c#, the application will close after running, why?

Question

i have wrote this code to check connectivity to a host. but it always returns false. why?

for (int i = 0; i < 4; i++) {
    if(InetAddress.getByName(address).isReachable(1000)) {
        // return true
    } else {
        // return false
    }
    Thread.sleep(1000);
}