Original subtitles

Hi guys, it's Angela from the App Brewery. And in this lesson,

we're going to deep dive into how exactly does the internet actually work

because here's this thing that we use every single day and we completely take it

for granted.

So before we start developing awesome websites and web apps for people to access

through the internet,

it's really important that we understand the fundamentals of how the internet

actually works. So what exactly is the internet? Well,

a lot of people think of it as a cloud,

something that's hanging around in the sky, it's super complex,

super difficult to understand, but actually that's not it at all.

The internet is really simple.

All it is is just a long piece of wire and the wire connects different computers

to each other.

So you might have one computer that's in Seattle and another computer that's in

London,

and they can talk to each other and transfer data through this giant wire. Now,

some of these computers attached to the internet have a very special job.

They have to be online 24/7

ready to serve you all of the data and the files that you are requesting when

you try to access websites and the computers that are doing that job,

we would call a server and the computers that any user would you use to access

the internet is called a client.

Now you can imagine a web server as a giant library, that's open 24/7,

and you can go in there at any hour of the day and request

I want to see Google's homepage,

or I want to see the latest post on Techcrunch.

And it would be able to serve you with all of the files and data that you would

need to be able to view whatever website it is that you requested.

Now you can imagine if there's a library that's big enough to house all of these

websites,

then it's going to be pretty difficult to quickly locate the thing that you want

out of this giant library, right? So how is this problem solved on the internet?

Well,

let's say that you're sitting at home on your computer and you type in google.com because

you want to head over to the main Google homepage.

What happens behind the scenes is that your browser will send a message to your

internet service provider.

So these are the people who you pay to be able to access the internet.

And if you're in the US that's a company like AT&T or Comcast,

and if you're in the UK, then that would be something like BT or Talk Talk.

Now the message that you're sending the ISP is I want to see google.com and the

ISP will then relay that message to something called a DNS server,

a domain name system server.

And a DNS server is essentially just a souped up phonebook.

And what happens when you make that request through your browser is the DNS

server will look up in its database as to what is the exact IP address

of that website that you are trying to access.

And every single computer that's connected to the internet has an IP address.

This is like a postal for your computer

so that when people need to send and receive files on the internet

each computer can be located by their unique IP address.

And once the DNS server finds the IP address,

it sends that back to your browser. So now, you know

the exact address where you can find the Google homepage.

The next thing that happens is you will send a direct request to that address

through your internet service provider.

And this message will be delivered via what's called the internet backbone.

Now the internet backbone

isn't some sort of analogy for some clever Programming.

It's literally the backbone of the internet.

And if you head over the submarinecablemap.com,

you can view all of the

underwater cables that power the internet. And the internet is made up of these

huge sprawling masses of wires

connecting all of the world's internet users. As you can imagine,

it's a pretty complex world out there. Now,

if I'm sitting in London and I want to see a website that's hosted in the

United States,

then my browser would have to make a request that goes through one of these

cables under the Atlantic ocean in order to reach the United States.

And once that computer has received my request,

they'll send back all of the relevant data, again,

through these giant cables. And to navigate all of this crazy underwater and

above water wires, all I have is an IP address.

It's like as if I'm sending a letter halfway across the world

and my only hope for my letter to reach my friend is that postal address on the

front of the envelope.

So once I've gotten the IP address of the website that I want to access,

then my browser sends another message through the internet service provider via

the internet backbone to

the server that is located at that address 216.58

210.46.

And the computer that's located at that address is of course the Google server.

And on the server there's

all of the files that I would need in order to be able to view the Google

homepage.

The server then sends all of those files back to me through the internet

backbone and I get to see the Google homepage in my browser.

And all of that happens in a matter of milliseconds.

And just to imagine the journey that my data has gone on traveling through the

world thousands of times per day.

So why don't you give it a go? Open up your browser and type in

216.58.210.46,

and hit enter to see the Google homepage being served up to you through the

internet.