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  4. <title>Daytime.5 - A synchronous UDP daytime server</title>
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  13. <table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../asio.png"></td></tr></table>
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  16. <a accesskey="p" href="tutdaytime4/src.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial.html"><img src="../../up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../home.png" alt="Home"></a><a accesskey="n" href="tutdaytime5/src.html"><img src="../../next.png" alt="Next"></a>
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  18. <div class="section" lang="en">
    19. 

  19. <div class="titlepage"><div><div><h3 class="title">
    20. 

  20. <a name="asio.tutorial.tutdaytime5"></a><a class="link" href="tutdaytime5.html" title="Daytime.5 - A synchronous UDP daytime server">Daytime.5 - A synchronous
    21. 

  21.       UDP daytime server</a>
    22. 

  22. </h3></div></div></div>
    23. 

  23. <p>
    24. 

  24.         This tutorial program shows how to use asio to implement a server application
    25. 

  25.         with UDP.
    26. 

  26.       </p>
    27. 

  27. <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
    28. 

  28. <span class="special">{</span>
    29. 

  29.   <span class="keyword">try</span>
    30. 

  30.   <span class="special">{</span>
    31. 

  31.     <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>
    32. 

  32. </pre>
    33. 

  33. <p>
    34. 

  34.         Create an <a class="link" href="../reference/ip__udp/socket.html" title="ip::udp::socket">ip::udp::socket</a>
    35. 

  35.         object to receive requests on UDP port 13.
    36. 

  36.       </p>
    37. 

  37. <pre class="programlisting">    <span class="identifier">udp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">socket</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">,</span> <span class="identifier">udp</span><span class="special">::</span><span class="identifier">endpoint</span><span class="special">(</span><span class="identifier">udp</span><span class="special">::</span><span class="identifier">v4</span><span class="special">(),</span> <span class="number">13</span><span class="special">));</span>
    38. 

  38. </pre>
    39. 

  39. <p>
    40. 

  40.         Wait for a client to initiate contact with us. The remote_endpoint object
    41. 

  41.         will be populated by <a class="link" href="../reference/basic_datagram_socket/receive_from.html" title="basic_datagram_socket::receive_from">ip::udp::socket::receive_from()</a>.
    42. 

  42.       </p>
    43. 

  43. <pre class="programlisting">    <span class="keyword">for</span> <span class="special">(;;)</span>
    44. 

  44.     <span class="special">{</span>
    45. 

  45.       <span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">,</span> <span class="number">1</span><span class="special">&gt;</span> <span class="identifier">recv_buf</span><span class="special">;</span>
    46. 

  46.       <span class="identifier">udp</span><span class="special">::</span><span class="identifier">endpoint</span> <span class="identifier">remote_endpoint</span><span class="special">;</span>
    47. 

  47.       <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">error</span><span class="special">;</span>
    48. 

  48.       <span class="identifier">socket</span><span class="special">.</span><span class="identifier">receive_from</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">recv_buf</span><span class="special">),</span>
    49. 

  49.           <span class="identifier">remote_endpoint</span><span class="special">,</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">error</span><span class="special">);</span>
    50. 

  50. 

  51.       <span class="keyword">if</span> <span class="special">(</span><span class="identifier">error</span> <span class="special">&amp;&amp;</span> <span class="identifier">error</span> <span class="special">!=</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">message_size</span><span class="special">)</span>
    52. 

  52.         <span class="keyword">throw</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">system_error</span><span class="special">(</span><span class="identifier">error</span><span class="special">);</span>
    53. 

  53. </pre>
    54. 

  54. <p>
    55. 

  55.         Determine what we are going to send back to the client.
    56. 

  56.       </p>
    57. 

  57. <pre class="programlisting">      <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="identifier">make_daytime_string</span><span class="special">();</span>
    58. 

  58. </pre>
    59. 

  59. <p>
    60. 

  60.         Send the response to the remote_endpoint.
    61. 

  61.       </p>
    62. 

  62. <pre class="programlisting">      <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">ignored_error</span><span class="special">;</span>
    63. 

  63.       <span class="identifier">socket</span><span class="special">.</span><span class="identifier">send_to</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>
    64. 

  64.           <span class="identifier">remote_endpoint</span><span class="special">,</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">ignored_error</span><span class="special">);</span>
    65. 

  65.     <span class="special">}</span>
    66. 

  66.   <span class="special">}</span>
    67. 

  67. </pre>
    68. 

  68. <p>
    69. 

  69.         Finally, handle any exceptions.
    70. 

  70.       </p>
    71. 

  71. <pre class="programlisting">  <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">&amp;</span> <span class="identifier">e</span><span class="special">)</span>
    72. 

  72.   <span class="special">{</span>
    73. 

  73.     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special">&lt;&lt;</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    74. 

  74.   <span class="special">}</span>
    75. 

  75. 

  76.   <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
    77. 

  77. <span class="special">}</span>
    78. 

  78. </pre>
    79. 

  79. <p>
    80. 

  80.         See the <a class="link" href="tutdaytime5/src.html" title="Source listing for Daytime.5">full source listing</a>
    81. 

  81.       </p>
    82. 

  82. <p>
    83. 

  83.         Return to the <a class="link" href="../tutorial.html" title="Tutorial">tutorial index</a>
    84. 

  84.       </p>
    85. 

  85. <p>
    86. 

  86.         Previous: <a class="link" href="tutdaytime4.html" title="Daytime.4 - A synchronous UDP daytime client">Daytime.4 - A synchronous
    87. 

  87.         UDP daytime client</a>
    88. 

  88.       </p>
    89. 

  89. <p>
    90. 

  90.         Next: <a class="link" href="tutdaytime6.html" title="Daytime.6 - An asynchronous UDP daytime server">Daytime.6 - An asynchronous
    91. 

  91.         UDP daytime server</a>
    92. 

  92.       </p>
    93. 

  93. </div>
    94. 

  94. <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
    95. 

  95. <td align="left"></td>
    96. 

  96. <td align="right"><div class="copyright-footer">Copyright &#169; 2003 - 2010 Christopher M. Kohlhoff<p>
    97. 

  97.         Distributed under the Boost Software License, Version 1.0. (See accompanying
    98. 

  98.         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>)
    99. 

  99.       </p>
    100. 

  100. </div></td>
    101. 

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    102. 

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