I'd like to check the status of a Receiver with Nagios. The SBR has a fixed IP address. Sometimes it gets into a state where it responds to pings but doesn't respond to the Controller or SqueezeCenter. It looks like it periodically sends a packet from port 46539 to port 3483 on the SC server, which acknowledges. Nmap shows all the ports on the SBR as closed. Is there any automatable way, besides pinging, to actively check whether an SBR is up?