int protonum = 0;
  struct protoent *p = getprotobyname ("IP");
  if (p)
    protonum = p->p_proto;

  //////////////////////////////////

  int sockin[portnum];
  for (int i = 0; i < portnum; ++i)
    {
      sockin[i] = socket (PF_INET, SOCK_DGRAM, protonum);
      if (sockin[i] < 0)
        {
          perror ("sockin");
          return 1;
        }

      struct sockaddr_in sockaddr;
      memset (&sockaddr, 0, sizeof (sockaddr));
      sockaddr.sin_family = AF_INET;
      sockaddr.sin_addr.s_addr = htonl (INADDR_ANY);
      sockaddr.sin_port = htons (21928 + i);

      int bindReturn;
      if ((bindReturn = bind (sockin[i], (struct sockaddr *)
                              &sockaddr , sizeof (sockaddr))) != 0)
        {
          perror ("bind");
          return 1;
        }
      else
        {
          fprintf(stderr, "sockin %d bound to port %d. Bind returned %d\n",
                  i, 21928 + i, bindReturn);
        }

      // Will Hall, 2007
      // INADDR_ANY will bind to default interface, specify alternate interface name
      // on command line on which to bind
      struct in_addr if_addr_in;
      if (interface_name)
        {
          if (!get_address (sockin[i], &if_addr_in, interface_name))
            {
              fprintf (stderr, "could not find interface address for %s\n",
                       interface_name);
              return 1;
            }
          if (setsockopt
              (sockin[i], IPPROTO_IP, IP_MULTICAST_IF, &if_addr_in,
               sizeof (if_addr_in)))
            {
              perror ("setsockopt:IP_MULTICAST_IF");
              return 1;
            }
        }
      else
        {
          if_addr_in.s_addr = htonl (INADDR_ANY);
        }

      struct ip_mreq mreq;
      mreq.imr_multiaddr.s_addr = inet_addr ("225.0.0.37");
      mreq.imr_interface.s_addr = if_addr_in.s_addr;
      if (setsockopt
          (sockin[i], IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,
           sizeof (mreq)) < 0)
        {
          perror ("setsockopt");
          fprintf (stderr,
                   "your linux kernel is probably missing multicast support.\n");
          return 1;
        }
    }