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<META NAME="Author" CONTENT="James CE Johnson">
<TITLE>ACE Tutorial 009</TITLE>
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<CENTER><B><FONT SIZE=+2>ACE Tutorial 009</FONT></B></CENTER>
<CENTER><B><FONT SIZE=+2>Sending and receiving datagrams again</FONT></B></CENTER>
<P>
<HR WIDTH="100%">
<P>Let's take a look at our new <A HREF="server.cpp">server.cpp</A> where
we add in just a bit of code to examine the datagram contents before responding.
<P>
<HR WIDTH="100%"><TT></TT>
<P><TT>/*</TT>
<BR><TT> The actual datagram operations here are exactly the
same as those used in</TT>
<BR><TT> the previous tutorial. What we've added is some
logic that will prevent</TT>
<BR><TT> this server from responding to just any old datagram.
I'll limit my</TT>
<BR><TT> comments to those pieces of code.</TT>
<BR><TT> */</TT><TT></TT>
<P><TT>#include "ace/SOCK_Dgram.h"</TT>
<BR><TT>#include "ace/INET_Addr.h"</TT><TT></TT>
<P><TT>static const u_short PORT = ACE_DEFAULT_SERVER_PORT;</TT><TT></TT>
<P><TT>/*</TT>
<BR><TT> In order to be more selective, our server will be
started with a</TT>
<BR><TT> "signature". If none is given, we'll use the
one here instead.</TT>
<BR><TT> */</TT>
<BR><TT>static const char *default_signature = "Hello World!";</TT><TT></TT>
<P><TT>int main (int argc, char *argv[])</TT>
<BR><TT>{</TT>
<BR><TT> ACE_INET_Addr local (PORT);</TT>
<BR><TT> ACE_SOCK_Dgram dgram;</TT><TT></TT>
<P><TT> if (dgram.open (local) == -1)</TT>
<BR><TT> {</TT>
<BR><TT> ACE_ERROR_RETURN ((LM_ERROR, "%p\n", "open"),
-1);</TT>
<BR><TT> }</TT><TT></TT>
<P><TT> char buf[512];</TT>
<BR><TT> ACE_INET_Addr remote;</TT><TT></TT>
<P><TT> while (dgram.recv (buf, sizeof (buf), remote) != -1)</TT>
<BR><TT> {</TT>
<BR><TT> /*</TT>
<BR><TT> What did the client say?</TT>
<BR><TT> */</TT>
<BR><TT> ACE_DEBUG ((LM_DEBUG, "(%P|%t) Received (%s)
from (%s)\n", buf, remote.get_host_name ()));</TT><TT></TT>
<P><TT> /*</TT>
<BR><TT> Use a simple string-op to
decide if the client is one of our own. Of</TT>
<BR><TT> course, you could have sent
numeric values or even a struct of data. For</TT>
<BR><TT> this simple exercise, however,
strings are just fine.</TT>
<BR><TT> */</TT>
<BR><TT> if (ACE_OS::strcmp (buf, argc > 1 ? argv[1]
: default_signature))</TT>
<BR><TT> {</TT>
<BR><TT> /*</TT>
<BR><TT> If the client
didn't say something we like then log it and move on.</TT>
<BR><TT> */</TT>
<BR><TT> ACE_DEBUG ((LM_DEBUG,</TT>
<BR><TT>
"(%P|%t) Client query does not match our signature (%s). Response
not sent.\n",</TT>
<BR><TT>
argc > 1 ? argv[1] : default_signature));</TT>
<BR><TT> }</TT>
<BR><TT> else</TT>
<BR><TT> {</TT>
<BR><TT> /*</TT>
<BR><TT> As before, we
respond to the client's query.</TT>
<BR><TT> */</TT><TT></TT>
<P><TT> ACE_INET_Addr local ((u_short) 0);</TT>
<BR><TT> ACE_SOCK_Dgram client;</TT>
<BR><TT> if (client.open (local) == -1)</TT>
<BR><TT> {</TT>
<BR><TT> ACE_ERROR_RETURN
((LM_ERROR, "%p\n", "response open"), -1);</TT>
<BR><TT> }</TT><TT></TT>
<P><TT> sprintf (buf, "I am here");</TT>
<BR><TT> if (client.send (buf, strlen (buf)
+ 1, remote) == -1)</TT>
<BR><TT> {</TT>
<BR><TT> ACE_ERROR_RETURN
((LM_ERROR, "%p\n", "response send"), -1);</TT>
<BR><TT> }</TT>
<BR><TT> }</TT>
<BR><TT> }</TT><TT></TT>
<P><TT> return (0);</TT>
<BR><TT>}</TT><TT></TT>
<P>
<HR WIDTH="100%">
<P>Let's move on and see what changes the clients require...
<P>
<HR WIDTH="100%">
<CENTER>[<A HREF="..">Tutorial Index</A>] [<A HREF="page03.html">Continue
This Tutorial</A>]</CENTER>
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