while (1) {
         cnt = recvfrom(sock, message, sizeof(message), 0,
                (struct sockaddr *) &addr, &addrlen);
         //printf("%d n",cnt);
         if (cnt < 0) {
            perror("recvfrom");
            exit(1);
         } else if (cnt == 0) {
            break;
         }
         printf("%s: message = "%s"n", inet_ntoa(addr.sin_addr), message);
         addr.sin_addr.s_addr = inet_addr(EXAMPLE_GROUP);
         cnt = sendto(sock, message, sizeof(message), 0,
          (struct sockaddr *) &addr, addrlen);
         if (cnt < 0) {
            perror("sendto");
            exit(1);
         }

    }