Internet Programming Lecture 01 - Introduction (Definitions) PDF

1 040103205 Internet Programming Lecture01 - Introduction (Definitions) 1 What is the World Wide Web (WWW)? WWW is the information system that runs over the Internet WWW is global, interactive, dynamic, cross-platform, distributed, graphical hyp...

1 040103205 Internet Programming Lecture01 - Introduction (Definitions) 1 What is the World Wide Web (WWW)? WWW is the information system that runs over the Internet WWW is global, interactive, dynamic, cross-platform, distributed, graphical hypertext. 2 Hypertext Hypertext enables you to read and navigate text and visual information in a non-linear way, based on what you want to know next. An email system uses hypertext to present information. To get more information on a topic, you just click that topic. The topic takes you to a new screen that contains the new information. 3 WWW is Cross-Platform (Platform-Independent) Cross-platform means that you can access WWW equally well from any device (Mobile phone, computer of any type: IBM, Macintosh, etc.) running any operating system (Android, Windows, Linux … etc.) using any display. 4 WWW is distributed WWW is successful in providing so much information because that information is distributed globally across thousands of Web sites. 5 WWW is dynamic The owner of a website can change its contents at any time. The owner of a website should make sure that information is up-to-date.  2 6 Web site A Web site is a location on the Web that publishes information. Web site: a collection of one or more Web pages linked together. 7 Web page A web page is a single element of a Web site. 8 Web Server A web server is a computer on the Internet that stores website(s). The contents of every website are stored on a corresponding web server (either the whole server or space on it). Note To publish your website on the internet (to make your website available to everyone uses the internet), you need a web server or at least you need a domain. 9 Uniform Resource Locator Each Web site, and each page on that site, has a unique address (www.google.com). This address is called Uniform Resource Locator (URL). 10 Web Browser A Web browser is the program you use to view web pages on the internet. Web browsers sometimes are called Web clients. Examples: Microsoft Edge, Firefox, and Google Chrome. 11 Static webpages versus dynamic webpages A static webpage contains the same content each time the page is loaded and displays the same information for all users. A dynamic web page changes its content with one or more of the following factors: The time (ex. news webpages) The user (ex. preferences in a login session) Example: http://sci.p.alexu.edu.eg/Ar/Default.aspx: Authorities/privileges differs according to account type The user interaction, ex. Online Games, when you play chess against the computer online, the next move of the computer depends on your move and vice versa. 12 Domain A domain is space on a server used to store a website. A domain is a server-space.  3 13 Domain Name A domain name is a unique name that identifies a domain (ex. www.googole.com, www.hotmail.com). Having (buying) a domain means having a domain-name. If you buy a domain, then you buy a domain-name (say www.computerscience.com, no other person in the whole world can buy this domain-name). 14 Domains Name System (DNS) Hierarchy Root. 1st level (top-.net.com.eg level) domain.oracle.edu 2nd level domain 3rd level domain cloud java.mans.alexu engfac pharfac sci arts Domain Name System Hierarchy Example1: cloud.oracle.com Third-Level domain:.cloud Second-Level domain:.oracle Top-level domain:.com Example2: arts.alexu.edu.eg Fourth-Level domain:.arts Third-Level domain:.alexu Second-Level domain:.edu Top-level domain:.eg  4 There are two types of top-level domains: Generic: such as.com,.net,.org Country Code: Two letter correspond to a country such as.eg,.uk,.us 15 Web hosting Web hosting is a service that allows organizations and individuals to publish a website onto the Internet. Websites are hosted, or stored, on special computers called servers. To publish your website on the internet, you need: Domain (Domain-Name) Webhosting package : which allows you to upload your website to the domain, edit your website … etc. 15.1 Free webhosting Some hosting companies introduces webhosting for free. They allow users to have a subdomain (NOT a domain) and webhosting package. 15.1.1 Advantages of Free Webhosting 1. No money required 2. Suitable for learning purposes 3. Suitable for those users who are beginners in the webhosting field 4. Usually supports PHP and MySQL (you can write PHP code, run, and publish it in a free domain) 15.1.2 Disadvantages of Free Webhosting 1. Usually contains Advertisements 2. The user will have a subdomain NOT a domain. The user will NOT have control on the second level domain. With free webhosting you can name your subdomain, say, cs.000webhostapp.com. You can NOT name it cs.com. The second level domain 000webhostapp is fixed and you can NOT change it, you can choose the third-level domain. 3. Usually limited in bandwidth (explained later), this simply means that your website may be NOT available for some users in some time periods.  5 15.2 Shared webhosting Non-free web hosting where many websites reside on one server; each website has a space (domain) on the server. This is generally the most economical (cheap) option for hosting especially for normal users, as many people share the overall cost of the server. 15.2.1 Advantages of shared webhosting comparing to Free Webhosting 1. NO Advertisements 2. The user will have domain (NOT subdomain). The user will have control over the second level domain. 3. Usually unlimited in bandwidth, this simply means that your website will always be available for all users all time. 4. Shared hosting usually supports PHP and MySQL 15.2.2 Disadvantages (limitations) of shared webhosting The user has a domain (server space) and NOT an entire server. Notes Some webhosting companies provide "Java Hosting", this allows users to publish their "Web Java Applications" on the internet. Examples: dailyrazor.com Some webhosting companies provide "ASP.NET Hosting", this allows users to publish their "ASP.NET Applications" on the internet. Examples: dailyrazor.com and mochahost.com Note If you are beginner in the webhosting field, you should start with free webhosting. You should NOT buy shared-hosting domains until you have good experience about webhosting. 15.3 Virtual Private Server (VPS)/ Virtual Dedicated Server (VDS) In VPS/VDS environment, the provider may allow different users to share the same server, however each user is treated as if he/she has his own server. 15.3.1 Disadvantages (limitations) 1 Expensive 2 Needs experience about Server administration and configuration  6 Note Do NOT buy VPS/VDS unless you have a good experience about server administration and configuration 1.4 Dedicated webhosting Non-free web hosting in which a single user (usually an organization) owns an entire server not shared with anyone else. 16 Home pages The homepage of a web browser The home page of a web browser is the Web page that loads when you start up your browser. The homepage of a website The home page of a website is the entry (start) page of that web site (also called default document), which links to other pages on the web site. Example: oracle.com/index.html Notes When you publish your website using webhosting server, you are required to save the home page of your website using a specific name and specific extension such as "index.html" or "default.html"  7 17 Bandwidth To view (browse) a webpage on your computer, the contents of the web page must be downloaded from the server to your computer. Bandwidth is the amount of data downloaded from your server to the visitor’s computer. If your website contains large files and many visitors, then you will need a great amount of bandwidth. The less bandwidth you have, the slower it takes your website to load, regardless of visitor's connection type. The bandwidth determines how many users can visit your website every month (and hence every day) without any problems. 17.1 Calculating Bandwidth The amount of Bandwidth needed every month = x * y * z * 30 (number of days) x = Number of visitors every day y = the average page size of your website z = Number of pages that will be visited by the user The amount of data that the user will download = y * z Exercise 1 Calculate the monthly bandwidth needed of a website that consists of five pages if the average page size is 40 KB, fifty visitors are expected every day, and each of these visitors will view all pages. Exercise 2 A website that consists of ten pages, the average page size is 50 MB, the monthly bandwidth is 500 GB. How many visitors can visit this website every day if each visitor will view all pages?