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432 lines
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432 lines
12 KiB
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#content {
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padding-left: 2em;
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}
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}
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dt {
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color: #aaf;
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font-weight: bold;
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}
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margin: 1em 0;
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a { color: #cd5; text-decoration: none; }
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background: #733;
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padding: 0.2em 0;
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}
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</style>
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<title>node.js</title>
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<body>
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<div id="toc">
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<ol>
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<li><a href="#motivation">Motivation</a></li>
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<li><a href="#benchmarks">Benchmarks</a></li>
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<li><a href="#download">Download</a></li>
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<li><a href="#install">Build</a></li>
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<li><a href="#api">API</a>
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<ol>
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<li><a href="#timers">Timers</a>
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<li><a href="#files">File System</a>
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<li><a href="#tcp">TCP</a>
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<li><a href="#http">HTTP</a>
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<ol>
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<li><a href="#http_server">Server</a>
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<li><a href="#http_client">Client</a>
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</ol>
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<li><a href="#modules">Modules</a>
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</ol>
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</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://tinyclouds.org/node">Node</a></h1>
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<p id="introduction"> Node is a purely asynchronous I/O framework for <a
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href="http://code.google.com/p/v8/">V8 javascript</a>.
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<p>This is an example of a web server written with Node which responds with
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"Hello World" after waiting two seconds:
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<pre class="sh_javascript">
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new node.http.Server(function (msg) {
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setTimeout(function () {
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msg.sendHeader(200, [["Content-Type", "text/plain"]]);
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msg.sendBody("Hello World");
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msg.finish();
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}, 2000);
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}).listen(8000, "localhost");
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</pre>
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<p> This script can handle hundreds of concurrent requests while using
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little CPU or memory—<a href="#benchmarks">see benchmarks</a>.
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Check out <a href="#api">the documentation</a> for more examples.
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<p> Node is free to <a href="#download">download</a>, <a
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href="#api">use</a>, and <a href="#modules">build upon</a>.</p>
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<h2 id="motivation">Motivation</h2>
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<h3>Evented Programming Makes More Sense</h3>
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difference between blocking/non-blocking design
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<p> There are many methods to write internet servers but they can
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fundamentally be divided into two camps: evented and threaded; non-blocking
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and blocking. A blocking server accepts a connection and launches a new
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thread to handle the connection. Because the concurrency is handled by
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the thread scheduler, a blocking server can make function calls which
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preform full network requests.
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<pre class="sh_javascript">var response = db.execute("SELECT * FROM table");
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// do something</pre>
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<p> An evented server manages its concurrency itself. All connections
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are handled in a single thread and callbacks are executed on certain
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events: "socket 23 is has data to read", "socket 65's write buffer is
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empty". An evented server executes small bits of code but never
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<i>blocks</i> the process. In the evented world callbacks are used
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instead of functions
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<pre class="sh_javascript">db.execute("SELECT * FROM table", function (response) {
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// do something
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});</pre>
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<p><a href="http://duartes.org/gustavo/blog/post/what-your-computer-does-while-you-wait">I/O latency</a>
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<pre>
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l1 cache ~ 3
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l2 cache ~ 14
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ram ~ 250
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disk ~ 41000000
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network ~ 240000000
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</pre>
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<p>purely evented interfaces rule out a lot of stupidity
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<h3>Evented programs are more efficient</h3>
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<ol>
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<li>pthread stack size
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2mb default stack size on linux (1mb on windows, 64kb on FreeBSD)
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of course this is adjustable
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<li>context switching benchmark
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<li>Apache vs. Nginx
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<li>event machine vs mongrel (neverblock)
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</ol>
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<h3>The appropriateness of Javascript</h3>
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<ol>
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<li>No I/O
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<p> Javascript is without I/O. In the browser the DOM provides I/O,
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but non-browser javascript interpreters have only non-standardized
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functions to allow them print to console or access the network.
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<li>No Threads
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<li>Good compiler
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<li>Universality of the language
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<p> Contemporary computer infrastructure has two irreplaceable
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languages: C and Javascript. C is the language of operating systems.
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POSIX, the universal operating system API, is defined in C. So while you
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can interface with operating systems in Java and Haskell, those
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languages access must make system calls in C. Similarly, Javascript is
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the language of the web operating system. In place of POSIX is the
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DOM. You can wrap Javascript, you can compile to Javascript, but in the
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end browsers must be interfaced with in Javascript. Portable low-level
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systems tend to be written in C and portable web-level systems are
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written in Javascript.
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</ol>
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<h2 id="benchmarks">Benchmarks</h2>
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<p> TODO
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<h2 id="download">Download</h2>
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<p> TODO
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<h2 id="build">Build</h2>
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<pre>configure
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make
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make install</pre>
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<h2 id="api">Application Programming Interface</h2>
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<p> The node executable should be given an argument pointing to a
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javascript file.
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<h3 id="timers">Timers</h3>
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<p>The timer API is the same as in the browser. The functions
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<code>setTimeout, setInterval, clearTimeout, and clearInterval</code>
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<h3 id="files">File System</h3>
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<h3 id="tcp">TCP</h3>
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<h3 id="http">HTTP (<code>node.http</code>)</h3>
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<p> Node provides a fast web server and client interface. The interface is
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rather low-level. Node, for example, will not parse
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<code>application/x-www-form-urlencoded</code> message bodies—that is
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for higher level code to manage. The interface does abstract the
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Transfer-Encoding (i.e. chuncked or identity), Message boundarys, and
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Keep-Alive connections.
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<h4 id="http_server">HTTP Server (<code>node.http.Server</code>)</h4>
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<dl>
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<dt><code>new Server(request_handler, options)</code></dt>
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<dd>
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<p>Creates a new web server. The <code>options</code> argument accepts
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the same values as the options argument for
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<code>node.tcp.Server</code> does. The options argument is optional.
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<p>The <code>request_handler</code> is a function which is called on
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each request with a <code>Message</code> object argument.
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</dd>
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<dt><code>server.listen(port, hostname)</code>
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<dd>
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<p>Begin accepting connections on the specified port and hostname. If the
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hostname is omitted, the server will accept connections directed to any
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address.
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</dd>
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<dt><code>server.close()</code>
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<dd>
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<p>Stops the server. Requests currently in progress will not be
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interrupted.
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</dd>
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</dl>
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<h4>HTTP Request Message (<code>node.http.Message</code>)</h4>
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<p> This object is only created internally—not by the user. It is passed
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as an argument to the <code>request_handler</code> function in a web server.
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<dl>
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<dt><code>msg.method</code>
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<dd>The request method as a string. Read only. Example: <code>"GET"</code>,
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<code>"DELETE"</code>.</dd>
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<dt><code>msg.uri</code>
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<dd>The request URI as a string. Read only.
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Example: <code>"/index.html?hello=world"</code>.</dd>
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<dt><code>msg.headers</code>
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<dd>The request headers expressed as an array of 2-element arrays. Read only.
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Example:
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<pre>
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[ ["Content-Length", "123"]
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, ["Content-Type", "text/plain"]
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, ["Connection", "keep-alive"]
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, ["Accept", "*/*"]
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]
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</pre>
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<dt><code>msg.http_version</code></dt>
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<dd>The HTTP protocol version as a string. Read only. Examples: <code>"1.1"</code>,
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<code>"1.0"</code>
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<dt><code>msg.connection</code></dt>
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<dd> A reference to the <code>node.tcp.Connection</code> object. Read
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only. Note that multiple messages can be sent on a single connection.
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</dd>
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<dt><code>msg.onBody</code></dt>
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<dd>Callback. Should be set by the user to be informed of when a piece
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of the message body is received. Example:
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<pre>
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msg.onBody = function (chunk) {
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puts("part of the body: " + chunk);
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}
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</pre>
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A chunk of the body is given as the single argument. The transfer-encoding
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has been removed.
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<p>The body chunk is either a String in the case of utf8 encoding or an
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array of numbers in the case of raw encoding.
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<dt><code>msg.onBodyComplete</code></dt>
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<dd>Callback. Made exactly once for each message. No arguments. After
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<code>onBodyComplete</code> is executed <code>onBody</code> will no longer be called.
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</dd>
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<dt><code>msg.setBodyEncoding(encoding)</code></dt>
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<dd>
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Set the encoding for the request body. Either <code>"utf8"</code> or
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<code>"raw"</code>. Defaults to raw.
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<big>TODO</big>
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<dt><code>msg.sendHeader(status_code, headers)</code></dt>
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<dd>
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Sends a response header to the request. The status code is a 3-digit
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HTTP status code, like <code>404</code>. The second argument,
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<code>headers</code>, should be an array of 2-element arrays,
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representing the response headers.
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<p>Example:
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<pre>
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var body = "hello world";
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msg.sendHeader( 200
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, [ ["Content-Length", body.length]
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, ["Content-Type", "text/plain"]
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]
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);
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</pre>
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This method must only be called once on a message and it must be called
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before <code>msg.finish()</code> is called.
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</dd>
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<dt><code>msg.sendBody(chunk)</code></dt>
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<dd>
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This method must be called after <code>sendHeader</code> was called. It
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sends a chunk of the response body. This method may be called multiple
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times to provide successive parts of the body.
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</dd>
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<dt><code>msg.finish()</code></dt>
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<dd>
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This method signals that all of the response headers and body has been
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sent; that server should consider this message complete.
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The method, <code>msg.finish()</code>, MUST be called on each response.
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</dl>
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<h3 id="modules">Modules</h3>
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<p>Node has simple module loading. Here is an example. This is the file
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<code>foo.js</code>:
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<pre>
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include("mjsunit");
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function onLoad () {
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assertEquals(1, 2);
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}
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</pre>
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<p>Here the module <code>mjsunit</code> has provided the function
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<code>assertEquals()</code>.
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<p> The module file, <code>mjsunit.js</code>, must be in the same directory
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as <code>foo.js</code> for <code>include()</code> to work. The
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<code>include()</code> function will insert all the exported objects from the
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module into the global namespace.
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<p> Because file loading does not happen instantaneously, and because Node
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has a policy of never blocking, the callback <code>onLoad()</code> is
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provided to notify the user when all the exported functions are completely
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loaded.
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<p> To export an object, add to the special object <code class="highlight">exports</code>.
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Let's look at how <code>mjsunit.js</code> does this
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<pre>
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function fail (expected, found, name_opt) {
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// ...
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}
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function deepEquals (a, b) {
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// ...
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}
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<span class="highlight">exports</span>.assertEquals = function (expected, found, name_opt) {
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if (!deepEquals(found, expected)) {
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fail(expected, found, name_opt);
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}
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};
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</pre>
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<p> The functions <code>fail</code> and <code>deepEquals</code> are not
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exported and remain private to the module.
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<p> In addition to <code>include()</code> a module can use
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<code>require()</code>. Instead of loading the exported objects into the
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global namespace, it will return a namespace object. Again, the members of
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the namespace object can only be guaranteed to exist after the
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<code>onLoad()</code> callback is made. For example:
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<pre>
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var mjsunit = require("mjsunit");
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function onLoad () {
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mjsunit.assertEquals(1, 2);
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}
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</pre>
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</body>
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</html>
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