1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>async_connect (4 of 4 overloads)</title>
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.76.1">
<link rel="home" href="../../../boost_asio.html" title="Boost.Asio">
<link rel="up" href="../async_connect.html" title="async_connect">
<link rel="prev" href="overload3.html" title="async_connect (3 of 4 overloads)">
<link rel="next" href="../async_read.html" title="async_read">
</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="overload3.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_read.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.overload4"></a><a class="link" href="overload4.html" title="async_connect (4 of 4 overloads)">async_connect
(4 of 4 overloads)</a>
</h4></div></div></div>
<p>
Asynchronously establishes a socket connection by trying each endpoint
in a sequence.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
<span class="keyword">typename</span> <a class="link" href="../Protocol.html" title="Protocol requirements">Protocol</a><span class="special">,</span>
<span class="keyword">typename</span> <a class="link" href="../SocketService.html" title="Socket service requirements">SocketService</a><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">ConnectCondition</span><span class="special">,</span>
<span class="keyword">typename</span> <a class="link" href="../ComposedConnectHandler.html" title="Composed connect handler requirements">ComposedConnectHandler</a><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">async_connect</span><span class="special">(</span>
<span class="identifier">basic_socket</span><span class="special"><</span> <span class="identifier">Protocol</span><span class="special">,</span> <span class="identifier">SocketService</span> <span class="special">></span> <span class="special">&</span> <span class="identifier">s</span><span class="special">,</span>
<span class="identifier">Iterator</span> <span class="identifier">begin</span><span class="special">,</span>
<span class="identifier">Iterator</span> <span class="identifier">end</span><span class="special">,</span>
<span class="identifier">ConnectCondition</span> <span class="identifier">connect_condition</span><span class="special">,</span>
<span class="identifier">ComposedConnectHandler</span> <span class="identifier">handler</span><span class="special">);</span>
</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"><span class="identifier">async_connect</span></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.overload4.h0"></a>
<span><a name="boost_asio.reference.async_connect.overload4.parameters"></a></span><a class="link" href="overload4.html#boost_asio.reference.async_connect.overload4.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"><span class="identifier">Iterator</span> <span class="identifier">connect_condition</span><span class="special">(</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span>
<span class="identifier">Iterator</span> <span class="identifier">next</span><span class="special">);</span>
</pre>
<p>
The <code class="computeroutput"><span class="identifier">ec</span></code> parameter
contains the result from the most recent connect operation. Before
the first connection attempt, <code class="computeroutput"><span class="identifier">ec</span></code>
is always set to indicate success. The <code class="computeroutput"><span class="identifier">next</span></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.
</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"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
<span class="comment">// Result of operation. if the sequence is empty, set to</span>
<span class="comment">// boost::asio::error::not_found. Otherwise, contains the</span>
<span class="comment">// error from the last connection attempt.</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">error</span><span class="special">,</span>
<span class="comment">// On success, an iterator denoting the successfully</span>
<span class="comment">// connected endpoint. Otherwise, the end iterator.</span>
<span class="identifier">Iterator</span> <span class="identifier">iterator</span>
<span class="special">);</span>
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent
to using <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">post</span><span class="special">()</span></code>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_connect.overload4.h1"></a>
<span><a name="boost_asio.reference.async_connect.overload4.example"></a></span><a class="link" href="overload4.html#boost_asio.reference.async_connect.overload4.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"><span class="keyword">struct</span> <span class="identifier">my_connect_condition</span>
<span class="special">{</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">></span>
<span class="identifier">Iterator</span> <span class="keyword">operator</span><span class="special">()(</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span>
<span class="identifier">Iterator</span> <span class="identifier">next</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Error: "</span> <span class="special"><<</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Trying: "</span> <span class="special"><<</span> <span class="identifier">next</span><span class="special">-></span><span class="identifier">endpoint</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="keyword">return</span> <span class="identifier">next</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
</pre>
<p>
It would be used with the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">connect</span></code>
function as follows:
</p>
<pre class="programlisting"><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span> <span class="identifier">r</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">);</span>
<span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">query</span> <span class="identifier">q</span><span class="special">(</span><span class="string">"host"</span><span class="special">,</span> <span class="string">"service"</span><span class="special">);</span>
<span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">s</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">);</span>
<span class="comment">// ...</span>
<span class="identifier">r</span><span class="special">.</span><span class="identifier">async_resolve</span><span class="special">(</span><span class="identifier">q</span><span class="special">,</span> <span class="identifier">resolve_handler</span><span class="special">);</span>
<span class="comment">// ...</span>
<span class="keyword">void</span> <span class="identifier">resolve_handler</span><span class="special">(</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span>
<span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">i</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">end</span><span class="special">;</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">async_connect</span><span class="special">(</span><span class="identifier">s</span><span class="special">,</span> <span class="identifier">i</span><span class="special">,</span> <span class="identifier">end</span><span class="special">,</span>
<span class="identifier">my_connect_condition</span><span class="special">(),</span>
<span class="identifier">connect_handler</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="comment">// ...</span>
<span class="keyword">void</span> <span class="identifier">connect_handler</span><span class="special">(</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span>
<span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">i</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// An error occurred.</span>
<span class="special">}</span>
<span class="keyword">else</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Connected to: "</span> <span class="special"><<</span> <span class="identifier">i</span><span class="special">-></span><span class="identifier">endpoint</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span>
</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 © 2003-2012 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="overload3.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_read.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
