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<head>
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<style type="text/css">
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ul {
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</style>
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<script type="text/javascript" src="sh_main.js"></script>
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<script type="text/javascript" src="sh_javascript.min.js"></script>
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<link type="text/css" rel="stylesheet" href="pipe.css" />
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<title>node.js</title>
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</head>
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<body>
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<div id="toc">
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<ol>
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<li><a href="#download">Download</a></li>
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<li><a href="https://github.com/joyent/node/raw/master/ChangeLog">ChangeLog</a></li>
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<li><a href="#about">About</a></li>
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<li><a href="http://nodejs.org/docs/v0.4.2/api">v0.4.2 docs</a></li>
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<br/>
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<li><B><a href="https://github.com/joyent/node/wiki">Wiki</a></B></li>
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</ol>
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</div>
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<div id="content">
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<!-- <h1><a href="http://nodejs.org/">Node</a></h1> -->
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<img id="logo" src="logo.png" alt="node.js"/>
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<p id="introduction">
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Evented I/O for
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<a href="http://code.google.com/p/v8/">V8 JavaScript</a>.
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</p>
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<p>
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An example of a web server written in Node which responds with
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"Hello World" for every request.
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</p>
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<pre>
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var http = require('http');
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http.createServer(function (req, res) {
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res.writeHead(200, {'Content-Type': 'text/plain'});
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res.end('Hello World\n');
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}).listen(8124, "127.0.0.1");
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console.log('Server running at http://127.0.0.1:8124/');
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</pre>
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<p>
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To run the server, put the code into a file
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<code>example.js</code> and execute it with the <code>node</code>
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program:
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</p>
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<pre class="sh_none">
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% node example.js
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Server running at http://127.0.0.1:8124/</pre>
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<p>
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Here is an example of a simple TCP server which listens on port 8124
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and echoes whatever you send it:
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</p>
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<pre>
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var net = require('net');
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var server = net.createServer(function (socket) {
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socket.write("Echo server\r\n");
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socket.pipe(socket);
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})
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server.listen(8124, "127.0.0.1");
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</pre>
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<p>
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See the <a href="/docs">API documentation</a> for more
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examples.
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</p>
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<p>
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Go to <a href="https://github.com/joyent/node/wiki">the Wiki</a> for lots more information.
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</p>
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<h2 id="download">Download</h2>
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<p>
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<a href="http://github.com/joyent/node/tree/master">git repo</a>
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</p>
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<p>
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2011.03.02
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<a href="http://nodejs.org/dist/node-v0.4.2.tar.gz">node-v0.4.2.tar.gz</a>
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(<a href="http://nodejs.org/docs/v0.4.2/api/index.html">Documentation</a>)
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</p>
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<p>Historical: <a href="http://nodejs.org/dist">versions</a>, <a href="http://nodejs.org/docs">docs</a></p>
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<p>
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For build instructions see
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<a href="https://github.com/joyent/node/wiki/Installation">https://github.com/joyent/node/wiki/Installation</a>
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</p>
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<h2 id="about">About</h2>
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<p>
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Node's goal is to provide an easy way to build scalable network
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programs. In the "hello world" web server example above, many
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client connections can be handled concurrently. Node tells the
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operating system (through <code>epoll</code>, <code>kqueue</code>,
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<code class="sh_none">/dev/poll</code>, or <code>select</code>)
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that it should be notified when a new connection is made, and
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then it goes to sleep. If someone new connects, then it executes
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the callback. Each connection is only a small heap allocation.
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</p>
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<p>
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This is in contrast to today's more common concurrency model where
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OS threads are employed. Thread-based networking is relatively
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inefficient and very difficult to use. See:
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<a href="http://www.kegel.com/c10k.html">this</a> and
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<a href="http://bulk.fefe.de/scalable-networking.pdf">this.</a>
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Node will show much better memory efficiency under high-loads
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<!-- TODO benchmark -->
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than systems which allocate 2mb thread stacks for each connection.
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Furthermore, users of Node are free from worries of dead-locking
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the process—there are no locks. Almost no function in Node
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directly performs I/O, so the process never blocks. Because
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nothing blocks, less-than-expert programmers are able to develop
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fast systems.
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</p>
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<p>
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Node is similar in design to and influenced by systems like Ruby's <a
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href="http://rubyeventmachine.com/">Event Machine</a> or Python's <a
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href="http://twistedmatrix.com/">Twisted</a>. Node takes the event
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model a bit further—it presents the event loop as a language
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construct instead of as a library. In other systems there is always
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a blocking call to start the event-loop. Typically one defines
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behavior through callbacks at the beginning of a script and at the
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end starts a server through a blocking call like
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<code>EventMachine::run()</code>. In Node there is no such
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start-the-event-loop call. Node simply enters the event loop after
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executing the input script. Node exits the event loop when there are
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no more callbacks to perform. This behavior is like browser
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javascript—the event loop is hidden from the user.
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</p>
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<p>
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HTTP is a first class protocol in Node. Node's HTTP library has
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grown out of the author's experiences developing and working with
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web servers. For example, streaming data through most web frameworks
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is impossible. Node attempts to correct these problems in its HTTP
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<a href="http://github.com/ry/http-parser/tree/master">parser</a>
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and API. Coupled with Node's purely evented infrastructure, it makes
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a good foundation for web libraries or frameworks.
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</p>
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<p>
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<i>
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But what about multiple-processor concurrency? Aren't threads
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necessary to scale programs to multi-core computers?
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</i>
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Processes are necessary to scale to multi-core computers, not
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memory-sharing threads. The fundamentals of scalable systems are
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fast networking and non-blocking design—the rest is message
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passing. In future versions, Node will be able to fork new
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processes (using the <a
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href="http://www.whatwg.org/specs/web-workers/current-work/"> Web
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Workers API </a>) which fits well into the current design.
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</p>
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<p>
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See also:
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<ul>
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<li><a href="http://s3.amazonaws.com/four.livejournal/20091117/jsconf.pdf">slides</a> from JSConf 2009</li>
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<li><a href="http://nodejs.org/jsconf2010.pdf">slides</a> from JSConf 2010</li>
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<li><a href="http://www.yuiblog.com/blog/2010/05/20/video-dahl/">video</a> from a talk at Yahoo in May 2010</li>
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</ul>
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</p>
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</div>
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<div style="float: right;">
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<a
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href='https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String'
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title='JS String match'><img
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src='http://static.jsconf.us/promotejsh.gif' height='150' width='180'
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alt='JS String match'/></a>
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</div>
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<a href="http://no.de/"><img src="sponsored.png" height="58" width="120"/></a>
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<div style="clear: both; font-size: 8pt">
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Copyright 2010 Joyent, Inc
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