Basic concepts of web development

Welcome back,

 part 2

Basic concepts of web development 

Learning objectives 

•  Understand some common terminologies related to web development like server, client, etc.
• Understand the basis steps involved in a server client communication channel.

 Welcome, 

In the previous topic, we taught about the website like what is a website and who builds it. 

 Let's go and understand that when we put the Corresponding URL of a website in the address of the browser, then how we are able to access the website.

Suppose, you have to open the project website of project754. You will enter the url project start project754.blogspot.com in the browser and the browser will send a request. Now on the basis of that request you will get a suitable response which means that your website will be open.

We will understand more about client server communication in the course.

What is a server?

Ans :- Server  is anything that provides any kind of service.

Let us understand with an example.

 Suppose, you want to eat chocolate, then you will go to the grocery store and buy a chocolate. 

 In this case the grocery store is our server or if you are ill then you will go to the doctor who will give you medicine. 

Similarly, here the doctor is our server. 

We have courted this example so that we can convince you that the server always provides a pacific type of service, which we have understand in the previous examples also.

Now let's move on to the next term. 

What is client, client is the one who asks for service from server and avails them like when you are bought chocolates then you are a client and when you go to doctor still you are a client then we can say There is one client and server always exit in pare. 

Let's go back to our chocolate example.

Now support, that this time your neighbor also has to buy chocolates. Now your neighbor will also go to the same grocery store to buy chocolates. 

 Now there are two clients here. You and your neighbor have the same server.This means that the server can provide the same type of service to multiple clients.

• Server :- server is anything that provides any kind of service.
• Client :- The client is the one who avails services from the server.

Suppose now you must have understood the meaning of client and server.

Here we have a client and a server.

• First step : Client who feel the need for a services.
• Second step: Client finds a relevant server that provides the service.
• Third step : Client get close to the service to communicate with each other.
• Fourth step: Client make the request to the server.
• Fifth step : Server acts and processes the client's request.
• Sixth step : Server sends a response to the client.

Example :- patient and doctor

Suppose, you have a client who is ill and you need to consult a doctor. 

This will be our first step: where the client will feel that he needs the service.

Then you will find a doctor near you who can help you. If you remember, this step is exactly like the second step in which the client will find a server that can provide the relevant service to him.

Then you will go to the doctor which is like the third step, going to the client-server so that he can communicate. 

Then you will request the doctor to diagnose you which is exactly like the fourth step. 

Now the fifth step is to request this server client. But will work and process it and in this case also the doctor will work on your request and do your checkup. 

And finally the doctor will give some more necessary medicines which is basically the last step of the client server communication channel. 

Now you must have understood all about the client server communication channel.

Let's move on to the next topic.

Learning objectives

• Understand some common terminologies related to web development like internet, IP address, etc.
• Understand what a web server is and its role.
• Understand how a browser and a web server communicate with each other.

Whenever we stream a movie online or buy something online dude both need one common thing to work. 

Can you guest what is that comment thing?

If you have thought internet then you are absolutely right. 

With the help of internet, we are able to connect with family and friends and do many things online and before we understand internet terms let us understand an associated terms with it.

What is network?

Network means an interconnection of computers,

if many computers are the text of the same network, then with the help of that network, they can communicate with each other.

For example, 

you can create a home network to which all the computers in your home will be connected.

Similarly,

you can also create a medium size network that will connect all the computers in your college and then we have a global network to which billions of devices are connected, which we call the Internet.

What is internet?

It is a global network to which all the computers in the world are or can be connected.

How does a website on the internet work?

Now you know what is internet and let's see you. We will look at two aspects to understand how a website works on the Internet?

• How is a server able to identify the client?

• How is a client able to identify the server?

Has it ever happened to you that you entered the URL of a website in your browser and another website opened. We can say with confidence. 

That would never have happened So now the interesting question is there are millions of websites on the internet and millions of users are trying to access them. 

But why never mix up? 

This happens because every device that connects to the Internet. They have a unique address called an IP address. The IP address is written as 13.232.219.100 in which four numbers between 0 and 255 are combined with a dot.

With the help of IP address, we can uniquely identify any computer on the network, which means that if a computer's IP address is X, it has requested google.com, then the Google server will send this response to only that computer whose IP address is will be X.

Now let's discuss the second aspect of this example.

How is a client able to identify the server?

Let's understand how a computer whose IP address is X identifies a web server such as Google and to understand this, first we will understand about the web-server and host, this is a normal computer from which you or everyone else can use it. 

This is if i install web server software on this computer then we will refer to this same computer as web server or server whenever or web server is installed on the computer then this computer hosts the website with its help.

For example,

Imagine that Google has to host its website using this computer, now because I have a web server installed on my computer, I can put Google's website online or even host it so that other users will be able to access it on the Internet.  Other words If I do not have a web server installed on my computer, I will not be able to publish or host the website there are some other technical things and aspects related to hosting but we will not go into them in detail as they are not with in the scope of this course.

So, we can say when we install web server on computer then we refer computer as a server which is web server or as a host we will refer whole course as a server. Note that all the websites that exist on the Internet have their own servers, like Google has its own server that hosts Google's website, similarly Project754 has its own server, which will host the website of Project754 and The same happens for all the websites of the world.

Now the important question is how will a browser or client know which server is hosting which website.

 Like if we have to open google.com then request will go only to google's server and not to project754's web server that means there is something in between this communication channel with the help of which browser will locate the correct web server corsponding of the website from which we have Requested.

So to help the browser find the computer which is hosting the website, there are some special computers that internet providers like airtel jio etc which provide us.This special computer which runs a software is known as DNS ( domain name server ).

DNS ( domain name server ).

This DNS maintains a table. The names of all the websites on the Internet today are mapped to their corresponding computer IP adresses in technical terms. The name is called DNS.

DNS Server

Domain Name IP Address

      google.com                    216.58.220.14

 facebook.com       69.171.230.5

      twitter.com       199.16.158.179

Do not get confused in these two terms because both of them are used interchangeably. And when the browser finds the IP from the DNS server, then that process is called DNS lookup. Now we know about the web-server, today we also know how the browser finds the relevant server.

Let's move on to the client-server communication diagram and understand it in a better way. 

First of all, we have a client which needs service, the client finds the relevant server from the DNS lookup, which will do that service provider from it. 

So that it can communicate, then the browser sends a request to the web server in which it mentions which web page it wants, which in this case is the home page of the website.

The web-server gets that page, then it sends the web page back to the browser as a response Another important thing is the special name of the request and response between the browser and the web server, from that we call HTTP request HTTP response Respectively.

 So when we get the response, it is in the form of HTML code, the browser renders this HTML code and converts it into a visual form so that we can see the website.

Now we have reached the end of this topic. 

Now its next part will be posted on Sunday.

Part 2,

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