1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>connect (11 of 12 overloads)</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../connect.html" title="connect"> 9<link rel="prev" href="overload10.html" title="connect (10 of 12 overloads)"> 10<link rel="next" href="overload12.html" title="connect (12 of 12 overloads)"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="overload10.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="overload12.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_asio.reference.connect.overload11"></a><a class="link" href="overload11.html" title="connect (11 of 12 overloads)">connect (11 28 of 12 overloads)</a> 29</h4></div></div></div> 30<p> 31 Establishes a socket connection by trying each endpoint in a sequence. 32 </p> 33<pre class="programlisting">template< 34 typename <a class="link" href="../Protocol.html" title="Protocol requirements">Protocol</a>, 35 typename <a class="link" href="../Executor1.html" title="Executor requirements">Executor</a>, 36 typename Iterator, 37 typename <a class="link" href="../ConnectCondition.html" title="Connect condition requirements">ConnectCondition</a>> 38Iterator connect( 39 basic_socket< Protocol, Executor > & s, 40 Iterator begin, 41 Iterator end, 42 ConnectCondition connect_condition); 43</pre> 44<p> 45 This function attempts to connect a socket to one of a sequence of endpoints. 46 It does this by repeated calls to the socket's <code class="computeroutput">connect</code> member 47 function, once for each endpoint in the sequence, until a connection is 48 successfully established. 49 </p> 50<h6> 51<a name="boost_asio.reference.connect.overload11.h0"></a> 52 <span class="phrase"><a name="boost_asio.reference.connect.overload11.parameters"></a></span><a class="link" href="overload11.html#boost_asio.reference.connect.overload11.parameters">Parameters</a> 53 </h6> 54<div class="variablelist"> 55<p class="title"><b></b></p> 56<dl class="variablelist"> 57<dt><span class="term">s</span></dt> 58<dd><p> 59 The socket to be connected. If the socket is already open, it will 60 be closed. 61 </p></dd> 62<dt><span class="term">begin</span></dt> 63<dd><p> 64 An iterator pointing to the start of a sequence of endpoints. 65 </p></dd> 66<dt><span class="term">end</span></dt> 67<dd><p> 68 An iterator pointing to the end of a sequence of endpoints. 69 </p></dd> 70<dt><span class="term">connect_condition</span></dt> 71<dd> 72<p> 73 A function object that is called prior to each connection attempt. 74 The signature of the function object must be: 75</p> 76<pre class="programlisting">bool connect_condition( 77 const boost::system::error_code& ec, 78 const typename Protocol::endpoint& next); 79</pre> 80<p> 81 The <code class="computeroutput">ec</code> parameter contains the result from the most recent 82 connect operation. Before the first connection attempt, <code class="computeroutput">ec</code> 83 is always set to indicate success. The <code class="computeroutput">next</code> parameter 84 is the next endpoint to be tried. The function object should return 85 true if the next endpoint should be tried, and false if it should 86 be skipped. 87 </p> 88</dd> 89</dl> 90</div> 91<h6> 92<a name="boost_asio.reference.connect.overload11.h1"></a> 93 <span class="phrase"><a name="boost_asio.reference.connect.overload11.return_value"></a></span><a class="link" href="overload11.html#boost_asio.reference.connect.overload11.return_value">Return Value</a> 94 </h6> 95<p> 96 An iterator denoting the successfully connected endpoint. 97 </p> 98<h6> 99<a name="boost_asio.reference.connect.overload11.h2"></a> 100 <span class="phrase"><a name="boost_asio.reference.connect.overload11.exceptions"></a></span><a class="link" href="overload11.html#boost_asio.reference.connect.overload11.exceptions">Exceptions</a> 101 </h6> 102<div class="variablelist"> 103<p class="title"><b></b></p> 104<dl class="variablelist"> 105<dt><span class="term">boost::system::system_error</span></dt> 106<dd><p> 107 Thrown on failure. If the sequence is empty, the associated <code class="computeroutput">error_code</code> 108 is <code class="computeroutput">boost::asio::error::not_found</code>. Otherwise, contains 109 the error from the last connection attempt. 110 </p></dd> 111</dl> 112</div> 113<h6> 114<a name="boost_asio.reference.connect.overload11.h3"></a> 115 <span class="phrase"><a name="boost_asio.reference.connect.overload11.example"></a></span><a class="link" href="overload11.html#boost_asio.reference.connect.overload11.example">Example</a> 116 </h6> 117<p> 118 The following connect condition function object can be used to output information 119 about the individual connection attempts: 120 </p> 121<pre class="programlisting">struct my_connect_condition 122{ 123 bool operator()( 124 const boost::system::error_code& ec, 125 const::tcp::endpoint& next) 126 { 127 if (ec) std::cout << "Error: " << ec.message() << std::endl; 128 std::cout << "Trying: " << next << std::endl; 129 return true; 130 } 131}; 132</pre> 133<p> 134 It would be used with the <code class="computeroutput">boost::asio::connect</code> function as 135 follows: 136 </p> 137<pre class="programlisting">tcp::resolver r(my_context); 138tcp::resolver::query q("host", "service"); 139tcp::resolver::results_type e = r.resolve(q); 140tcp::socket s(my_context); 141tcp::resolver::results_type::iterator i = boost::asio::connect( 142 s, e.begin(), e.end(), my_connect_condition()); 143std::cout << "Connected to: " << i->endpoint() << std::endl; 144</pre> 145</div> 146<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 147<td align="left"></td> 148<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 149 Kohlhoff<p> 150 Distributed under the Boost Software License, Version 1.0. (See accompanying 151 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>) 152 </p> 153</div></td> 154</tr></table> 155<hr> 156<div class="spirit-nav"> 157<a accesskey="p" href="overload10.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="overload12.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 158</div> 159</body> 160</html> 161
