code.delx.au - learning/blob - lesson1_HTTP.html

   1 <h1>Lesson 1 HTTP</h1>
   2 <h2>References:</h2>
   3 <ul>
   4 <li>https://developer.mozilla.org/en-US/docs/Web/HTTP/Overview</li>
   5 <li>https://www.rfc-editor.org/rfc/rfc2616</li>
   6 <li>https://curl.se/docs/manpage.html</li>
   7 </ul>
   8 <h2>Overview</h2>
   9 <p>In the 1991 HTTP was created. Web browsers used HTTP to fetch static HTML, text and images from web servers. These static files were sitting in a directory on a server. The only way to change the website was to update these files.</p>
  10 <p>You could type a URL like <code>http://acme.com/products.html</code> into a graphical web browser, the browser would then speak HTTP to the <code>acme.com</code> server to fetch the <code>/products.html</code> file. The user may then click a <code>&lt;a href="http://contoso.net/about.html"&gt;</code> to cause the browser to visit a different site, speaking HTTP to the <code>contoso.net</code> server to fetch the <code>/about.html</code> file.</p>
  11 <h2>Learning objective</h2>
  12 <p>The goal is to learn about HTTP, specifically what it does and what it looks like.<br />
  13 - What is an HTTP method?<br />
  14 - What is an HTTP status code?<br />
  15 - Identify the components of a URL, server, path.<br />
  16 - How does an HTTP server use the server and path from the URL?</p>
  17 <h2>Exercises</h2>
  18 <h3>Run a simple web server using Python</h3>
  19 <ul>
  20 <li>Make new directory with some text or html files, at least two. Eg demo.html and hello.txt.</li>
  21 <li>Open terminal in that directory. Right click, open in terminal.</li>
  22 <li>Start the web server: <code>python -mhttp.server</code></li>
  23 <li>Keep this terminal window open for later.</li>
  24 </ul>
  25 <h3>Access the web server with a browser like Firefox</h3>
  26 <ul>
  27 <li>Open web browser and visit: http://localhost:8000</li>
  28 <li>See what is happening in the web server terminal window.</li>
  29 <li>You can click on the files to view them.</li>
  30 <li>The browser is acting as an HTTP client to view the files being served by the Python HTTP server.</li>
  31 </ul>
  32 <h3>Access the web server with a command line client, curl</h3>
  33 <ul>
  34 <li>Open a new terminal window in addition to the Python web server one.</li>
  35 <li>Run <code>curl http://localhost:8000</code> to see the directory index generated by the web server.</li>
  36 <li>Run <code>curl http://localhost:8000/demo.html</code> to see a file you created in the web server directory.</li>
  37 <li>Try variations of this like: <code>/hello.txt</code>, or <code>/missing.txt</code></li>
  38 <li>You can also try this on other web servers, like <code>https://www.google.com</code></li>
  39 <li>Try in verbose mode to see the raw HTTP: <code>curl -v http://localhost:8000</code></li>
  40 </ul>
  41 <h3>Access the web server by typing raw HTTP</h3>
  42 <ul>
  43 <li>Run command <code>nc localhost 8000</code></li>
  44 <li>Enter <code>GET / HTTP/1.0</code>, then press return twice</li>
  45 <li>Try with <code>GET /hello.txt</code> or other variations to see how the server responds.</li>
  46 </ul>
  47 <p>HTTP is just text! When you click a link, all that Firefox does is send this text to the server and display the result on the screen.</p>