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<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>connect (6 of 8 overloads)</title> <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> <link rel="up" href="../connect.html" title="connect"> <link rel="prev" href="overload5.html" title="connect (5 of 8 overloads)"> <link rel="next" href="overload7.html" title="connect (7 of 8 overloads)"> </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="../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="overload7.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.connect.overload6"></a><a class="link" href="overload6.html" title="connect (6 of 8 overloads)">connect (6 of 8 overloads)</a> </h4></div></div></div> Establishes a socket connection by trying each endpoint in a sequence. <pre class="programlisting">template< typename <a class="link" href="../Protocol.html" title="Protocol requirements">Protocol</a>, typename <a class="link" href="../SocketService.html" title="Socket service requirements">SocketService</a>, typename Iterator, typename ConnectCondition> Iterator connect( basic_socket< Protocol, SocketService > & s, Iterator begin, ConnectCondition connect_condition, boost::system::error_code & ec); </pre> 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. <h6> <a name="boost_asio.reference.connect.overload6.h0"></a> <a name="boost_asio.reference.connect.overload6.parameters"></a><a class="link" href="overload6.html#boost_asio.reference.connect.overload6.parameters">Parameters</a> </h6> <div class="variablelist"> <dl class="variablelist"> <dt>s</dt> <dd> The socket to be connected. If the socket is already open, it will be closed. </dd> <dt>begin</dt> <dd> An iterator pointing to the start of a sequence of endpoints. </dd> <dt>connect_condition</dt> <dd> A function object that is called prior to each connection attempt. The signature of the function object must be: <pre class="programlisting">Iterator connect_condition( const boost::system::error_code& ec, Iterator next); </pre> 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 an iterator pointing to the next endpoint to be tried. The function object should return the next iterator, but is permitted to return a different iterator so that endpoints may be skipped. The implementation guarantees that the function object will never be called with the end iterator. </dd> <dt>ec</dt> <dd> 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. </dd> </dl> </div> <h6> <a name="boost_asio.reference.connect.overload6.h1"></a> <a name="boost_asio.reference.connect.overload6.return_value"></a><a class="link" href="overload6.html#boost_asio.reference.connect.overload6.return_value">Return Value</a> </h6> On success, an iterator denoting the successfully connected endpoint. Otherwise, the end iterator. <h6> <a name="boost_asio.reference.connect.overload6.h2"></a> <a name="boost_asio.reference.connect.overload6.remarks"></a><a class="link" href="overload6.html#boost_asio.reference.connect.overload6.remarks">Remarks</a> </h6> This overload assumes that a default constructed object of type <code class="computeroutput">Iterator</code> represents the end of the sequence. This is a valid assumption for iterator types such as <code class="computeroutput">boost::asio::ip::tcp::resolver::iterator</code>. <h6> <a name="boost_asio.reference.connect.overload6.h3"></a> <a name="boost_asio.reference.connect.overload6.example"></a><a class="link" href="overload6.html#boost_asio.reference.connect.overload6.example">Example</a> </h6> The following connect condition function object can be used to output information about the individual connection attempts: <pre class="programlisting">struct my_connect_condition { template <typename Iterator> Iterator operator()( const boost::system::error_code& ec, Iterator next) { if (ec) std::cout << "Error: " << ec.message() << std::endl; std::cout << "Trying: " << next->endpoint() << std::endl; return next; } }; </pre> It would be used with the <code class="computeroutput">boost::asio::connect</code> function as follows: <pre class="programlisting">tcp::resolver r(io_service); tcp::resolver::query q("host", "service"); tcp::socket s(io_service); boost::system::error_code ec; tcp::resolver::iterator i = boost::asio::connect( s, r.resolve(q), my_connect_condition(), ec); 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 © 2003-2014 Christopher M. Kohlhoff 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>) </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="../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="overload7.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>