Example program on how to use standard C network library to subscribe to a multicast server.

multicast_std.cpp

#include <iostream>
#include <netdb.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>
#include <sys/socket.h>

#define BUFFERSIZE 2048

int main(){
  int sockDesc = 0;
  if ((sockDesc = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
    std::cout << "Socket creation failed\n";
    return 0;
  }
  
  int32_t port = 12911;
  std::string ip = "237.0.0.11";
  
  struct ip_mreq multicastRequest;
  multicastRequest.imr_multiaddr.s_addr = inet_addr(ip.c_str());
  multicastRequest.imr_interface.s_addr = htonl(INADDR_ANY);
  if (setsockopt(sockDesc, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *) &multicastRequest, 
    sizeof(multicastRequest)) < 0) {
    std::cout << "Failed to join multicast group\n";
    return;
  }
  
  // If you want the socket to be non-blocking, set the timeout.
  // It is set to 5 seconds here.
  struct timeval tv;
  tv.tv_sec = 5;
  tv.tv_usec = 0;
  setsockopt(sockDesc, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,sizeof(struct timeval));

  char buffer[BUFFERSIZE];
  while(true){
    if ((bytesRead = recvfrom(sockDesc, (void *) buffer, BUFFERSIZE, 0, NULL, NULL)) < 0) {
      if(errno != 11){
        std::cout << "Socket read " << bytesRead << " errno " << errno << ". Closing.\n";
        return;
      }
      continue;
    }
  }
}