Internet: a web of computers
This course teaches you how to build charts with React and D3.js. To get there, this foundation module covers the basics of building websites.
But building websites is not only about writing code. It's also about understanding how the internet works. And that's the topic of this lesson.
The web
The internet is called the "web" because it's nothing more than a network of interconnected computers.
The computers at the edges of this network are the ones like yours and mine, with a browser open. We call them clients. After all, we're the end customers of this system!
When you open your browser and type something like google.com (or more often windguru.cz for me), an HTTP request is sent to a server.
A server is basically a computer without a screen that runs 24/7. It holds everything you need: the HTML, CSS, and JavaScript of the website you want to visit. HTTP is a protocol — a set of rules for how to ask for that information.
If you ask properly and have the right privileges, the server sends back a response that your browser displays on screen. The website is now available.
IP Addresses & DNS
Every device connected to the internet has a unique address called an IP address. It looks like this:
142.250.80.46That's one of Google's addresses! When you want to visit google.com, your browser needs to send a request to this machine using this number.
But humans are terrible at remembering numbers like this. We prefer real words. So we created DNS (Domain Name System) — a giant phonebook that translates human-friendly names into IP addresses:
Your browser first contacts a DNS server to translate the URL into an IP address, and then sends the request there.
Try it!
Use your terminal to discover real IP addresses:
Open your terminal and run ping google.com. What IP address does Google respond from? Write it down.
Now find your own IP address. Run curl ifconfig.me in your terminal. This calls an external service that tells you your public IP.
Domain names are the human-readable addresses you buy (like mysite.com). When you "point a domain" to a server, you're creating a DNS record that says "this name = this IP."