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<!doctype html> <html class="no-js" lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>learnyounode Guide</title> <meta name="description" content="learn git and github"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="assets/css/style.css"> <link rel="stylesheet" href="assets/css/code.css"> <link href='assets/fonts/fonts.css' rel='stylesheet' type='text/css'> </head> <body>  <header class="site-header"> <div class="nav u-posFixed"> <ul class="nav-lang"> <li><a href="time_server.html" >English</a></li> <li><a href="time_server.es.html" >Español</a></li> <li><a href="time_server.ja.html" >日本語</a></li> <li><a href="time_server.pt-br.html" >Português (Brasil)</a></li> <li><a href="time_server.ru.html" >Русский</a></li> <li><a href="time_server.zh-cn.html" >中文 (中国)</a></li> <li><a href="time_server.zh-tw.html" >中文 (臺灣)</a></li> </ul> <div class="wrap-width u-textCenter"> <a href="juggling_async.html" <span class="u-floatLeft hand">☜</span> </a> <a class="filledblock" href="index.html">learnyounode</a> <a href="http_file_server.html" <span class="u-floatRight hand">☞</span> </a> </div> </div> <div class="wrapper"> <div class="u-floatLeft"> <span class="all-caps">CHALLENGE</span> <h2 class="challenge-name">TIME SERVER</h2> </div> <div class="u-floatRight u-textRight"> <span class="all-caps">NUMBER</span> <h2 class="challenge-name">10 / 13</h2> </div> </div> </header> <div class="wrapper"> <p>Write a <strong>TCP time server</strong>!</p> <p>Your server should listen to TCP connections on the port provided by the first argument to your program. For each connection you must write the current date & 24 hour time in the format:</p> <pre><code><span class="hljs-string">"YYYY-MM-DD hh:mm"</span> </code></pre><p>followed by a <strong>newline</strong> character. Month, day, hour and minute must be <em>zero-filled</em> to 2 integers. For example:</p> <pre><code><span class="hljs-string">"2013-07-06 17:42"</span> </code></pre><hr> <h2 id="hints">HINTS</h2> <p>For this exercise we'll be creating a raw TCP server. There's no HTTP involved here so we need to use the <code>net</code> module from Node core which has all the basic networking functions.</p> <p>The <code>net</code> module has a method named <code>net.createServer()</code> that takes a callback function. Unlike most callbacks in Node, the callback used by <code>createServer()</code> is called more than once. Every connection received by your server triggers another call to the callback. The callback function has the signature:</p> <pre><code class="lang-js"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">callback</span> <span class="hljs-params">(socket)</span> </span>{ <span class="hljs-comment">/* ... */</span> } </code></pre> <p><code>net.createServer()</code> also returns an instance of your <code>server</code>. You must call <code>server.listen(portNumber)</code> to start listening on a particular port.</p> <p>A typical Node TCP server looks like this:</p> <pre><code class="lang-js"><span class="hljs-keyword">var</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'net'</span>) <span class="hljs-keyword">var</span> server = net.createServer(<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-params">(socket)</span> </span>{ <span class="hljs-comment">// socket handling logic</span> }) server.listen(<span class="hljs-number">8000</span>) </code></pre> <p>Remember to use the port number supplied to you as the first command-line argument.</p> <p>The <code>socket</code> object contains a lot of meta-data regarding the connection, but it is also a Node duplex Stream, in that it can be both read from, and written to. For this exercise we only need to write data and then close the socket.</p> <p>Use <code>socket.write(data)</code> to write data to the socket and <code>socket.end()</code> to close the socket. Alternatively, the <code>.end()</code> method also takes a data object so you can simplify to just: <code>socket.end(data)</code>.</p> <p>Documentation on the <code>net</code> module can be found by pointing your browser here:</p> <p> <a href="../node_apidoc/net.html">/node_apidoc/net.html</a></p> <p>To create the date, you'll need to create a custom format from a <code>new Date()</code> object. The methods that will be useful are:</p> <pre><code class="lang-js">date.getFullYear() date.getMonth() <span class="hljs-comment">// starts at 0</span> date.getDate() <span class="hljs-comment">// returns the day of month</span> date.getHours() date.getMinutes() </code></pre> <p>Or, if you want to be adventurous, use the <code>strftime</code> package from npm. The <code>strftime(fmt, date)</code> function takes date formats just like the unix <code>date</code> command. You can read more about strftime at: <a href="https://github.com/samsonjs/strftime">https://github.com/samsonjs/strftime</a></p> <hr> <div class="prenext"> <div class="u-floatLeft"> <a href="juggling_async.html" class="u-inline-block all-caps">JUGGLING ASYNC <div>⤶ </div> </a> </div> <div class="u-textRight u-floatRight"> <a href="http_file_server.html" class="u-inlineBlock all-caps">HTTP FILE SERVER <div>⤷</div> </a> </div> </div> <footer>  </footer> </div> </body> </html>