Protocols - Intro to Computer ScienceYouTube↗  IA↗(long shot)
Education  10.5K views 75 likes 3 dislikes   23 Feb 2015
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And what we need to make a network work is
ネットワークを機能させるためには プロトコルが必要です
a Protocol. And what a protocol is, a set of rules
プロトコルは人々が同意するルールのセットです
that people agree to, that tell you how two entities
これによって2つのエンティティが 通信を行う方法が分かります
can talk to each other. So, for the web, the protocol
Webにおいてプロトコルは
gives rules about how a client and a server talk
クライアントとサーバが通信するための ルールとなります
to each other. The client is the web browser and the server, is the web server. So that might be udacity
クライアントはWebブラウザで サーバはWebサーバのことです サーバはudacity．comかもしれません
dot com. The web browser is what you're running at home.
Webブラウザは皆さんが家で使っているソフトです
And what the protocol says is, if you want to
プロトコルが決めることは？
get the server to do something, the client has
サーバに何かを行わせたい場合は
to send a message in a particular way. The
クライアントはある特定の方法で メッセージを送らなければなりません
protocol that we use on the web, is called hypertext transfer proto, protocol. Which is abbreviated as HTTP. When
Webで使われているプロトコルは ハイパーテキスト転送プロトコルと呼ばれています これを短縮したのがHTTPです
you look in your browser, almost all the URLs that
ブラウザを見てみると
you use start with HTTP. That indicates that the
ほぼすべてのURLは httpで始まっていることが分かります
protocol, that you should use to talk to the sever,
ドキュメントのリクエスト先となるサーバと 通信を行うためには
that you're requesting a document from, is this protocol, called hyper text transfer protocol. An it's a very simple protocol.
このHTTPプロトコルを使う必要があるということを 示しているのです これはとても簡単なプロトコルです
There aren't, too many messages. There's actually only two main
メッセージの種類はあまり多くありません
messages and there is only one, we'll talk about. That's
主要なメッセージは実際は2つだけで これからお話しするのはそのうちの1つです
the message called GET. The client can send a message
それはGETと呼ばれるメッセージです クライアントがサーバにメッセージを送ると
to the server, where the message says get, and then the name of that object that you want to get.
メッセージはGETと伝えてから 求めるオブジェクトの名前を伝えます
So that's all the client does. It sense the message
クライアントはこれだけでメッセージを送れるのです
like this, and if you remember the python code for get
もしget＿pageというPythonコードを覚えていたら
page. Well, let's call in some library function that actually does
実際にこのGETを行うライブラリ関数を 呼び出してみましょう
this. That's sending the get message to the server. The server
するとGETメッセージがサーバに送られます
will get that message. It will do some, run some code
サーバはそのメッセージを取得して 何らかのコードを実行します
on it. It will find a file that was requested. It
サーバはリクエストされたファイルを見つけます
might run some more code to get the result. Take the
結果を取得するために さらにコードを実行するかもしれません
web application course to understand more about what the server does,
サーバの動作をさらに詳しく学びたい方は Webアプリケーションのコースを 受講するといいでしょう
but what matters to the client, and what matters to us
ここでクライアントにとって そしてGETを使う私たちにとって重要なのは
in using this, is what happens after that. The server
そのあとに起きることです
sends back a response, which is the contents of the
サーバはレスポンスを送り返してきます
requested object. So that's the whole protocol, that's what's going
それはリクエストしたオブジェクトのコンテンツです これがプロトコルの全体です
on whether you send a web request using your browser, by
ブラウザでリンクをクリックして Webリクエストを送る時にも同じことが起きています
clicking on a link. Well then the browsers doing a lot of things to figure out what you requested and then
その場合にはブラウザは リクエストを解明するために多くの動作を行い
its sending a get message to the right web server.
適切なWebサーバにGETメッセージを送ります
That was the server specified by the URL, to know which
送り先はURLで指定されたサーバです
server it is, and then its getting a response and its
そしてブラウザはレスポンスを受け取り
doing processing on that response to render it. If you want to
そのレスポンスを処理して表示します
understand more about what the web browser is doing, take the
Webブラウザの動作をさらに詳しく学びたい方は
programming languages class that focuses on how to build a web browser.
Webブラウザの作成に重点を置いた プログラミング言語のコースを受講するといいでしょう
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