$p->ping(host[,timeout])
Pings remote host and waits for a response. Takes the following arguments:
Specified as either the hostname or the IP number of the remote host.
Optional, must be greater than 0 seconds if specified. Defaults to whatever was specified when the ping object was created.
If host cannot be
found or there is a problem with the IP number, returns undef.
Otherwise, returns 1 if the host is reachable and 0 if it is not.