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  • Hey Chris.

  • >> Hey.

  • >> I got those burgers we ordered from the restaurant.

  • >> Awesome, they look great.

  • >> Looks awesome.

  • >> I'm going to dig in here.

  • Wait a second, this doesn't look like a Hawaiian burger.

  • Where's my runny egg?

  • >> Yeah and they kind of got the wrong bun on mine, didn't they?

  • >> Dude, but did you tell them what kind of burgers we ordered?

  • No, I just called and said, I'd like two burgers to go, please.

  • And they said it'd be ready in 15 minutes.

  • >> Dude, really?

  • You gotta be more specific.

  • >> I figured they'd just know.

  • We get the same thing every time.

  • Maybe I should've told them who I was when I was ordering.

  • >> Yeah, you think?

  • Making an HTTP request is like ordering a burger at a restaurant.

  • If you don't specifically order the cheeseburger medium rare with a fried

  • egg, you might get a turkey burger on sourdough instead.

  • >> Yeah, HTTP requests likewise specify explicitly what content you're

  • looking for and how you'd like it delivered.

  • >> In this next lesson, we'll talk about how HTTP requests are used to get

  • the information that we need over the web.

  • >> HTTP requests are a basic part of how devices get information from other

  • computers on the Internet.

  • The idea is you ask for some information, you get a response, and

  • then you extract the information in a way that's useful.

  • Every time you visit a page like Google.com on your computer

  • the web browser sends an HTP request to the address that you entered.

  • It gets received by the computers on the Internet that Google owns,

  • which process the request and create a response to send back to your device.

  • Then the browser on your device interprets the response and

  • updates the screen, which is the Google home page that you probably recognize.

  • Now check this out, I'm going to give you a little sneak peak into some neat

  • developer tools in the Chrome web browser.

  • Feel free to try this out on your own.

  • To access Chrome's developer tools, I'm going to activate contacts menu.

  • That's a right-click usually, chose Inspect.

  • Now you can see Chrome developer tools has a lot of information about each page

  • and how it's drawn.

  • It's got HTML CSS and this stuff here, the Elements tab.

  • What we want is the Network tab,

  • the Network tab is going to show us what loaded to create the webpage.

  • There is a lot of different resources and

  • we'll see HTML, CSS, JavaScript and images and

  • that sort of thing all getting loaded into the page at the same time.

  • So let me do a refresh on this page, and

  • you can see all this files just loaded themselves.

  • You can even see the timeline here of how long it took for each one to load.

  • If I scroll up you can see here's the main google.com resource that we got

  • with use to get method, to retrieve the page and the status response was 200.

  • And it even tells us the size and how long it took to retrieve the page.

  • And if I resize this window a bit so I can see the content down here,

  • I can even see the request headers that made up the request that came from my

  • device and was sent to the Google servers.

  • Now the same communication and transfer happens when you request data on

  • a mobile device whether it's the web browser app viewing a website or

  • any other app using an API.

  • Apps can fetch data from some remote source across the Internet,

  • such as computers owned by the USGS.

  • Let's explore HTTP in a little more detail.

  • When we make an HTTP request, we're basically including very specific

  • directions on what information we want from another computer on a network.

  • In the request we include a uniform resource olcator or

  • URL which is the address or location of the data source that we want.

  • The URL tells us that we need to communicate with computers at USGS as

  • opposed to the computers at Google or any other organization.

  • A URL should look pretty familiar to you.

  • It's a string of characters you type into your web browser whenever you want

  • to visit a web page like google.com or udacity.com.

  • Let's take a look at this example URL.

  • The first part is called the protocol or scheme.

  • This is usually going to be http or https.

  • The next part is called the host, domain, or authority.

  • These all pretty much mean the same thing, the main identity of the web

  • resource you're connecting to like udacity.com or google.com.

  • The next part is the resource path.

  • This is analogous to a file or folder structure on your computer, or

  • some other hierarchical organization of information.

  • The final part is called the query.

  • The begin of the query is indicated by the question mark.

  • The query is an optional way to include information about things you're looking

  • for like search terms or categories of information.

Hey Chris.

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B1 中級

ネットワーク接続のご紹介 (Introdução a conexões de rede)

  • 67 14
    Shuyang に公開 2021 年 01 月 14 日
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