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

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

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

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for granted.

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

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through the internet,

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

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

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a lot of people think of it as a cloud,

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

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

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The internet is really simple.

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

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to each other.

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

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London,

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

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

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They have to be online 24/7

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

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

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

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the internet is called a client.

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

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

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I want to see Google's homepage,

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or I want to see the latest post on Techcrunch.

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

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

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

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websites,

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

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

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Well,

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

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you want to head over to the main Google homepage.

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

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internet service provider.

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

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

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

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

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

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a domain name system server.

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

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

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

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of that website that you are trying to access.

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

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This is like a postal for your computer

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

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each computer can be located by their unique IP address.

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And once the DNS server finds the IP address,

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

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the exact address where you can find the Google homepage.

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

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through your internet service provider.

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

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Now the internet backbone

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

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It's literally the backbone of the internet.

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And if you head over the submarinecablemap.com,

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you can view all of the

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

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huge sprawling masses of wires

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

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

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

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United States,

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

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

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And once that computer has received my request,

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

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

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

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

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

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front of the envelope.

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

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

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the internet backbone to

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the server that is located at that address 216.58

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210.46.

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

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And on the server there's

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

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homepage.

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

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

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And all of that happens in a matter of milliseconds.

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

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world thousands of times per day.

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

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216.58.210.46,

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

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internet.