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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `guide` mod in crate `mio`."><meta name="keywords" content="rust, rustlang, rust-lang, guide"><title>mio::guide - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled ><script id="default-settings"></script><script src="../../storage.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../favicon.svg">
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<link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../../down-arrow.svg");}</style></head><body class="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../mio/index.html'><div class='logo-container rust-logo'><img src='../../rust-logo.png' alt='logo'></div></a><p class="location">Module guide</p><div class="sidebar-elems"><p class="location"><a href="../index.html">mio</a></p><script>window.sidebarCurrent = {name: "guide", ty: "mod", relpath: "../"};</script><script defer src="../sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><span class="help-button">?</span>
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<a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class="fqn"><span class="out-of-band"><span id="render-detail"><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span><a class="srclink" href="../../src/mio/lib.rs.html#121-265" title="goto source code">[src]</a></span><span class="in-band">Module <a href="../index.html">mio</a>::<wbr><a class="mod" href="">guide</a></span></h1><div class="docblock"><h1 id="getting-started-guide" class="section-header"><a href="#getting-started-guide">Getting started guide.</a></h1>
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<p>In this guide we'll do the following:</p>
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<ol>
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<li>Create a <a href="../struct.Poll.html"><code>Poll</code></a> instance (and learn what it is).</li>
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<li>Register an <a href="../event/trait.Source.html">event source</a>.</li>
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<li>Create an event loop.</li>
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</ol>
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<p>At the end you'll have a very small (but quick) TCP server that accepts
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connections and then drops (disconnects) them.</p>
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<h2 id="1-creating-a-poll-instance" class="section-header"><a href="#1-creating-a-poll-instance">1. Creating a <code>Poll</code> instance</a></h2>
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<p>Using Mio starts by creating a <a href="../struct.Poll.html"><code>Poll</code></a> instance, which monitors events
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from the OS and puts them into <a href="../event/struct.Events.html"><code>Events</code></a>. This allows us to execute I/O
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operations based on what operations are ready.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="comment">// `Poll` allows for polling of readiness events.</span>
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<span class="kw">let</span> <span class="ident">poll</span> <span class="op">=</span> <span class="ident">Poll</span>::<span class="ident">new</span>()<span class="question-mark">?</span>;
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<span class="comment">// `Events` is collection of readiness `Event`s and can be filled by</span>
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<span class="comment">// calling `Poll::poll`.</span>
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<span class="kw">let</span> <span class="ident">events</span> <span class="op">=</span> <span class="ident">Events</span>::<span class="ident">with_capacity</span>(<span class="number">128</span>);</pre></div>
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<p>For example if we're using a <a href="../net/struct.TcpListener.html"><code>TcpListener</code></a>, we'll only want to
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attempt to accept an incoming connection <em>iff</em> any connections are
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queued and ready to be accepted. We don't want to waste our time if no
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connections are ready.</p>
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<h2 id="2-registering-event-source" class="section-header"><a href="#2-registering-event-source">2. Registering event source</a></h2>
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<p>After we've created a <a href="../struct.Poll.html"><code>Poll</code></a> instance that monitors events from the OS
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for us, we need to provide it with a source of events. This is done by
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registering an <a href="../event/trait.Source.html">event source</a>. As the name “event source” suggests it is
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a source of events which can be polled using a <code>Poll</code> instance. On Unix
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systems this is usually a file descriptor, or a socket/handle on
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Windows.</p>
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<p>In the example below we'll use a <a href="../net/struct.TcpListener.html"><code>TcpListener</code></a> for which we'll receive
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an event (from <a href="../struct.Poll.html"><code>Poll</code></a>) once a connection is ready to be accepted.</p>
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<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
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<span class="comment">// Create a `TcpListener`, binding it to `address`.</span>
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">listener</span> <span class="op">=</span> <span class="ident">TcpListener</span>::<span class="ident">bind</span>(<span class="ident">address</span>)<span class="question-mark">?</span>;
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<span class="comment">// Next we register it with `Poll` to receive events for it. The `SERVER`</span>
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<span class="comment">// `Token` is used to determine that we received an event for the listener</span>
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<span class="comment">// later on.</span>
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<span class="kw">const</span> <span class="ident">SERVER</span>: <span class="ident">Token</span> <span class="op">=</span> <span class="ident">Token</span>(<span class="number">0</span>);
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<span class="ident">poll</span>.<span class="ident">registry</span>().<span class="ident">register</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">listener</span>, <span class="ident">SERVER</span>, <span class="ident">Interest</span>::<span class="ident">READABLE</span>)<span class="question-mark">?</span>;</pre></div>
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<p>Multiple event sources can be <a href="../struct.Registry.html#method.register">registered</a> (concurrently), so we can
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monitor multiple sources at a time.</p>
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<h2 id="3-creating-the-event-loop" class="section-header"><a href="#3-creating-the-event-loop">3. Creating the event loop</a></h2>
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<p>After we've created a <a href="../struct.Poll.html"><code>Poll</code></a> instance and registered one or more
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<a href="../event/trait.Source.html">event sources</a> with it, we can <a href="../struct.Poll.html#method.poll">poll</a> it for events. Polling for events
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is simple, we need a container to store the events: <a href="../event/struct.Events.html"><code>Events</code></a> and need
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to do something based on the polled events (this part is up to you, we
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can't do it all!). If we do this in a loop we've got ourselves an event
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loop.</p>
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<p>The example below shows the event loop in action, completing our small
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TCP server.</p>
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<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
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<span class="comment">// Start our event loop.</span>
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<span class="kw">loop</span> {
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<span class="comment">// Poll the OS for events, waiting at most 100 milliseconds.</span>
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<span class="ident">poll</span>.<span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">events</span>, <span class="prelude-val">Some</span>(<span class="ident">Duration</span>::<span class="ident">from_millis</span>(<span class="number">100</span>)))<span class="question-mark">?</span>;
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<span class="comment">// Process each event.</span>
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<span class="kw">for</span> <span class="ident">event</span> <span class="kw">in</span> <span class="ident">events</span>.<span class="ident">iter</span>() {
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<span class="comment">// We can use the token we previously provided to `register` to</span>
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<span class="comment">// determine for which type the event is.</span>
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<span class="kw">match</span> <span class="ident">event</span>.<span class="ident">token</span>() {
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<span class="ident">SERVER</span> <span class="op">=</span><span class="op">></span> <span class="kw">loop</span> {
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<span class="comment">// One or more connections are ready, so we'll attempt to</span>
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<span class="comment">// accept them (in a loop).</span>
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<span class="kw">match</span> <span class="ident">listener</span>.<span class="ident">accept</span>() {
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<span class="prelude-val">Ok</span>((<span class="ident">connection</span>, <span class="ident">address</span>)) <span class="op">=</span><span class="op">></span> {
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Got a connection from: {}"</span>, <span class="ident">address</span>);
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},
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<span class="comment">// A "would block error" is returned if the operation</span>
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<span class="comment">// is not ready, so we'll stop trying to accept</span>
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<span class="comment">// connections.</span>
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<span class="prelude-val">Err</span>(<span class="kw-2">ref</span> <span class="ident">err</span>) <span class="kw">if</span> <span class="ident">would_block</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> <span class="kw">break</span>,
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<span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">err</span>),
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}
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}
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}
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}
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}
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<span class="kw">fn</span> <span class="ident">would_block</span>(<span class="ident">err</span>: <span class="kw-2">&</span><span class="ident">io</span>::<span class="ident">Error</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
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<span class="ident">err</span>.<span class="ident">kind</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">WouldBlock</span>
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}</pre></div>
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