ause on a laptop, DNS is one of the first services lost when the network
 goes; you are implicitly offline.
 <p/>
 If a URL is supplied instead of a host, the hostname is extracted and used in
 the test--all other parts of the URL are discarded.
 <p/>
 The test may not work through firewalls; that is, something may be reachable
 using a protocol such as HTTP, while the lower level ICMP packets get dropped
 on the floor. Similarly, a host may be detected as reachable with ICMP, but not
 reachable on other po