[nmglug] APC UPS question

[Ed Brown]

Can anyone explain about the communication that takes place between a 
server and a UPS device that protects it and is capable of signaling 
it to shutdown?  Mainly what I want to know: is ALL communication 
between the UPS and server initiated by the UPS?  (Other than 
configuration of the UPS that might happen to be done from the 
server.)  Unit in question is an APC AP9617.  If you know what 
ports/protocols are involved, even better.

thanks in advance,
Ed