When the client app starts, it can try to open TCP connections to port 3015(Datasocket) and port 3363 (default TCP VI Server) to see if they are listened to by the server. If the connections fail the server is not running. If they succeed, close them.
You could also set the server to reply to some UDP broadcast request when it is running. That allows to identify which servers are online on the network without knowing their IP.
