doc/html/boost_asio/reference/connect/overload12.html


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<title>connect (12 of 12 overloads)</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.connect.overload12"></a><a class="link" href="overload12.html" title="connect (12 of 12 overloads)">connect (12
        of 12 overloads)</a>
</h4></div></div></div>
<p>
          Establishes a socket connection by trying each endpoint in a sequence.
        </p>
<pre class="programlisting">template&lt;
    typename <a class="link" href="../Protocol.html" title="Protocol requirements">Protocol</a>,
    typename Iterator,
    typename <a class="link" href="../ConnectCondition.html" title="Connect condition requirements">ConnectCondition</a>&gt;
Iterator connect(
    basic_socket&lt; Protocol &gt; &amp; s,
    Iterator begin,
    Iterator end,
    ConnectCondition connect_condition,
    boost::system::error_code &amp; ec);
</pre>
<p>
          This function attempts to connect a socket to one of a sequence of endpoints.
          It does this by repeated calls to the socket's <code class="computeroutput">connect</code> member
          function, once for each endpoint in the sequence, until a connection is
          successfully established.
        </p>
<h6>
<a name="boost_asio.reference.connect.overload12.h0"></a>
          <span class="phrase"><a name="boost_asio.reference.connect.overload12.parameters"></a></span><a class="link" href="overload12.html#boost_asio.reference.connect.overload12.parameters">Parameters</a>
        </h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">s</span></dt>
<dd><p>
                The socket to be connected. If the socket is already open, it will
                be closed.
              </p></dd>
<dt><span class="term">begin</span></dt>
<dd><p>
                An iterator pointing to the start of a sequence of endpoints.
              </p></dd>
<dt><span class="term">end</span></dt>
<dd><p>
                An iterator pointing to the end of a sequence of endpoints.
              </p></dd>
<dt><span class="term">connect_condition</span></dt>
<dd>
<p>
                A function object that is called prior to each connection attempt.
                The signature of the function object must be:
</p>
<pre class="programlisting">bool connect_condition(
    const boost::system::error_code&amp; ec,
    const typename Protocol::endpoint&amp; next);
</pre>
<p>
                The <code class="computeroutput">ec</code> parameter contains the result from the most recent
                connect operation. Before the first connection attempt, <code class="computeroutput">ec</code>
                is always set to indicate success. The <code class="computeroutput">next</code> parameter
                is the next endpoint to be tried. The function object should return
                true if the next endpoint should be tried, and false if it should
                be skipped.
              </p>
</dd>
<dt><span class="term">ec</span></dt>
<dd><p>
                Set to indicate what error occurred, if any. If the sequence is empty,
                set to <code class="computeroutput">boost::asio::error::not_found</code>. Otherwise, contains
                the error from the last connection attempt.
              </p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.connect.overload12.h1"></a>
          <span class="phrase"><a name="boost_asio.reference.connect.overload12.return_value"></a></span><a class="link" href="overload12.html#boost_asio.reference.connect.overload12.return_value">Return Value</a>
        </h6>
<p>
          On success, an iterator denoting the successfully connected endpoint. Otherwise,
          the end iterator.
        </p>
<h6>
<a name="boost_asio.reference.connect.overload12.h2"></a>
          <span class="phrase"><a name="boost_asio.reference.connect.overload12.example"></a></span><a class="link" href="overload12.html#boost_asio.reference.connect.overload12.example">Example</a>
        </h6>
<p>
          The following connect condition function object can be used to output information
          about the individual connection attempts:
        </p>
<pre class="programlisting">struct my_connect_condition
{
  bool operator()(
      const boost::system::error_code&amp; ec,
      const::tcp::endpoint&amp; next)
  {
    if (ec) std::cout &lt;&lt; "Error: " &lt;&lt; ec.message() &lt;&lt; std::endl;
    std::cout &lt;&lt; "Trying: " &lt;&lt; next &lt;&lt; std::endl;
    return true;
  }
};
</pre>
<p>
          It would be used with the <code class="computeroutput">boost::asio::connect</code> function as
          follows:
        </p>
<pre class="programlisting">tcp::resolver r(io_context);
tcp::resolver::query q("host", "service");
tcp::resolver::results_type e = r.resolve(q);
tcp::socket s(io_context);
boost::system::error_code ec;
tcp::resolver::results_type::iterator i = boost::asio::connect(
    s, e.begin(), e.end(), my_connect_condition());
if (ec)
{
  // An error occurred.
}
else
{
  std::cout &lt;&lt; "Connected to: " &lt;&lt; i-&gt;endpoint() &lt;&lt; std::endl;
}
</pre>
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        Distributed under the Boost Software License, Version 1.0. (See accompanying
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