udp로 broadcast하는 방법

다시 해보니까 리눅스에서는 보내는 것이 안되고 있습니다.
받는 것만 됩니다.
리눅스에서 sendto시에 Network is unreachable 에러가 납니다.

int tosd;
struct sockaddr_in toaddr;
char buffer[1024];
port = DEFAULT_PORT;
strcpy(buffer,"hello");
tosd = socket(AF_INET, SOCK_DGRAM, 0);
if ( tosd < 0 ) perror("socket failed");
bzero(&toaddr, sizeof(toaddr));
toaddr.sin_family = PF_INET;
toaddr.sin_port = htons(port);
toaddr.sin_addr.s_addr = INADDR_BROADCAST;
if ( setsockopt(tosd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) != 0 )
    perror("set2 SO_BROADCAST failed");
if ( setsockopt(tosd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) != 0 )
    perror("set SO_REUSEADDR failed");
while(1) {
    if (sendto(tosd, buffer, strlen(buffer), 0, (struct sockaddr*)&toaddr,
                sizeof(toaddr)) < 0)
        perror("sendto");
    sleep(1);
}

$ /sbin/ifconfig
eth0      Link encap:Ethernet  HWaddr 00:02:2A:C7:39:39
          inet addr:10.11.11.12  Bcast:10.11.255.255  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:143005 errors:6 dropped:0 overruns:0 frame:0
          TX packets:89225 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:74799630 (71.3 Mb)  TX bytes:31730357 (30.2 Mb)
          Interrupt:10 Base address:0xe000