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<h1 class="topictitle1">Example: Send multicast datagrams </h1>
<div><p>This example enables a socket to send multicast datagrams.</p>
<div class="section"><div class="note"><span class="notetitle">Note:</span> By using the code examples, you agree to the terms of the <a href="codedisclaimer.htm">Code license and disclaimer information</a>.</div>
<pre>#include &lt;sys/types.h&gt;
#include &lt;sys/socket.h&gt;
#include &lt;arpa/inet.h&gt;
#include &lt;netinet/in.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
struct in_addr localInterface;
struct sockaddr_in groupSock;
int sd;
int datalen;
char databuf[1024];
int main (int argc, char *argv[])
{
/* ------------------------------------------------------------*/
/* */
/* Send Multicast Datagram code example. */
/* */
/* ------------------------------------------------------------*/
/*
* Create a datagram socket on which to send.
*/
sd = socket(AF_INET, SOCK_DGRAM, 0);
if (sd &lt; 0) {
perror("opening datagram socket");
exit(1);
}
/*
* Initialize the group sockaddr structure with a
* group address of 225.1.1.1 and port 5555.
*/
memset((char *) &amp;groupSock, 0, sizeof(groupSock));
groupSock.sin_family = AF_INET;
groupSock.sin_addr.s_addr = inet_addr("225.1.1.1");
groupSock.sin_port = htons(5555);
/*
* Disable loopback so you do not receive your own datagrams.
*/
{
char loopch=0;
if (setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP,
(char *)&amp;loopch, sizeof(loopch)) &lt; 0) {
perror("setting IP_MULTICAST_LOOP:");
close(sd);
exit(1);
}
}
/*
* Set local interface for outbound multicast datagrams.
* The IP address specified must be associated with a local,
* multicast-capable interface.
*/
localInterface.s_addr = inet_addr("9.5.1.1");
if (setsockopt(sd, IPPROTO_IP, IP_MULTICAST_IF,
(char *)&amp;localInterface,
sizeof(localInterface)) &lt; 0) {
perror("setting local interface");
exit(1);
}
/*
* Send a message to the multicast group specified by the
* groupSock sockaddr structure.
*/
datalen = 10;
if (sendto(sd, databuf, datalen, 0,
(struct sockaddr*)&amp;groupSock,
sizeof(groupSock)) &lt; 0)
{
perror("sending datagram message");
}
}</pre>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="xmulticast.htm" title="IP multicasting provides the capability for an application to send a single IP datagram that a group of hosts in a network can receive.">Examples: Use multicasting with AF_INET</a></div>
</div>
<div class="relref"><strong>Related reference</strong><br />
<div><a href="xmulticast.htm" title="IP multicasting provides the capability for an application to send a single IP datagram that a group of hosts in a network can receive.">Examples: Use multicasting with AF_INET</a></div>
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