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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

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<title>HTTP client — cpp-netlib v0.9 documentation</title>

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<h1><a href="index.html">cpp-netlib v0.9 documentation</a></h1>

« <a href="examples_http.html" title="HTTP examples">previous</a>

</div>

<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 we are doing is creating and sending an HTTP request to a server

and printing the response body.</p>

<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="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="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="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>

</pre></div>

</div>

<h2>Building and Running The Code<a class="headerlink" href="#building-and-running-the-code" title="Permalink to this headline">¶</a></h2>

<p>To be build this example, you can follow the steps below without having to build

the whole <tt class="xref py py-mod docutils literal"><span class="pre">cpp-netlib</span></tt> distribution:</p>

<div class="highlight-python"><pre>$ cd ~/cpp-netlib

$ g++ -o http_client1 libs/network/example/http_client1.cpp \

> -I. \

> -I$BOOST_ROOT \

> -L$BOOST_ROOT/stage/lib \

> -lboost_system \

> -pthread</pre>

</div>

<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-python"><pre>$ ./http_client1 http://www.boost.org/</pre>

</div>

<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>Next we’ll develop a simple client/server application using

<tt class="docutils literal"><span class="pre">http::server</span></tt> and <tt class="docutils literal"><span class="pre">http::client</span></tt>.</p>

</div>

<h3><a href="index.html">Table Of Contents</a></h3>

<ul>

<li><a class="reference internal" href="#">HTTP client</a><ul>

<li><a class="reference internal" href="#building-and-running-the-code">Building and Running The Code</a></li>

<li><a class="reference internal" href="#diving-into-the-code">Diving into the Code</a></li>

</ul>

</li>

</ul>

<h3>Browse</h3>

<ul>

<li>Prev: <a href="examples_http.html">HTTP examples</a></li>

<li>Next: <a href="hello_world_server.html">“Hello world” HTTP server</a></li>

</ul>

<ul>

<li>

<a href="index.html">cpp-netlib v0.9 documentation</a>

<ul><li><a href="examples.html">Examples</a>

<ul><li><a href="examples_http.html">HTTP examples</a>

<ul><li>HTTP client</li></ul>

</li></ul></li></ul>

</li>

</ul>

<li><a href="_sources/http_client.txt"

rel="nofollow">Show Source</a></li>

</ul>

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