1 00:00:17,170 --> 00:00:23,860 Let us start with the most important and most interesting section of this discourse, the Web application 2 00:00:24,010 --> 00:00:24,670 and testing. 3 00:00:25,640 --> 00:00:30,380 In this lecture, we are going to see an introduction to Web service. 4 00:00:31,950 --> 00:00:38,700 So what is a Web server, web server is a computer system that stores processes and delivers Web pages 5 00:00:38,700 --> 00:00:46,170 to the clients where it should be a web server delivers requestor Web pages to users who enter the URL 6 00:00:46,170 --> 00:00:47,060 in a Web browser. 7 00:00:47,730 --> 00:00:52,710 Every computer on the Internet that contains a website must have a website program. 8 00:00:53,490 --> 00:00:58,610 The computer in which a website or program runs is also usually called a Web server. 9 00:00:59,070 --> 00:01:05,190 So the term Web server is used to represent both the server program and the computer in which the server 10 00:01:05,190 --> 00:01:08,880 program runs for the characteristics of the server. 11 00:01:09,690 --> 00:01:16,740 A web server is just like another type of computer and it is always connected to the Internet so that 12 00:01:16,980 --> 00:01:20,040 clients can access the web pages hosted by the Web server. 13 00:01:20,670 --> 00:01:24,470 It always has an application called a Web server running application. 14 00:01:25,200 --> 00:01:30,450 In short, a Web server is a computer that is connected to the Internet or Internet. 15 00:01:31,020 --> 00:01:36,840 The website server program will always be running in the computer when a user tries to access a website 16 00:01:36,840 --> 00:01:38,150 hosted by the Web server. 17 00:01:38,970 --> 00:01:42,780 It is actually the Web server program that delivers the Web page. 18 00:01:42,780 --> 00:01:50,040 That client has asked for all Web sites in the Internet at hoster, in Web servers, sitting in various 19 00:01:50,040 --> 00:01:50,910 parts of the world. 20 00:01:52,160 --> 00:02:00,500 So is a Web server, hardware or software, mostly Web server refers to the software program that serves 21 00:02:00,500 --> 00:02:06,860 the client requests, but sometimes the computer in which the Web program is installed is also called 22 00:02:06,860 --> 00:02:07,860 as a Web server. 23 00:02:08,110 --> 00:02:11,540 Therefore, a Web server can be hardware and software. 24 00:02:12,380 --> 00:02:15,920 Now we will see how a Web server operates. 25 00:02:16,820 --> 00:02:25,610 Like when I type a portal, like w w w what is dot net and click on something I could drop into that 26 00:02:25,610 --> 00:02:26,000 page. 27 00:02:27,560 --> 00:02:30,290 But what happens behind the scenes? 28 00:02:30,650 --> 00:02:34,220 Bring you to this page and make you do this line of text. 29 00:02:34,610 --> 00:02:40,340 So now let's see what is actually happening behind the web server that is behind our browser. 30 00:02:41,030 --> 00:02:45,380 The first you might do this, you type its GDP. 31 00:02:45,380 --> 00:02:51,410 W w w dot is put it in the address bar of your browser and press your return key. 32 00:02:52,040 --> 00:02:55,700 Now, the browser could break this up into two parts. 33 00:02:56,210 --> 00:03:02,330 The protocol which we will use to connect to the server, that is GDP and the server name that is is 34 00:03:02,330 --> 00:03:03,020 put on it. 35 00:03:03,470 --> 00:03:05,840 And then the following process happens. 36 00:03:06,560 --> 00:03:11,870 The browser breaks up the URL into the parts and then it tries to communicate with the server. 37 00:03:11,870 --> 00:03:18,290 Looking for the server name server is identified through a unique IP address, but the alias of the 38 00:03:18,290 --> 00:03:22,430 IP address is Maintain the DNS server or the naming server. 39 00:03:23,560 --> 00:03:30,460 The browser looks at this naming servers, identifies the IP address on the server and requests database 40 00:03:30,670 --> 00:03:34,250 and gets the site and gets the estimate tags for the page. 41 00:03:34,900 --> 00:03:38,720 Finally, it displays the e-mail content on the browser. 42 00:03:40,180 --> 00:03:44,160 So you must have a question like, where is my Web server located? 43 00:03:45,330 --> 00:03:50,760 When you tried to access a website, you don't really need to know where the website is located, the 44 00:03:50,760 --> 00:03:57,150 web server may be located in another city or country, but all you need to do is take the URL of the 45 00:03:57,150 --> 00:03:59,220 website you want to access in the Web browser. 46 00:04:00,180 --> 00:04:06,170 The Web browser will send this information to the Internet and then it will still find the Web server. 47 00:04:06,840 --> 00:04:12,510 Once the Web server is laggardly, it delivers the specific Web page on the Web server program, running 48 00:04:12,510 --> 00:04:15,290 on the server, the web server program. 49 00:04:15,300 --> 00:04:18,790 Process your request and send the resulting the page to a browser. 50 00:04:19,440 --> 00:04:23,820 It is the responsibility of the Web browser to format and display the Web page to you. 51 00:04:25,110 --> 00:04:28,760 So how many observers are needed for a website? 52 00:04:29,730 --> 00:04:35,970 Typically there is only one website required for a website, but large websites like Yahoo, Google 53 00:04:35,970 --> 00:04:39,140 and so on will have millions of visitors every minute. 54 00:04:39,780 --> 00:04:45,900 One computer cannot possess such use number of requests, so they will have hundreds of servers deployed 55 00:04:45,900 --> 00:04:50,020 in various parts of the world so that they can provide a faster response. 56 00:04:50,430 --> 00:04:58,830 Some examples of Web server applications are Apache, and I guess in the next lecture we will see types 57 00:04:58,830 --> 00:05:00,420 of attacks on Web server.