On Windows 2000 we only get a WSAECONNRESET from recv and not from send.
The implication is that we can only throw PortUnreachableException in
DatagramSocket.receive and not in DatagramSocket.send. This is
inconsistent with the behaviour on Solaris & Linux.

In addition Windows appears to track the number of ICMP port unreachable
messages received so that we get a WSAECONNRESET per icmp packet. This
is inconsistent with normal Solaris/Linux behaviour whereby the socket is
reset after ECONNREFUSED is received.

We need to examine these issues so that we have simulate the right
behaviour on Windows 2000.

alan.bateman@ireland 2001-03-28