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| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_asio.tutorial.tutdaytime3"></a><a class="link" href="tutdaytime3.html" title="Daytime.3 - An asynchronous TCP daytime server">Daytime.3 - An asynchronous |
| TCP daytime server</a> |
| </h3></div></div></div> |
| <a name="boost_asio.tutorial.tutdaytime3.the_main___function"></a><h5> |
| <a name="id795896"></a> |
| <a class="link" href="tutdaytime3.html#boost_asio.tutorial.tutdaytime3.the_main___function">The main() |
| function</a> |
| </h5> |
| <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">try</span> |
| <span class="special">{</span> |
| </pre> |
| <p> |
| We need to create a server object to accept incoming client connections. |
| The <a class="link" href="../reference/io_service.html" title="io_service">io_service</a> object |
| provides I/O services, such as sockets, that the server object will use. |
| </p> |
| <pre class="programlisting"> <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="identifier">io_service</span><span class="special">;</span> |
| <span class="identifier">tcp_server</span> <span class="identifier">server</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">);</span> |
| </pre> |
| <p> |
| Run the <a class="link" href="../reference/io_service.html" title="io_service">io_service</a> |
| object so that it will perform asynchronous operations on your behalf. |
| </p> |
| <pre class="programlisting"> <span class="identifier">io_service</span><span class="special">.</span><span class="identifier">run</span><span class="special">();</span> |
| <span class="special">}</span> |
| <span class="keyword">catch</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">exception</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</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="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <a name="boost_asio.tutorial.tutdaytime3.the_tcp_server_class"></a><h5> |
| <a name="id796207"></a> |
| <a class="link" href="tutdaytime3.html#boost_asio.tutorial.tutdaytime3.the_tcp_server_class">The |
| tcp_server class</a> |
| </h5> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">tcp_server</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| </pre> |
| <p> |
| The constructor initialises an acceptor to listen on TCP port 13. |
| </p> |
| <pre class="programlisting"> <span class="identifier">tcp_server</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">io_service</span><span class="special">&</span> <span class="identifier">io_service</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">acceptor_</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">endpoint</span><span class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">v4</span><span class="special">(),</span> <span class="number">13</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="identifier">start_accept</span><span class="special">();</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">private</span><span class="special">:</span> |
| </pre> |
| <p> |
| The function <code class="computeroutput"><span class="identifier">start_accept</span><span class="special">()</span></code> creates a socket and initiates an asynchronous |
| accept operation to wait for a new connection. |
| </p> |
| <pre class="programlisting"> <span class="keyword">void</span> <span class="identifier">start_accept</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">tcp_connection</span><span class="special">::</span><span class="identifier">pointer</span> <span class="identifier">new_connection</span> <span class="special">=</span> |
| <span class="identifier">tcp_connection</span><span class="special">::</span><span class="identifier">create</span><span class="special">(</span><span class="identifier">acceptor_</span><span class="special">.</span><span class="identifier">io_service</span><span class="special">());</span> |
| |
| <span class="identifier">acceptor_</span><span class="special">.</span><span class="identifier">async_accept</span><span class="special">(</span><span class="identifier">new_connection</span><span class="special">-></span><span class="identifier">socket</span><span class="special">(),</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&</span><span class="identifier">tcp_server</span><span class="special">::</span><span class="identifier">handle_accept</span><span class="special">,</span> <span class="keyword">this</span><span class="special">,</span> <span class="identifier">new_connection</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">placeholders</span><span class="special">::</span><span class="identifier">error</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The function <code class="computeroutput"><span class="identifier">handle_accept</span><span class="special">()</span></code> is called when the asynchronous accept |
| operation initiated by <code class="computeroutput"><span class="identifier">start_accept</span><span class="special">()</span></code> finishes. It services the client request, |
| and then calls <code class="computeroutput"><span class="identifier">start_accept</span><span class="special">()</span></code> to initiate the next accept operation. |
| </p> |
| <pre class="programlisting"> <span class="keyword">void</span> <span class="identifier">handle_accept</span><span class="special">(</span><span class="identifier">tcp_connection</span><span class="special">::</span><span class="identifier">pointer</span> <span class="identifier">new_connection</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">error</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">error</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">new_connection</span><span class="special">-></span><span class="identifier">start</span><span class="special">();</span> |
| <span class="identifier">start_accept</span><span class="special">();</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| </pre> |
| <a name="boost_asio.tutorial.tutdaytime3.the_tcp_connection_class"></a><h5> |
| <a name="id796871"></a> |
| <a class="link" href="tutdaytime3.html#boost_asio.tutorial.tutdaytime3.the_tcp_connection_class">The |
| tcp_connection class</a> |
| </h5> |
| <p> |
| We will use <code class="computeroutput"><span class="identifier">shared_ptr</span></code> and |
| <code class="computeroutput"><span class="identifier">enable_shared_from_this</span></code> because |
| we want to keep the <code class="computeroutput"><span class="identifier">tcp_connection</span></code> |
| object alive as long as there is an operation that refers to it. |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">tcp_connection</span> |
| <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">enable_shared_from_this</span><span class="special"><</span><span class="identifier">tcp_connection</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special"><</span><span class="identifier">tcp_connection</span><span class="special">></span> <span class="identifier">pointer</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">pointer</span> <span class="identifier">create</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">io_service</span><span class="special">&</span> <span class="identifier">io_service</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">pointer</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">tcp_connection</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">));</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&</span> <span class="identifier">socket</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">socket_</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| In the function <code class="computeroutput"><span class="identifier">start</span><span class="special">()</span></code>, |
| we call boost::asio::async_write() to serve the data to the client. Note |
| that we are using boost::asio::async_write(), rather than <a class="link" href="../reference/basic_stream_socket/async_write_some.html" title="basic_stream_socket::async_write_some">ip::tcp::socket::async_write_some()</a>, |
| to ensure that the entire block of data is sent. |
| </p> |
| <pre class="programlisting"> <span class="keyword">void</span> <span class="identifier">start</span><span class="special">()</span> |
| <span class="special">{</span> |
| </pre> |
| <p> |
| The data to be sent is stored in the class member <code class="computeroutput"><span class="identifier">message_</span></code> |
| as we need to keep the data valid until the asynchronous operation is complete. |
| </p> |
| <pre class="programlisting"> <span class="identifier">message_</span> <span class="special">=</span> <span class="identifier">make_daytime_string</span><span class="special">();</span> |
| </pre> |
| <p> |
| When initiating the asynchronous operation, and if using boost::bind(), you |
| must specify only the arguments that match the handler's parameter list. |
| In this program, both of the argument placeholders (boost::asio::placeholders::error |
| and boost::asio::placeholders::bytes_transferred) could potentially have |
| been removed, since they are not being used in <code class="computeroutput"><span class="identifier">handle_write</span><span class="special">()</span></code>. |
| </p> |
| <pre class="programlisting"> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">async_write</span><span class="special">(</span><span class="identifier">socket_</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">buffer</span><span class="special">(</span><span class="identifier">message_</span><span class="special">),</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&</span><span class="identifier">tcp_connection</span><span class="special">::</span><span class="identifier">handle_write</span><span class="special">,</span> <span class="identifier">shared_from_this</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">placeholders</span><span class="special">::</span><span class="identifier">error</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">placeholders</span><span class="special">::</span><span class="identifier">bytes_transferred</span><span class="special">));</span> |
| </pre> |
| <p> |
| Any further actions for this client connection are now the responsibility |
| of <code class="computeroutput"><span class="identifier">handle_write</span><span class="special">()</span></code>. |
| </p> |
| <pre class="programlisting"> <span class="special">}</span> |
| |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">tcp_connection</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">io_service</span><span class="special">&</span> <span class="identifier">io_service</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">socket_</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">void</span> <span class="identifier">handle_write</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="comment">/*error*/</span><span class="special">,</span> |
| <span class="identifier">size_t</span> <span class="comment">/*bytes_transferred*/</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">socket_</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">message_</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <a name="boost_asio.tutorial.tutdaytime3.removing_unused_handler_parameters"></a><h5> |
| <a name="id797793"></a> |
| <a class="link" href="tutdaytime3.html#boost_asio.tutorial.tutdaytime3.removing_unused_handler_parameters">Removing |
| unused handler parameters</a> |
| </h5> |
| <p> |
| You may have noticed that the <code class="computeroutput"><span class="identifier">error</span></code>, |
| and <code class="computeroutput"><span class="identifier">bytes_transferred</span></code> parameters |
| are not used in the body of the <code class="computeroutput"><span class="identifier">handle_write</span><span class="special">()</span></code> function. If parameters are not needed, |
| it is possible to remove them from the function so that it looks like: |
| </p> |
| <pre class="programlisting"> <span class="keyword">void</span> <span class="identifier">handle_write</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The boost::asio::async_write() call used to initiate the call can then be |
| changed to just: |
| </p> |
| <pre class="programlisting"> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">async_write</span><span class="special">(</span><span class="identifier">socket_</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">buffer</span><span class="special">(</span><span class="identifier">message_</span><span class="special">),</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&</span><span class="identifier">tcp_connection</span><span class="special">::</span><span class="identifier">handle_write</span><span class="special">,</span> <span class="identifier">shared_from_this</span><span class="special">()));</span> |
| </pre> |
| <p> |
| See the <a class="link" href="tutdaytime3/src.html" title="Source listing for Daytime.3">full source listing</a> |
| </p> |
| <p> |
| Return to the <a class="link" href="../tutorial.html" title="Tutorial">tutorial index</a> |
| </p> |
| <p> |
| Previous: <a class="link" href="tutdaytime2.html" title="Daytime.2 - A synchronous TCP daytime server">Daytime.2 - A synchronous |
| TCP daytime server</a> |
| </p> |
| <p> |
| Next: <a class="link" href="tutdaytime4.html" title="Daytime.4 - A synchronous UDP daytime client">Daytime.4 - A synchronous |
| UDP daytime client</a> |
| </p> |
| </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 - 2010 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> |
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