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