What Happen when You Request a page online?
Updated: Aug 2, 2020
when you type something in, this is called the URL. Every URL has three parts. The protocol, how you want to connect, the domain, which is the server, and then optionally, you can include the document. So, even though you're typing in one URL, one of the things to realize is that usually, you're requesting lots and lots of files all at once. So, the protocols that most people have seen; the first one is HTTP, the Hypertext Transfer Protocol.The second one, HTTPS, is the same idea, only now we're having a more secure protocol. So, if you're ever connecting to a bank or any place where you're putting in passwords, make sure that the first thing you see in that URL is HTTPS. If you don't, don't connect.
The third one is called the File Transfer Protocol. It's a little bit different. When you see HTTP, it's expecting that you're going to give back and forth HTML5 code; with FTP, it could be any type of file. So, we have the protocol
The domain names are something recognizable, such as google.com, wikipedia.org. So, each of these sites has a different top-level domain. How did you get them? How do some people get to be.edu and some.com, some.biz, et cetera? Well, they're determined by ICANN. Their job is to go in and decide which types of organizations qualify for different domains. But the important thing to know is that your domain name is mapped to an address. In the old days, if he wants to connect to some place, he would type in numbers; 185.261 et cetera, et cetera. Well, there's been a new version of IP addresses, because every single client needs their own address. If you think of how many people have laptops and smartphones, we need a lot of different options. So, with these IP addresses, you basically have sets of numbers, you have these different sets right here, where each X can represent one of 16 different values. So, you can see we have a lot of options, over 300 trillion, luckily for you, the domain name server lets you type in something really simple like Google, and it's the one that turns it into that really long number.
The last part of your URL is the document. So, sometimes you want to specify a very specific document that you want to get. So, for instance, the contact page, or in this case, another one I have the file that's inside a folder. But sometimes you don't put a document at all. In fact, most of the time, you don't. If you type in wikipedia.org or Facebook.com, there's no filename. But that's okay. Every server has a default document that it's going to return. Usually, it's called index.HTML. All right. So, we figured it out. We know what it means when we're typing something in. We understand the request.
What happens though once we type that in, is we are going to get back a lot of information. Headers, cookies, form data, all the stuff that you don't see. So, the important thing to know is that the server returns files, not web pages. For a lot of us, we are very visual. So, when we type in a URL, we're looking and we're like, "Oh, here's my page." But sometimes the browser might be returning something for different types of screen readers, assistive technology, so it's not returning a web page, it's returning lots and lots of files. Hopefully, I will admit that sometimes the server can't fulfill the request. If it can't, it'll send back an error code. I think a lot of you are familiar with 404, where it says, "File not found." That usually means you typed something in wrong. If you get a 500 error, that means that the servers down. So, you may as well go have a snack, do something fun, come back later and type it in again. So, I want to do a live demo with you of what happens when we type something in. So, I've written it down for you. It looks up the domain, the DNS returns an IP address, and then a whole bunch of files start to be returned. Let's look. What I've done here is I've gone to the school of information site at the University of Michigan. I simply typed in si.umich.edu. I didn't type in the protocol because it usually just defaults. So, what you see here visually is a page. Student looking out, looking very inspired, et cetera.