Multicast sender/listener

Dejo un ejemplo de como hacer multicast en C/Linux.


sender.c - el envío de mensajes

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>


#define PORT 9999
#define GROUP "225.0.0.37"

int main(int argc, char *argv[])
{
struct sockaddr_in addr;
int fd;
char *message="ieps!";

if((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)
{
perror("socket()");
exit(EXIT_FAILURE);
}

memset(&addr,0,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=inet_addr(GROUP);
addr.sin_port=htons(PORT);

while(1)
{
if(sendto(fd, message, strlen(message),
0, (struct sockaddr *) &addr,
sizeof(addr)) < 0)
{
perror("sendto()");
exit(EXIT_FAILURE);
}

sleep(1);
}

return 0;
}

listener.c - recepción de mensajes

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>


#define PORT 9999
#define GROUP "225.0.0.37"

int main(int argc, char *argv[])
{
struct sockaddr_in addr;
int fd, nbytes;
unsigned int addrlen;
struct ip_mreq mreq;
char msgbuf[256];
u_int yes=1;

if((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)
{
perror("socket");
exit(1);
}

if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
&yes, sizeof(yes)) < 0)
{
perror("setsockopt() SO_REUSEADDR");
exit(1);
}

memset(&addr, 0, sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=htonl(INADDR_ANY);
addr.sin_port=htons(PORT);

if(bind(fd,(struct sockaddr *) &addr,
sizeof(addr)) < 0)
{
perror("bind");
exit(1);
}

mreq.imr_multiaddr.s_addr=inet_addr(GROUP);
mreq.imr_interface.s_addr=htonl(INADDR_ANY);

if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
&mreq, sizeof(mreq)) < 0)
{
perror("setsockopt");
exit(1);
}


while(1)
{
addrlen=sizeof(addr);
if ((nbytes=recvfrom(fd, msgbuf,
sizeof(msgbuf), 0, (struct sockaddr *)
&addr, &addrlen)) < 0)
{
perror("recvfrom");
exit(1);
}

puts(msgbuf);
}

return 0;
}