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<h1>Web servers</h1>

<p>Web servers respond to

<a href="http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol">Hypertext Transfer Protocol</a> (HTTP)

requests from clients and send back a response containing a status code and

often content such as HTML, XML or JSON as well.</p>

<h2>Why are web servers necessary?</h2>

<p>Web servers are the ying to the web client's yang. The server and client speak

the standardized language of the World Wide Web. This standard language

is why an old Mozilla Netscape browser can still talk to a modern Apache or

Nginx web server, even if it cannot properly render the page design like a

modern web browser can. </p>

<p>The basic language of the Web with the request and response cycle from

client to server then server back to client remains the same as it was when

the Web was invented by

<a href="http://www.w3.org/People/Berners-Lee/">Tim Berners-Lee</a> at CERN in 1989.

Modern browsers and web servers have simply extended the language of the Web

to incorporate new standards.</p>

<h2>Client requests</h2>

<p>A client that sends a request to a web server is usually a browser such

as Internet Explorer, Firefox, or Chrome, but it can also be a</p>

<li>headless browser, commonly use for testing, such as

<a href="http://phantomjs.org/">phantomjs</a></li>

<li>commandline utility, for example <a href="https://www.gnu.org/software/wget/">wget</a>

and <a href="http://curl.haxx.se/">curl</a></li>

<li>text-based web browser such as

<a href="http://lynx.browser.org/">Lynx</a></li>

<li>web crawler. </li>

<p>Web server process requests from the above clients. The result of the web

server's processing is a

<a href="https://developer.mozilla.org/en-US/docs/HTTP/Response_codes">response code</a>

and commonly a content response. Some status codes, such as 204 (No content)

and 403 (Forbidden), do not have content responses.</p>

<p>In a simple case, the client will request a static asset such as a picture

or JavaScript file. The file sits on the file system in a location the

web server is authorized to access and the web server sends the file

to the client with a 200 status code. If the client already requested the

file and the file has not changed, the web server will pass back a 304

"Not modified" response indicating the client already has the latest version

of that file.</p>

<p><img src="theme/img/web-browser-server-requests.png" width="100%" class="technical-diagram" alt="Web server and web browser request-response cycle" /></p>

<p>A web server sends files to a web browser based on the web browser's

request. In the first request, the browser accessed the

"www.fullstackpython.com"

address and the server responded with the index.html HTML-formatted file.

That HTML file contained references to other files, such as style.css and

script.js that the browser then requested from the server.</p>

<p>Sending static assets (such as CSS and JavaScript files) can eat up a

large amount of bandwidth which is why using a Content Delivery Network

(CDN) is important when possible (see the content delivery network

section for a more detailed explanation).</p>

<h2>Web server resources</h2>

<p><a href="http://www.w3.org/Protocols/rfc2616/rfc2616.html">HTTP/1.1 Specification</a></p>

<p><a href="http://arstechnica.com/gadgets/2012/11/how-to-set-up-a-safe-and-secure-web-server/">How to set up a safe and secure Web server</a></p>

<p><a href="http://library.linode.com/web-servers/apache/mod-wsgi/ubuntu-10.04-lucid">Apache and mod_wsgi on Ubuntu 10.04</a></p>

<p><a href="http://articles.slicehost.com/nginx">Nginx web server tutorials</a></p>

<p><a href="http://carrot.is/coding/nginx_introduction">Nginx for Developers: An Introduction</a></p>

<p>An example of an <a href="http://tautt.com/best-nginx-configuration-for-security/">Nginx security configuration</a>.</p>

<p>A reference with the full list of

<a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html">HTTP status codes</a>

is provided by W3C.</p>

<p>An optimization guide for

"<a href="http://blog.zachorr.com/nginx-setup/">battle ready Nginx</a>."</p>

<p><a href="http://arstechnica.com/business/2011/11/a-faster-web-server-ripping-out-apache-for-nginx/">A faster Web server: ripping out Apache for Nginx</a></p>

<p><a href="http://ibuildings.nl/blog/2013/03/4-http-security-headers-you-should-always-be-using">4 HTTP Security Headers You Should Always Be Using</a></p>

<p><a href="http://lincolnloop.com/blog/rate-limiting-nginx/">Rate Limiting with Nginx</a>

covers how to mitigate against brute force password guessing attempts using

Nginx rate limits.</p>

<h2>Web servers learning checklist</h2>

<p><i class="fa fa-check-square-o"></i>

Choose a web server. <a href="http://nginx.org/en/">Nginx</a> is recommended although

<a href="http://httpd.apache.org/">Apache</a> is also a great choice.</p>

<p><i class="fa fa-check-square-o"></i>

Create an SSL certificate. For testing use a self-signed certificate and for a

production app buy one from <a href="http://www.digicert.com/">Digicert</a>. Configure

the web server to serve traffic over SSL. You'll need SSL for serving only

HTTPS traffic and preventing security issues that occur with unencrypted user

input.</p>

<p><i class="fa fa-check-square-o"></i>

Configure the web server to serve up static files such as CSS, JavaScript

and images.</p>

<p><i class="fa fa-check-square-o"></i>

Once you set up the <a href="/wsgi-servers.html">WSGI server</a> you'll need to configure

the web server as a pass through for dynamic content.</p>

<h3>What do you want to learn after the web server is set up?</h3>

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