#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>

int main(int argc,char *argv[]) {
 int s=socket(AF_INET,SOCK_RAW,atoi(argv[2]));
 char packet[1501];//mtu of an interface. including headers though. meh.
 int n;
 struct ip_mreq mreq;
 struct sockaddr_in sa;
 int one = sizeof(struct sockaddr_in);
 setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
 mreq.imr_multiaddr.s_addr=inet_addr(argv[1]);
 mreq.imr_interface.s_addr=htonl(INADDR_ANY);
 setsockopt(s,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq));
 while((n=recvfrom(s,packet,sizeof(packet),0,(struct sockaddr *)&sa,&one)) > 0) {
  printf("%s ",inet_ntoa(sa.sin_addr));
  fflush(stdout);
  write(1,packet,n);
 }
}