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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="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<
typename <a class="link" href="../Protocol.html" title="Protocol requirements">Protocol</a>,
typename <a class="link" href="../Executor1.html" title="Executor requirements">Executor</a>,
typename Iterator,
typename <a class="link" href="../ConnectCondition.html" title="Connect condition requirements">ConnectCondition</a>>
Iterator connect(
basic_socket< Protocol, Executor > & s,
Iterator begin,
Iterator end,
ConnectCondition connect_condition,
asio::error_code & 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="asio.reference.connect.overload12.h0"></a>
<span><a name="asio.reference.connect.overload12.parameters"></a></span><a class="link" href="overload12.html#asio.reference.connect.overload12.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<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 asio::error_code& ec,
const typename Protocol::endpoint& 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">asio::error::not_found</code>. Otherwise, contains the
error from the last connection attempt.
</p></dd>
</dl>
</div>
<h6>
<a name="asio.reference.connect.overload12.h1"></a>
<span><a name="asio.reference.connect.overload12.return_value"></a></span><a class="link" href="overload12.html#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="asio.reference.connect.overload12.h2"></a>
<span><a name="asio.reference.connect.overload12.example"></a></span><a class="link" href="overload12.html#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 asio::error_code& ec,
const::tcp::endpoint& next)
{
if (ec) std::cout << "Error: " << ec.message() << std::endl;
std::cout << "Trying: " << next << std::endl;
return true;
}
};
</pre>
<p>
It would be used with the <code class="computeroutput">asio::connect</code> function as follows:
</p>
<pre class="programlisting">tcp::resolver r(my_context);
tcp::resolver::query q("host", "service");
tcp::resolver::results_type e = r.resolve(q);
tcp::socket s(my_context);
asio::error_code ec;
tcp::resolver::results_type::iterator i = asio::connect(
s, e.begin(), e.end(), my_connect_condition());
if (ec)
{
// An error occurred.
}
else
{
std::cout << "Connected to: " << i->endpoint() << std::endl;
}
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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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