111 lines
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111 lines
9.5 KiB
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Socket Iostreams</title>
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<link rel="stylesheet" href="../../../boostbook.css" type="text/css">
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<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
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<link rel="home" href="../../../index.html" title="Asio">
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<link rel="up" href="../networking.html" title="Networking">
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<link rel="prev" href="other_protocols.html" title="Support for Other Protocols">
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<link rel="next" href="bsd_sockets.html" title="The BSD Socket API and Asio">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../../asio.png"></td></tr></table>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="other_protocols.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../networking.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="bsd_sockets.html"><img src="../../../next.png" alt="Next"></a>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="asio.overview.networking.iostreams"></a><a class="link" href="iostreams.html" title="Socket Iostreams">Socket Iostreams</a>
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</h4></div></div></div>
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<p>
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Asio includes classes that implement iostreams on top of sockets. These
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hide away the complexities associated with endpoint resolution, protocol
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independence, etc. To create a connection one might simply write:
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</p>
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<pre class="programlisting"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span> <span class="identifier">stream</span><span class="special">(</span><span class="string">"www.boost.org"</span><span class="special">,</span> <span class="string">"http"</span><span class="special">);</span>
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<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">stream</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="comment">// Can't connect.</span>
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<span class="special">}</span>
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</pre>
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<p>
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The iostream class can also be used in conjunction with an acceptor to
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create simple servers. For example:
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</p>
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<pre class="programlisting"><span class="identifier">io_context</span> <span class="identifier">ioc</span><span class="special">;</span>
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<span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">endpoint</span> <span class="identifier">endpoint</span><span class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">v4</span><span class="special">(),</span> <span class="number">80</span><span class="special">);</span>
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<span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">acceptor</span> <span class="identifier">acceptor</span><span class="special">(</span><span class="identifier">ios</span><span class="special">,</span> <span class="identifier">endpoint</span><span class="special">);</span>
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<span class="keyword">for</span> <span class="special">(;;)</span>
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<span class="special">{</span>
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<span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span> <span class="identifier">stream</span><span class="special">;</span>
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<span class="identifier">acceptor</span><span class="special">.</span><span class="identifier">accept</span><span class="special">(</span><span class="identifier">stream</span><span class="special">.</span><span class="identifier">socket</span><span class="special">());</span>
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<span class="special">...</span>
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<span class="special">}</span>
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</pre>
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<p>
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Timeouts may be set by calling <code class="computeroutput"><span class="identifier">expires_at</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">expires_from_now</span><span class="special">()</span></code> to establish a deadline. Any socket operations
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that occur past the deadline will put the iostream into a "bad"
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state.
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</p>
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<p>
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For example, a simple client program like this:
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</p>
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<pre class="programlisting"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span> <span class="identifier">stream</span><span class="special">;</span>
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<span class="identifier">stream</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">60</span><span class="special">));</span>
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<span class="identifier">stream</span><span class="special">.</span><span class="identifier">connect</span><span class="special">(</span><span class="string">"www.boost.org"</span><span class="special">,</span> <span class="string">"http"</span><span class="special">);</span>
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<span class="identifier">stream</span> <span class="special"><<</span> <span class="string">"GET /LICENSE_1_0.txt HTTP/1.0\r\n"</span><span class="special">;</span>
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<span class="identifier">stream</span> <span class="special"><<</span> <span class="string">"Host: www.boost.org\r\n"</span><span class="special">;</span>
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<span class="identifier">stream</span> <span class="special"><<</span> <span class="string">"Accept: */*\r\n"</span><span class="special">;</span>
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<span class="identifier">stream</span> <span class="special"><<</span> <span class="string">"Connection: close\r\n\r\n"</span><span class="special">;</span>
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<span class="identifier">stream</span><span class="special">.</span><span class="identifier">flush</span><span class="special">();</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">stream</span><span class="special">.</span><span class="identifier">rdbuf</span><span class="special">();</span>
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</pre>
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<p>
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will fail if all the socket operations combined take longer than 60 seconds.
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</p>
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<p>
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If an error does occur, the iostream's <code class="computeroutput"><span class="identifier">error</span><span class="special">()</span></code> member function may be used to retrieve
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the error code from the most recent system call:
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</p>
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<pre class="programlisting"><span class="keyword">if</span> <span class="special">(!</span><span class="identifier">stream</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Error: "</span> <span class="special"><<</span> <span class="identifier">stream</span><span class="special">.</span><span class="identifier">error</span><span class="special">().</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span>
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<span class="special">}</span>
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</pre>
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<h6>
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<a name="asio.overview.networking.iostreams.h0"></a>
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<span><a name="asio.overview.networking.iostreams.see_also"></a></span><a class="link" href="iostreams.html#asio.overview.networking.iostreams.see_also">See
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Also</a>
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</h6>
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<p>
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<a class="link" href="../../reference/ip__tcp/iostream.html" title="ip::tcp::iostream">ip::tcp::iostream</a>,
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<a class="link" href="../../reference/basic_socket_iostream.html" title="basic_socket_iostream">basic_socket_iostream</a>,
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<a class="link" href="../../examples/cpp03_examples.html#asio.examples.cpp03_examples.iostreams">iostreams examples</a>.
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</p>
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<h6>
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<a name="asio.overview.networking.iostreams.h1"></a>
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<span><a name="asio.overview.networking.iostreams.notes"></a></span><a class="link" href="iostreams.html#asio.overview.networking.iostreams.notes">Notes</a>
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</h6>
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<p>
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These iostream templates only support <code class="computeroutput"><span class="keyword">char</span></code>,
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not <code class="computeroutput"><span class="keyword">wchar_t</span></code>, and do not perform
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any code conversion.
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</p>
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</div>
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<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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</p>
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</div>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="other_protocols.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../networking.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="bsd_sockets.html"><img src="../../../next.png" alt="Next"></a>
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</html>
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