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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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<title>HTTP client — cpp-netlib v0.10.0</title>
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<div class="section" id="http-client">
<span id="id1"></span><h1>HTTP client<a class="headerlink" href="#http-client" title="Permalink to this headline">¶</a></h1>
<p>The first code example is the simplest thing you can do with the
<tt class="xref py py-mod docutils literal"><span class="pre">cpp-netlib</span></tt>. The application is a simple HTTP client, which can
be found in the subdirectory <tt class="docutils literal"><span class="pre">libs/network/example/http_client.cpp</span></tt>.
All this example doing is creating and sending an HTTP request to a server
and printing the response body.</p>
<div class="section" id="the-code">
<h2>The code<a class="headerlink" href="#the-code" title="Permalink to this headline">¶</a></h2>
<p>Without further ado, the code to do this is as follows:</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="cp">#include <boost/network/protocol/http/client.hpp></span>
<span class="cp">#include <iostream></span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">argv</span><span class="p">[])</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">boost</span><span class="o">::</span><span class="n">network</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">argc</span> <span class="o">!=</span> <span class="mi">2</span><span class="p">)</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Usage: "</span> <span class="o"><<</span> <span class="n">argv</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o"><<</span> <span class="s">" [url]"</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">return</span> <span class="mi">1</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]);</span>
<span class="n">request</span> <span class="o"><<</span> <span class="n">header</span><span class="p">(</span><span class="s">"Connection"</span><span class="p">,</span> <span class="s">"close"</span><span class="p">);</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="n">response</span> <span class="o">=</span> <span class="n">client</span><span class="p">.</span><span class="n">get</span><span class="p">(</span><span class="n">request</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="running-the-example">
<h2>Running the example<a class="headerlink" href="#running-the-example" title="Permalink to this headline">¶</a></h2>
<p>You can then run this to get the <a class="reference external" href="http://www.boost.org/">Boost</a> website:</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nv">$ </span><span class="nb">cd</span> ~/cpp-netlib-build
<span class="nv">$ </span>make http_client
<span class="nv">$ </span>./example/http_client http://www.boost.org/
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The instructions for all these examples assume that
<tt class="xref py py-mod docutils literal"><span class="pre">cpp-netlib</span></tt> is build outside the source tree,
according to <a class="reference external" href="http://www.cmake.org/Wiki/CMake_FAQ#What_is_an_.22out-of-source.22_build.3F">CMake conventions</a>. For the sake of
consistency we assume that this is in the
<tt class="docutils literal"><span class="pre">~/cpp-netlib-build</span></tt> directory.</p>
</div>
</div>
<div class="section" id="diving-into-the-code">
<h2>Diving into the code<a class="headerlink" href="#diving-into-the-code" title="Permalink to this headline">¶</a></h2>
<p>Since this is the first example, each line will be presented and
explained in detail.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="cp">#include <boost/network/protocol/http/client.hpp></span>
</pre></div>
</div>
<p>All the code needed for the HTTP client resides in this header.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
</pre></div>
</div>
<p>First we create a <tt class="docutils literal"><span class="pre">client</span></tt> object. The <tt class="docutils literal"><span class="pre">client</span></tt> abstracts all the
connection and protocol logic. The default HTTP client is version
1.1, as specified in <a class="reference external" href="http://www.w3.org/Protocols/rfc2616/rfc2616.html">RFC 2616</a>.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]);</span>
</pre></div>
</div>
<p>Next, we create a <tt class="docutils literal"><span class="pre">request</span></tt> object, with a URI string passed as a
constructor argument.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">request</span> <span class="o"><<</span> <span class="n">header</span><span class="p">(</span><span class="s">"Connection"</span><span class="p">,</span> <span class="s">"close"</span><span class="p">);</span>
</pre></div>
</div>
<p><tt class="xref py py-mod docutils literal"><span class="pre">cpp-netlib</span></tt> makes use of stream syntax and <em>directives</em> to allow
developers to build complex message structures with greater
flexibility and clarity. Here, we add the HTTP header “Connection:
close” to the request in order to signal that the connection will be
closed after the request has completed.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="n">response</span> <span class="o">=</span> <span class="n">client</span><span class="p">.</span><span class="n">get</span><span class="p">(</span><span class="n">request</span><span class="p">);</span>
</pre></div>
</div>
<p>Once we’ve built the request, we then make an HTTP GET request
throught the <tt class="docutils literal"><span class="pre">http::client</span></tt> from which an <tt class="docutils literal"><span class="pre">http::response</span></tt> is
returned. <tt class="docutils literal"><span class="pre">http::client</span></tt> supports all common HTTP methods: GET,
POST, HEAD, DELETE.</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
<p>Finally, though we don’t do any error checking, the response body is
printed to the console using the <tt class="docutils literal"><span class="pre">body</span></tt> directive.</p>
<p>That’s all there is to the HTTP client. In fact, it’s possible to
compress this to a single line:</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="n">body</span><span class="p">(</span><span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="p">().</span><span class="n">get</span><span class="p">(</span><span class="n">http</span><span class="o">::</span><span class="n">request</span><span class="p">(</span><span class="s">"http://www.boost.org/"</span><span class="p">)));</span>
</pre></div>
</div>
<p>The next example will introduce the <tt class="docutils literal"><span class="pre">uri</span></tt> class.</p>
</div>
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<ul>
<li><a class="reference internal" href="#">HTTP client</a><ul>
<li><a class="reference internal" href="#the-code">The code</a></li>
<li><a class="reference internal" href="#running-the-example">Running the example</a></li>
<li><a class="reference internal" href="#diving-into-the-code">Diving into the code</a></li>
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