Try to establish a connection to a service running on the other system or use the
Ping Class (System.Net.NetworkInformation)[
^].
Note that both methods may not work when filtered out by firewalls.
With Windows you can also use the
Net view[
^] command. Without any options it will display a list of computers in your current domain. But execution requires usually some time and you have to resolve the system names to get the IPs.