This RFE is submitted to track the requirement to test the reachability
of a host (or more likely an InetAddress). This RFE stems from the
feedback to 4093850 "ICMP protocol support a.k.a. PING applets" where
it clear that many developers have a basic requirement to test if a
host was reachable (something akin to the ping utility).

In its simplest form it we could test if a host is reachable
within a specified timeout. Another variant could be to test if
a host is reachable from a specified java.net.NetworkInterface.

Implementation-wise there needs to be flexibility to choose how
reachability is determined. If we can create an ICMP socket then
we can send/receive an echo request/reply ala classic ping.
Alternatively if we can't create an ICMP socket then a UDP or TCP
approach might be used (for example we could send a UDP packet to
the echo port and handle timeout/port unreachable).