1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Simple HTTP Client ��</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. Boost.Beast"> 8<link rel="up" href="../quick_start.html" title="Quick Look"> 9<link rel="prev" href="../quick_start.html" title="Quick Look"> 10<link rel="next" href="websocket_client.html" title="Simple WebSocket Client ��"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="../quick_start.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../quick_start.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="websocket_client.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="beast.quick_start.http_client"></a><a class="link" href="http_client.html" title="Simple HTTP Client ��">Simple HTTP Client ��</a> 28</h3></div></div></div> 29<p> 30 Use HTTP to make a GET request to a website and print the response: 31 </p> 32<p> 33 File: <a href="../../../../example/http/client/sync/http_client_sync.cpp" target="_top">http_sync_client.cpp</a> 34 </p> 35<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">beast</span><span class="special">/</span><span class="identifier">core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 36<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">beast</span><span class="special">/</span><span class="identifier">http</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 37<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">beast</span><span class="special">/</span><span class="identifier">version</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 38<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">connect</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 39<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">ip</span><span class="special">/</span><span class="identifier">tcp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 40<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cstdlib</span><span class="special">></span> 41<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 42<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> 43 44<span class="keyword">namespace</span> <span class="identifier">beast</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">beast</span><span class="special">;</span> <span class="comment">// from <boost/beast.hpp></span> 45<span class="keyword">namespace</span> <span class="identifier">http</span> <span class="special">=</span> <span class="identifier">beast</span><span class="special">::</span><span class="identifier">http</span><span class="special">;</span> <span class="comment">// from <boost/beast/http.hpp></span> 46<span class="keyword">namespace</span> <span class="identifier">net</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">;</span> <span class="comment">// from <boost/asio.hpp></span> 47<span class="keyword">using</span> <span class="identifier">tcp</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">;</span> <span class="comment">// from <boost/asio/ip/tcp.hpp></span> 48 49<span class="comment">// Performs an HTTP GET and prints the response</span> 50<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span><span class="special">**</span> <span class="identifier">argv</span><span class="special">)</span> 51<span class="special">{</span> 52 <span class="keyword">try</span> 53 <span class="special">{</span> 54 <span class="comment">// Check command line arguments.</span> 55 <span class="keyword">if</span><span class="special">(</span><span class="identifier">argc</span> <span class="special">!=</span> <span class="number">4</span> <span class="special">&&</span> <span class="identifier">argc</span> <span class="special">!=</span> <span class="number">5</span><span class="special">)</span> 56 <span class="special">{</span> 57 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> 58 <span class="string">"Usage: http-client-sync <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n"</span> <span class="special"><<</span> 59 <span class="string">"Example:\n"</span> <span class="special"><<</span> 60 <span class="string">" http-client-sync www.example.com 80 /\n"</span> <span class="special"><<</span> 61 <span class="string">" http-client-sync www.example.com 80 / 1.0\n"</span><span class="special">;</span> 62 <span class="keyword">return</span> <span class="identifier">EXIT_FAILURE</span><span class="special">;</span> 63 <span class="special">}</span> 64 <span class="keyword">auto</span> <span class="keyword">const</span> <span class="identifier">host</span> <span class="special">=</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">1</span><span class="special">];</span> 65 <span class="keyword">auto</span> <span class="keyword">const</span> <span class="identifier">port</span> <span class="special">=</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">2</span><span class="special">];</span> 66 <span class="keyword">auto</span> <span class="keyword">const</span> <span class="identifier">target</span> <span class="special">=</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">3</span><span class="special">];</span> 67 <span class="keyword">int</span> <span class="identifier">version</span> <span class="special">=</span> <span class="identifier">argc</span> <span class="special">==</span> <span class="number">5</span> <span class="special">&&</span> <span class="special">!</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">strcmp</span><span class="special">(</span><span class="string">"1.0"</span><span class="special">,</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">4</span><span class="special">])</span> <span class="special">?</span> <span class="number">10</span> <span class="special">:</span> <span class="number">11</span><span class="special">;</span> 68 69 <span class="comment">// The io_context is required for all I/O</span> 70 <span class="identifier">net</span><span class="special">::</span><span class="identifier">io_context</span> <span class="identifier">ioc</span><span class="special">;</span> 71 72 <span class="comment">// These objects perform our I/O</span> 73 <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span> <span class="identifier">resolver</span><span class="special">(</span><span class="identifier">ioc</span><span class="special">);</span> 74 <span class="identifier">beast</span><span class="special">::</span><span class="identifier">tcp_stream</span> <span class="identifier">stream</span><span class="special">(</span><span class="identifier">ioc</span><span class="special">);</span> 75 76 <span class="comment">// Look up the domain name</span> 77 <span class="keyword">auto</span> <span class="keyword">const</span> <span class="identifier">results</span> <span class="special">=</span> <span class="identifier">resolver</span><span class="special">.</span><span class="identifier">resolve</span><span class="special">(</span><span class="identifier">host</span><span class="special">,</span> <span class="identifier">port</span><span class="special">);</span> 78 79 <span class="comment">// Make the connection on the IP address we get from a lookup</span> 80 <span class="identifier">stream</span><span class="special">.</span><span class="identifier">connect</span><span class="special">(</span><span class="identifier">results</span><span class="special">);</span> 81 82 <span class="comment">// Set up an HTTP GET request message</span> 83 <span class="identifier">http</span><span class="special">::</span><span class="identifier">request</span><span class="special"><</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">string_body</span><span class="special">></span> <span class="identifier">req</span><span class="special">{</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">verb</span><span class="special">::</span><span class="identifier">get</span><span class="special">,</span> <span class="identifier">target</span><span class="special">,</span> <span class="identifier">version</span><span class="special">};</span> 84 <span class="identifier">req</span><span class="special">.</span><span class="identifier">set</span><span class="special">(</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">field</span><span class="special">::</span><span class="identifier">host</span><span class="special">,</span> <span class="identifier">host</span><span class="special">);</span> 85 <span class="identifier">req</span><span class="special">.</span><span class="identifier">set</span><span class="special">(</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">field</span><span class="special">::</span><span class="identifier">user_agent</span><span class="special">,</span> <span class="identifier">BOOST_BEAST_VERSION_STRING</span><span class="special">);</span> 86 87 <span class="comment">// Send the HTTP request to the remote host</span> 88 <span class="identifier">http</span><span class="special">::</span><span class="identifier">write</span><span class="special">(</span><span class="identifier">stream</span><span class="special">,</span> <span class="identifier">req</span><span class="special">);</span> 89 90 <span class="comment">// This buffer is used for reading and must be persisted</span> 91 <span class="identifier">beast</span><span class="special">::</span><span class="identifier">flat_buffer</span> <span class="identifier">buffer</span><span class="special">;</span> 92 93 <span class="comment">// Declare a container to hold the response</span> 94 <span class="identifier">http</span><span class="special">::</span><span class="identifier">response</span><span class="special"><</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">dynamic_body</span><span class="special">></span> <span class="identifier">res</span><span class="special">;</span> 95 96 <span class="comment">// Receive the HTTP response</span> 97 <span class="identifier">http</span><span class="special">::</span><span class="identifier">read</span><span class="special">(</span><span class="identifier">stream</span><span class="special">,</span> <span class="identifier">buffer</span><span class="special">,</span> <span class="identifier">res</span><span class="special">);</span> 98 99 <span class="comment">// Write the message to standard out</span> 100 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">res</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 101 102 <span class="comment">// Gracefully close the socket</span> 103 <span class="identifier">beast</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span> 104 <span class="identifier">stream</span><span class="special">.</span><span class="identifier">socket</span><span class="special">().</span><span class="identifier">shutdown</span><span class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">::</span><span class="identifier">shutdown_both</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span> 105 106 <span class="comment">// not_connected happens sometimes</span> 107 <span class="comment">// so don't bother reporting it.</span> 108 <span class="comment">//</span> 109 <span class="keyword">if</span><span class="special">(</span><span class="identifier">ec</span> <span class="special">&&</span> <span class="identifier">ec</span> <span class="special">!=</span> <span class="identifier">beast</span><span class="special">::</span><span class="identifier">errc</span><span class="special">::</span><span class="identifier">not_connected</span><span class="special">)</span> 110 <span class="keyword">throw</span> <span class="identifier">beast</span><span class="special">::</span><span class="identifier">system_error</span><span class="special">{</span><span class="identifier">ec</span><span class="special">};</span> 111 112 <span class="comment">// If we get here then the connection is closed gracefully</span> 113 <span class="special">}</span> 114 <span class="keyword">catch</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">exception</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span> 115 <span class="special">{</span> 116 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="string">"Error: "</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 117 <span class="keyword">return</span> <span class="identifier">EXIT_FAILURE</span><span class="special">;</span> 118 <span class="special">}</span> 119 <span class="keyword">return</span> <span class="identifier">EXIT_SUCCESS</span><span class="special">;</span> 120<span class="special">}</span> 121</pre> 122</div> 123<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 124<td align="left"></td> 125<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 126 Falco<p> 127 Distributed under the Boost Software License, Version 1.0. (See accompanying 128 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>) 129 </p> 130</div></td> 131</tr></table> 132<hr> 133<div class="spirit-nav"> 134<a accesskey="p" href="../quick_start.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../quick_start.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="websocket_client.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 135</div> 136</body> 137</html> 138
