198 lines
9.0 KiB
HTML
198 lines
9.0 KiB
HTML
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
|
|
<title>async_connect (6 of 6 overloads)</title>
|
|
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
|
|
<link rel="home" href="../../../boost_asio.html" title="Boost.Asio">
|
|
<link rel="up" href="../async_connect.html" title="async_connect">
|
|
<link rel="prev" href="overload5.html" title="async_connect (5 of 6 overloads)">
|
|
<link rel="next" href="../async_initiate.html" title="async_initiate">
|
|
</head>
|
|
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
|
<table cellpadding="2" width="100%"><tr>
|
|
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
|
|
<td align="center"><a href="../../../../../index.html">Home</a></td>
|
|
<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td>
|
|
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
|
|
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
|
|
<td align="center"><a href="../../../../../more/index.htm">More</a></td>
|
|
</tr></table>
|
|
<hr>
|
|
<div class="spirit-nav">
|
|
<a accesskey="p" href="overload5.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_connect.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../async_initiate.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h4 class="title">
|
|
<a name="boost_asio.reference.async_connect.overload6"></a><a class="link" href="overload6.html" title="async_connect (6 of 6 overloads)">async_connect
|
|
(6 of 6 overloads)</a>
|
|
</h4></div></div></div>
|
|
<p>
|
|
Asynchronously 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>,
|
|
typename <a class="link" href="../IteratorConnectHandler.html" title="Iterator connect handler requirements">IteratorConnectHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>>
|
|
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_connect(
|
|
basic_socket< Protocol, Executor > & s,
|
|
Iterator begin,
|
|
Iterator end,
|
|
ConnectCondition connect_condition,
|
|
IteratorConnectHandler && handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
|
|
</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">async_connect</code>
|
|
member function, once for each endpoint in the sequence, until a connection
|
|
is successfully established.
|
|
</p>
|
|
<h6>
|
|
<a name="boost_asio.reference.async_connect.overload6.h0"></a>
|
|
<span class="phrase"><a name="boost_asio.reference.async_connect.overload6.parameters"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_connect.overload6.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& 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">handler</span></dt>
|
|
<dd>
|
|
<p>
|
|
The handler to be called when the connect operation completes. Copies
|
|
will be made of the handler as required. The function signature of
|
|
the handler must be:
|
|
</p>
|
|
<pre class="programlisting">void handler(
|
|
// Result of operation. if the sequence is empty, set to
|
|
// boost::asio::error::not_found. Otherwise, contains the
|
|
// error from the last connection attempt.
|
|
const boost::system::error_code& error,
|
|
|
|
// On success, an iterator denoting the successfully
|
|
// connected endpoint. Otherwise, the end iterator.
|
|
Iterator iterator
|
|
);
|
|
</pre>
|
|
<p>
|
|
Regardless of whether the asynchronous operation completes immediately
|
|
or not, the handler will not be invoked from within this function.
|
|
On immediate completion, invocation of the handler will be performed
|
|
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
</div>
|
|
<h6>
|
|
<a name="boost_asio.reference.async_connect.overload6.h1"></a>
|
|
<span class="phrase"><a name="boost_asio.reference.async_connect.overload6.example"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_connect.overload6.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& 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">boost::asio::connect</code> function as
|
|
follows:
|
|
</p>
|
|
<pre class="programlisting">tcp::resolver r(my_context);
|
|
tcp::resolver::query q("host", "service");
|
|
tcp::socket s(my_context);
|
|
|
|
// ...
|
|
|
|
r.async_resolve(q, resolve_handler);
|
|
|
|
// ...
|
|
|
|
void resolve_handler(
|
|
const boost::system::error_code& ec,
|
|
tcp::resolver::iterator i)
|
|
{
|
|
if (!ec)
|
|
{
|
|
tcp::resolver::iterator end;
|
|
boost::asio::async_connect(s, i, end,
|
|
my_connect_condition(),
|
|
connect_handler);
|
|
}
|
|
}
|
|
|
|
// ...
|
|
|
|
void connect_handler(
|
|
const boost::system::error_code& ec,
|
|
tcp::resolver::iterator i)
|
|
{
|
|
if (ec)
|
|
{
|
|
// An error occurred.
|
|
}
|
|
else
|
|
{
|
|
std::cout << "Connected to: " << i->endpoint() << std::endl;
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
|
<td align="left"></td>
|
|
<td align="right"><div class="copyright-footer">Copyright © 2003-2021 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>)
|
|
</p>
|
|
</div></td>
|
|
</tr></table>
|
|
<hr>
|
|
<div class="spirit-nav">
|
|
<a accesskey="p" href="overload5.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_connect.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../async_initiate.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
|
</div>
|
|
</body>
|
|
</html>
|