Web Applications Architecture Review Part 1

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Time
2 hours 5 minutes
Difficulty
Beginner
CEU/CPE
3
Video Transcription
00:00
Hello, everyone, and welcome back to the course.
00:03
After a brief introduction in the last video, we can start our review
00:08
first, we'll review the Web applications, architecture and its components.
00:12
Let's start with a question.
00:14
Check this affirmation.
00:16
Web applications are examples of client server model applications.
00:20
Is this information true or false?
00:24
This information is true.
00:26
We will discuss the client server model during this video.
00:29
Let's check the learning objectives of this video.
00:33
The learning objectives of this video are to review the Web application Architecture ER and the client server model.
00:39
We will review Web application components like the Web server and clients
00:44
to start.
00:45
Let's define what a Web application is.
00:49
According to Wikipedia, a Web app is a client server application that runs in a Web browser.
00:55
The Web applications can be static or dynamic, with many features. One example of a static page is text basis or just images.
01:03
And the dynamic Web page contains a lot of scripts to change the Web page,
01:07
for example,
01:08
for two different users, the Web server can send different Web pages. It happens because the scripts identify the user.
01:15
Advertising content is a good example.
01:19
The same Web page can contain different ads for different users. That's why we say dynamic
01:23
social networks and Internet banking are good examples of dynamic pages
01:29
for each user. The social network or the Internet banking page will display different content.
01:34
Usually the dynamic content is controlled by an application server.
01:40
You will see later in this video that the application server is one of the components of modern Web applications.
01:47
Some more definitions.
01:49
Do you know what all these things are?
01:52
Internet,
01:53
a huge network composed of many other smaller networks.
01:57
For example, your cell phone is inside a smaller network, and it connects to the Internet.
02:02
Www or the World Wide Web is a specific portion of the Internet that host websites or Web pages.
02:09
It's also known as the Web
02:13
HTML,
02:15
the default language to build Web pages and Web applications.
02:17
Even if you've heard about PHP or dot net
02:21
all those languages use HTML toe work
02:24
and http
02:27
The protocol used to transmit messages by www
02:30
It's the protocol the client uses to talk with the Web server
02:36
Web application Architecture ER uses the client server model.
02:38
It's composed of two components.
02:40
The client making requests and the server answering the requests.
02:46
The request uses http protocol.
02:50
The process is like this.
02:52
We have a Web browser that request some information
02:55
it uses the http to request from the Web server.
02:59
The Web server answers the request using http, too.
03:05
With the diversity of the Internet and the increased number of services offered,
03:08
the Web application has evolved.
03:10
The number of dynamic Web pages increased Ah, lot, though it's not as common to have multi layer applications.
03:19
The clients talk with the first layer, the presentation layer that contains the Web server.
03:23
This Web server often talks with an application server.
03:29
In addition
03:30
to handle the data, it's going to use a database server as one of the components.
03:35
For example,
03:36
for a banking application, the Web server will show the Web pages.
03:39
The application server will run the processes to calculate your savings, and the database will store your name, account and savings amount.
03:47
Depending on the Web application, the Web server can talk with the application server and the database server.
03:55
Although
03:57
the client should not connect to the application or database servers,
04:00
all the communication with the client is handled by the Web server.
04:04
Nothing.
04:05
How many people access the same Web page at the same time?
04:10
Do you think that Onley one Web server can handle all the requests for information?
04:15
By the end of 2018, we had around 4.3 billion people who access the Web
04:20
to answer all of those requests. The number of servers is high. To answer all these requests, a load balanced solution is used to share the workload on the main servers.
04:31
More servers are included on all layers.
04:34
That's how it's possible for so many people to access the same resource is at the same time.
04:44
Now let's talk about Web clients.
04:46
The Web server has the Web page, and it's waiting for the request for these pages.
04:51
The client request the page to the Web server. A request sent to the Web server is a Web client job known as a user agent.
05:00
Web browsers are the most commonly known.
05:02
You use Web browsers on your computer and on your mobile phone.
05:05
Some examples are Microsoft Edge, Mozilla Firefox, Google Chrome.
05:12
Although other programs can make the same http requests as the Web browsers,
05:17
some examples are end cat tell Net curl and w get
05:23
This is easy because http is text base.
05:27
You will see learning this course. That request is some text with comments.
05:32
Here are some examples of telnet requests and Firefox
05:39
to clarify.
05:40
Let's explore the Telenet command
05:44
on a limits machine We will access to Cyberia Page using Telnet.
05:47
If successful, it will show that you are connected to Sai Buri.
05:51
In this moment, the Web server is waiting for the http request to be answered.
05:57
If we send to the server and incorrect request,
06:00
it will answer with
06:00
bad request.
06:04
Let's see one more example.
06:06
Let's try to access the Sai Buri Web page.
06:10
If you use Firefox or another Web browser, you'll get a nice picture with an error.
06:15
If you do the same, using w get you will get the same error. But in text format,
06:20
the request is the same. The answer is the same,
06:24
but how the answer is displayed is different.
06:27
W Get is a common software for Linux systems.
06:30
Let's see w get working
06:34
w get can be considered as a text basis Web browser.
06:39
First,
06:40
we will request the Sai Buri Web page.
06:43
You can see here that it worked.
06:45
Now let's request the same Web page as the example,
06:48
the Web server answered,
06:50
but
06:51
you can see the 404 error.
06:55
The basic difference between Tell Net and W get is that with Till Net, you need to craft all the requests Telnet will not send. Http request to the Web server.
07:04
W Get is like a browser. It will send the request
07:09
after talking about clients and user agents.
07:13
The next important Web application component is the Web server.
07:17
As I said before, the Web servers are responsible for answering the clients requests.
07:25
The most common Web servers today are Apache, N G I X and Microsoft Internet Information Services.
07:31
They have some differences, but they all do the expected job of a Web server.
07:36
Throughout our course, the differences will be in the logs.
07:40
If we talk about the full configurations of logging Apache at N. G. I X logs look almost the same.
07:46
Microsoft I s has a different log structure, though
07:50
we will show this difference in the next videos,
07:53
you can get more information about the Web servers on each of the listed websites.
07:57
Let's do some questions
08:03
Post assessment question
08:05
complete the sentence is
08:07
you can pause the video if you'd like
08:11
the correct sentences. W W W uses the protocol http to transmit messages through computer networks.
08:20
It uses the client server model to operate
08:24
Mozilla Firefox, Google Chrome and Microsoft Edge are examples of Web browsers.
08:28
There are programs that make requests to Web servers like Apache and JX and Microsoft I. I. S
08:35
The second answer is
08:37
Get is an example of http Method and 200 is an example of http Status Code
08:43
Video Review.
08:46
In this video, we talked about Web application architecture ER and the client server model.
08:50
We also talked about some definitions of user agents and Web servers.
08:56
In the next video, we will focus on http status codes and http methods.
09:01
We will also do a brief review of TCP slash ip protocols.
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