1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
|
// $Id$
#include "ace/SOCK_Dgram.h"
#include "ace/INET_Addr.h"
/*
Once again, we use the default server port. In a "real" system,
the server's port (or ports) would be published in some way so
that clients would know where to "look". We could even add entries
to the operating system's services file and use a service name
instead of a number. We'll come back to that in some other tutorial
though. For now, let's stay simple.
*/
static const u_short PORT = ACE_DEFAULT_SERVER_PORT;
/*
Our goal here is to develop a client that can send a datagram to
a server running on a known host. We'll use a command-line argument
to specify the hostname instead of hard-coding it.
*/
int main(int argc,char *argv[] )
{
/*
All datagrams have to have a point of origin. Since we intend to
transmit instead of receive, we initialize an address with zero
and let the OS choose a port for us. We could have chosen our
own value between 1025 and 65535 as long as it isn't already in use.
*/
ACE_INET_Addr local((u_short)0);
/*
And here is our datagram object.
*/
ACE_SOCK_Dgram dgram;
/*
Notice that this looks a lot like the server application. There's
no difference in creating server datagrams an client datagrams.
You can even use a zero-constructed address for your server datagram
as long as you tell the client where you're listening (eg -- by writting
into a file or some such).
*/
if( dgram.open(local) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "%p\n", "datagram open"),-1);
}
/*
Yep. We've seen this before too...
*/
char buf[512];
/*
Ok, now we're doing something different.
*/
sprintf(buf, "Hello World!");
/*
Just like sending a telegram, we have to address our datagram.
Here, we create an address object at the desired port on the
chosen host. To keep us from crashing, we'll provide a default
host name if we aren't given one.
*/
ACE_INET_Addr remote(PORT, argc > 1 ? argv[1] : "localhost" );
ACE_DEBUG ((LM_DEBUG, "(%P|%t) Sending (%s) to the server.\n",buf));
/*
Now we send our buffer of stuff to the remote address. This is
just exactly what the server did after receiving a client message.
Datagrams are rather orthogonal that way: they don't generally make
much of a fuss about being either client or server.
*/
if( dgram.send(buf,strlen(buf)+1,remote) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "%p\n", "send"),-1);
}
/*
Now we've turned around and put ourselves into "server mode" by
invoking the recv() method. We now our server is going to send
us something, so we hang out here and wait for it. Because we
know datagrams are unreliable, there is a chance that the server
will respond but we won't hear. You might consider providing a
timeout on the recv() in that case. If recv() fails due to timeout
it will return -1 and you can then resend your query and attempt
the recv() again.
Like the server application, we have to give the recv() an
uninitialized addr object so that we can find out who is talking
back to us.
*/
if( dgram.recv(buf,sizeof(buf),remote) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "%p\n", "recv"),-1);
}
/*
Find out what the server had to say.
*/
ACE_DEBUG ((LM_DEBUG, "(%P|%t) The server said: %s\n",buf));
/*
Using the "remote" object instance, find out where the server lives.
We could then save this address and use directed datagrams to chat
with the server for a while.
*/
ACE_DEBUG ((LM_DEBUG, "(%P|%t) The server can be found at: (%s:%d)\n",
remote.get_host_name(), PORT ));
return(0);
}
|
