tutdaytime2.html
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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">#include <ctime>
#include <iostream>
#include <string>
#include <asio.hpp>
using asio::ip::tcp;
</pre>
<p>
We define the function <code class="computeroutput">make_daytime_string()</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">std::string make_daytime_string()
{
using namespace std; // For time_t, time and ctime;
time_t now = time(0);
return ctime(&now);
}
int main()
{
try
{
asio::io_context io_context;
</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"> tcp::acceptor acceptor(io_context, tcp::endpoint(tcp::v4(), 13));
</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"> for (;;)
{
tcp::socket socket(io_context);
acceptor.accept(socket);
</pre>
<p>
A client is accessing our service. Determine the current time and transfer
this information to the client.
</p>
<pre class="programlisting"> std::string message = make_daytime_string();
asio::error_code ignored_error;
asio::write(socket, asio::buffer(message), ignored_error);
}
}
</pre>
<p>
Finally, handle any exceptions.
</p>
<pre class="programlisting"> catch (std::exception& e)
{
std::cerr << e.what() << std::endl;
}
return 0;
}
</pre>
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See the <a class="link" href="tutdaytime2/src.html" title="Source listing for Daytime.2">full source listing</a>
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Previous: <a class="link" href="tutdaytime1.html" title="Daytime.1 - A synchronous TCP daytime client">Daytime.1 - A synchronous
TCP daytime client</a>
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<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>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 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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