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<title>Daytime.2 - A synchronous TCP daytime server</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.tutorial.tutdaytime2"></a><a class="link" href="tutdaytime2.html" title="Daytime.2 - A synchronous TCP daytime server">Daytime.2 - A synchronous
TCP daytime server</a>
</h3></div></div></div>
<p>
This tutorial program shows how to use asio to implement a server application
with TCP.
</p>
<pre class="programlisting"><span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span class="identifier">ctime</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span class="identifier">asio</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="keyword">using</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">;</span>
</pre>
<p>
We define the function <code class="computeroutput"><span class="identifier">make_daytime_string</span><span class="special">()</span></code> to create the string to be sent back to
the client. This function will be reused in all of our daytime server applications.
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">make_daytime_string</span><span class="special">()</span>
<span class="special">{</span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> <span class="comment">// For time_t, time and ctime;</span>
<span class="identifier">time_t</span> <span class="identifier">now</span> <span class="special">=</span> <span class="identifier">time</span><span class="special">(</span><span class="number">0</span><span class="special">);</span>
<span class="keyword">return</span> <span class="identifier">ctime</span><span class="special">(&amp;</span><span class="identifier">now</span><span class="special">);</span>
<span class="special">}</span>
<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>
<span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span> <span class="identifier">io_context</span><span class="special">;</span>
</pre>
<p>
A <a class="link" href="../reference/ip__tcp/acceptor.html" title="ip::tcp::acceptor">ip::tcp::acceptor</a>
object needs to be created to listen for new connections. It is initialised
to listen on TCP port 13, for IP version 4.
</p>
<pre class="programlisting"> <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">acceptor</span> <span class="identifier">acceptor</span><span class="special">(</span><span class="identifier">io_context</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>
</pre>
<p>
This is an iterative server, which means that it will handle one connection
at a time. Create a socket that will represent the connection to the client,
and then wait for a connection.
</p>
<pre class="programlisting"> <span class="keyword">for</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">io_context</span><span class="special">);</span>
<span class="identifier">acceptor</span><span class="special">.</span><span class="identifier">accept</span><span class="special">(</span><span class="identifier">socket</span><span class="special">);</span>
</pre>
<p>
A client is accessing our service. Determine the current time and transfer
this information to the client.
</p>
<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>
<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>
<span class="identifier">asio</span><span class="special">::</span><span class="identifier">write</span><span class="special">(</span><span class="identifier">socket</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">ignored_error</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">}</span>
</pre>
<p>
Finally, handle any exceptions.
</p>
<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>
<span class="special">{</span>
<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>
<span class="special">}</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
See the <a class="link" href="tutdaytime2/src.html" title="Source listing for Daytime.2">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="tutdaytime1.html" title="Daytime.1 - A synchronous TCP daytime client">Daytime.1 - A synchronous
TCP daytime client</a>
</p>
<p>
Next: <a class="link" href="tutdaytime3.html" title="Daytime.3 - An asynchronous TCP daytime server">Daytime.3 - An asynchronous
TCP daytime server</a>
</p>
</div>
<div class="copyright-footer">Copyright © 2003-2023 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>)
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