASES Stores details in fields on a server so that they can later called.

36. Free Powerpoint Templates Page 36 SSL Secure Sockets Layer A protocol developed by Netscape for transmitting private documents via the Internet. SSL uses a cryptographic system that uses two keys to encrypt data − a public key known to everyone and - a private or secret key known only to the recipient of the message.

37. Free Powerpoint Templates Page 37 THE END