// create a socket of type PF_SYSTEM to listen for events

int s = socket(PF_SYSTEM, SOCK_RAW, SYSPROTO_EVENT);

// make sure we get receive the correct events

kev_request key;

key.vendor_code = KEV_VENDOR_APPLE;

key.kev_class = KEV_NETWORK_CLASS;

key.kev_subclass = KEV_ANY_SUBCLASS;

//

int code = ioctl(s, SIOCSKEVFILT, &key);

kern_event_msg msg;

// endless loop

while(1) {

// get notification

code = recv(s, &msg, sizeof(msg), 0);

// check type of event

switch(msg.event_code) {

case KEV_DL_IF_DETACHED:

// interface is detached

break;

case KEV_DL_IF_ATTACHED:

// interface is attached

break;

case KEV_DL_LINK_OFF:

// interface is turned off

printf("link off\n");

break;

case KEV_DL_LINK_ON:

// interface is turned on

printf("link on\n");

break;

}

}

return 0;

}