Web Programming and Internet Technologies
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This document discusses web programming and internet technologies. It distinguishes between the Internet, which is a worldwide collection of connected computers and devices, and the World Wide Web, which is a software system for accessing and sharing information over the Internet. The document explains how the client-server model and protocols like HTTP allow web browsers and servers to communicate and share web pages and other resources identified by URLs.
Web Programming and Internet Technologies
- 2. OBJECTIVES • Distinguish between the Internet and the World Wide Web • Explain client-server architecture • Discuss how web browsers and servers communicate CPTR304: Internet Authoring 1/13/2014 2
- 3. WHAT IS THE INTERNET? • World-wide collection of computers and other devices connected via communications media • Started in the 1960s • Initial development under the auspices of the ARPA (Advanced Research Projects Agency) • Other networks developed by late 1970s, early 1980s CPTR304: Internet Authoring 1/13/2014 3
- 4. CPTR304: Internet Authoring Visualization of the various routes through parts of the Internet. 1/13/2014 4
- 5. WHAT IS THE WORLD WIDE WEB (WWW)? • “software infrastructure” consisting of various communications standards for gaining access to, and exchanging information over, the internet • Development started in the late 1980s by Sir Tim Berners-Lee and others at CERN (European Organization for Nuclear Research) • The idea was to make scientific documents available over the Internet • HTML was developed for the purpose of describing the structure of documents • Browsers, with simple text-based interfaces were used to retrieve and display the documents (Lynx) • Mosaic, the first widely used GUI browser CPTR304: Internet Authoring 1/13/2014 5
- 6. CLIENT-SERVER ARCHITECTURE CPTR304: Internet Authoring 1/13/2014 6
- 7. HOW WEB BROWSERS AND WEB SERVERS COMMUNICATE 1.Web Protocols and Layered Communication Architectures 2.Web Addresses and Address Resolution via DNS 3.URLs, URNs, and URIs CPTR304: Internet Authoring 1/13/2014 7
- 8. 1. WEB PROTOCOLS AND LAYERED COMMUNICATION ARCHITECTURES • Communication protocol: an agreement between two or more parties about what rules will be followed when communication takes place. • Web protocol: agreed-upon set of rules and date formats to be used when two or more computers or other devices, or application programs running on those machines, wish to communicate across the Internet. CPTR304: Internet Authoring 1/13/2014 8
- 9. COMMON WEB PROTOCOLS • TCP/IP • UDP • HTTP/HTTPS • FTP • TELNET and SSH CPTR304: Internet Authoring 1/13/2014 9
- 10. LAYERED COMMUNICATION ARCHITECTURE CPTR304: Internet Authoring 1/13/2014 10
- 11. 2. WEB ADDRESSES AND ADDRESS RESOLUTION VIA DNS • IP Address: has the form a.b.c.d, where each of the values is a positive integer in the range 0…255 (32-bit address/~4 billion addresses) • E.g. 74.125.229.243 • FQDN: human-readable version of an IP address • E.g www.google.com • Host Machines and domains • Domain Name System and Domain Name Servers CPTR304: Internet Authoring 1/13/2014 11
- 12. The logical hierarchy of the Domain Name Service (DNS) CPTR304: Internet Authoring 1/13/2014 12
- 13. 3. URLS, URNS, AND URIS • Uniform Resource Locator (URL): a standard way of referring to the location of a web document/resource • scheme: address_of_resource • http://cis.ncu.edu.jm • Uniform Resource Name (URN): has the same form as a URL but may not identify an actual location on the Internet. • urn:isan:0000-0000-9E59-0000-O-0000-0000-2 • The 2002 film Spider-Man, identified by its audiovisual number. • Uniform Resource Identifier (URI): a string of characters used to identify a name of a web resource. URIs can be classified as locators (URLs), as names (URNs), or as both. CPTR304: Internet Authoring 1/13/2014 13
Editor's Notes
- #6: Centre europeen pour la recherché nucleaire
- #7: Typically, client-machine first sends a request to a server-machineServer then honors the request by returning to the user whatever was requested, or returns an error that indicates why the request couldn’t be honored
- #14: A uniform resource name (URN) functions like a person's name, while a uniform resource locator (URL) resembles that person's street address. In other words: the URN defines an item's identity, while the URL provides a method for finding it.The ISBN system for uniquely identifying books provides a typical example of the use of URNs. ISBN 0-486-27557-4 (urn:isbn:0-486-27557-4) cites unambiguously a specific edition of Shakespeare's play Romeo and Juliet. To gain access to this object and read the book, one needs its location: a URL address. A typical URL for this book on a Unix-like operating system would be a file path such asfile:///home/username/books/RomeoAndJuliet.pdf, identifying the electronic book library saved on a local disk drive. So URNs and URLs have complementary purposes.URLs and URNs[edit]A URL is a URI that, in addition to identifying a web resource, specifies the means of acting upon or obtaining the representation: providing both the primary access mechanism, and the network "location". For example, the URL http://example.org/wiki/Main_Page refers to a resource identified as/wiki/Main_Page whose representation, in the form of HTML and related code, is obtainable via HyperText Transfer Protocol (http://) from a network host whose domain name is example.org.