Internet Programming-I

1. Internet Programming-I

2. Introduction :Internet Programming • Web service is a kind of client / server process • Need interaction between client and server • Programming for providing Web service can also be divided into • Client-side programming: to define the operation to be performed on the client’s machine • Server-side programming: to define the operation to be performed on the server

3. Internet Database Web Server Web Client • Server-side Programming • Skills that are often required: • PHP • ASP • Perl • Java Servlet, … • Client-side Programming • Skills that are often required: • HTML • XHTML • Javascript • Java • Dreamweaver • SMIL, XML …

4. Introduction • What is Internet programming? • The client server communication established with the help of scripting and markup languages following all the communication protocols and transmission protocols can be defined as Internet programming. • An Internet application is a client-server application that uses standard Internet protocols for connecting the client to the server.

5. Contd.(Introduction ) • Internet programming includes broad variety of technologies spanning such diverse areas such as: • protocols for communication networks, • interfacing to databases, • programming of graphical user interfaces, or • Structuring information.

6. World Wide Web • A system of Internetservers that support specially formatteddocuments. • The world wide web is a system of Internet servers that supports hypertext and multimedia to access several Internet protocols on a single interface. • The World Wide Web is often abbreviated as the web or www. • The documents are formatted in a markup language called HTML (HyperText Markup Language) that supports links to other documents, as well as graphics, audio, and video files. • This means you can jump from one document to another simply by clicking on hot spots.

7. Contd. • There are several applications called Web browsers that make it easy to access the World Wide Web; • Two of the most popular being Firefox and Microsoft's Internet Explorer. • World Wide Web is not synonymous with the Internet.

8. What is a protocol? • In diplomatic circles, a protocol is the set of rules governing a conversation between people • We have seen that the client and server carry on a machine-to-machine conversation • A network protocol is the set of rules governing a conversation between a client and a server • There are many protocols, HTTP is just one

9. Protocols of the Web • The surface simplicity of the Web comes from the fact that many individual protocols can be contained within a single Web site. • internet protocols are sets of rules that allow for inter machine communication on the Internet. • These are a few of the protocols you can experience on the Web:

10. Contd. 1. HTTP (HyperText Transfer Protocol): • Is URI scheme used over the web to exchange web pages. • transmits hypertext over networks. This is the protocol of the Web. HTTP

11. I would like to open a connection GET <file location> Display response Close connection OK Send page or error message OK An HTTP conversation Client Server HTTP is the set of rules governing the format and content of the conversation between a Web client and server

12. Contd. 2. E-mail (Simple Mail Transport Protocol or SMTP): • distributes e-mail messages and attached files to one or more electronic mailboxes.

13. Contd. 3. FTP (File Transfer Protocol): • transfers files between an FTP server and a computer, for example, to download software.

14. Contd. 4. VoIP (Voice over Internet Protocol): • allows delivery of voice communications over IP networks, for example, phone calls.

15. Pages on the Web • The backbone of the World Wide Web are its files, called pages or Web pages, containing information and links to resources - both text and multimedia - throughout the Internet. • Web pages can be created by user activity. • For example, if you visit a Web search engine and enter keywords on the topic of your choice, a page will be created containing the results of your search. • In fact, a growing amount of information found on the Web today is served from databases, creating temporary Web pages "on the fly" in response to user searches

16. Contd. • Access to Web pages can be accomplished in all sorts of ways, including: • Entering a Web address into your browser and retrieving a page directly • Browsing through sites and selecting links to move from one page to another both within and beyond the site • Doing a search on a search engine to retrieve pages on the topic of your choice (See: The World of Search Engines) • Searching through directories containing links to organized collections of Web pages (See: The World of Subject Directories) • Clicking on links within e-mail messages • Using apps on social networking sites or your mobile phone to access Web and other online content

17. Retrieving files on the Web: the URL and Domain Name System • URL stands for uniform resource locator. • The URL specifies the Internet address of a file stored on a host computer, or server, connected to the Internet. • Web browsers use the URL to retrieve the file from the server. • This file is downloaded to the user's computer, or client, and displayed on the monitor connected to the machine. • Because of this relationship between clients and servers, the Web is a client-server network

18. Contd. • Underlying the functionality of a URL is a base numeric address that points to the computer that hosts the file. • This numeric address is called the ip (internet protocol) address. • The host portion of a URL is translated into its corresponding IP address using the domain name system (dns).

19. Contd. • Every file on the Internet, no matter what its protocol, has a unique URL. • Each URL points to a specific file located in a specific directory on the host machine. • This is the format of a URL: • protocol://host/path/filename

20. Contd. • For example, this is a URL from the site of the U.S. Senate of a live video stream sent by a camera pointed at the U.S. Capitol: http://www.senate.gov/general/capcam.htm • This URL is typical of addresses hosted in domains in the United States. The structure of this URL is shown below. • Protocol: http • Host computer name: www • Second-level domain name: senate • Top-level domain name: gov • Directory name: general • File name: capcam.htm

21. URI - Universal Resource Identifier • URI: Uniform Resource Identifier. The generic set of all names/addresses that are short strings that refer to resources. • URL: Uniform Resource Locator. The set of URI schemes that have explicit instructions on how to access the resource on the Internet. • URN: Uniform Resource Name. 1. An URI that has an institutional commitment to persistence, availability, etc. Note that this sort of URI may also be a URL. See, for example, PURLs. 2. A particular scheme, urn, intended to serve as persistent, location-independent, resource identifiers.

22. Data on the Web • The most basic part of a web application is the data itself. • All web applications allow a user to submit instructions on how the web application should massage a bit of data on the web server. • This might involve searching a database, creating a shopping cart of products, or emailing some information to someone, or simply do nothing as in presenting an ordinary text file.

23. Contd. • Regardless, the data which is being manipulated all has some basic characteristics. 1. Data have values 2. Data have types 3. Data have descriptions 4. Data have formats • All of the web technologies at the Data Layer define, describe, or standardize one or more of these characteristics.

24. What is web application? • Essentially, all web applications do pretty much the same things: 1. Provide a Query Interface - Web Applications provide users with an interface for entering data. 2. Transmit User-Defined Query - Once collected, the user-data is sent to a web server. 3. Perform Server Side Processing - The web server processes the user-data using some sort of "middleware". 4. "Massage" Data - Processing almost always involves playing with data on the server. 5. Transmit Query Results - The processed data is now returned to the client. 6. Perform Client Side Processing - Finally, the returned data is displayed to the user.

25. Contd.

26. DNS - Domain Name System • The World Wide Web that we know today would have not existed, if it was not for the Domain Name System. • Every day when you go online and open a website, the Domain Name System is the backend, which helps you see the website you want. • DNS represents a powerful Internet technology for converting domain names to IP addresses. • Its special mission is to be a mediator between the IP addresses, the system-side names of the websites and their respective domains, and their user-side alpha-numeric titles. • Another important function of the DNS is to control the delivery of email messages.

27. DNS - Domain Name System • The host portion of a URL is translated into its corresponding IP address using the domain name system (DNS). • The DNS is a worldwide system of servers that stores location pointers to the computers that host networked files. • Since numeric strings are difficult for humans to use, alphanumeric addresses are employed by users. • Once the translation is made by the DNS, the browser can contact the server and ask for the specific file designated in the URL.

28. Contd. • Behind every site, there is an IP address. • But, while it's easy to remember the name of a website, it's quite hard to remember the exact IP address. • For example, everybody knows about Google.com, but if you had to remember "74.125.45.100", things would have been much harder.

29. How does DNS work? • A DNS program works like this - every time a domain name is typed in a browser it is automatically passed on to a DNS server, which translates the name into its corresponding IP address (e.g. the domain name NTC Hosting.com is translated to 66.40.65.49). • Thanks to the DNS, we do not need to bother to remember complicated numeric combinations to reach a certain website - we can use its meaningful and much easier to remember domain name instead.

30. web browser • A web browser is a software application for retrieving, presenting and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video or other piece of content. • A browser is software that is used to access the internet. • A browser lets you visit websites and do activities within them like login, view multimedia, link from one site to another, visit one page from another, print, send and receive email, among many other activities • The most common browser software titles on the market are: Microsoft Internet Explorer, Google's Chrome, Mozilla Firefox, Apple Computer's Safari, and Opera.

31. HTTP Authentication Schemes(Basic Access Authentication) • The basic authentication scheme assumes that your (the client's) credentials consist of a username and a password where the latter is a secret known only to you and the server. • In the context of an HTTP transaction, basic access authentication is a method for a HTTP user agent to provide a user name and password when making a request.