This is a sort of errata post for Connecting more than one computer to the USV (I), the first part of this series: I’ve found a better suited network port (the NETPORT directive) for the communication between master and slaves. It’s the port number 3493, declared as “Network UPS Tools” port in FreeBSD. Choosing the network port for an application can be picky in some situations. One has to weight the inconvenience for choosing a non-default port (this would be a just to big burden for http servers) against the security implications (e.g. secure shell server not running on port 22 is a good idea) and the possibility that the port may be used by other (or future) applications. In this case it’s a sure bet, since the port is reserved (by IANA?) for this kind of use. And it’s not very likely that one machine is connected to two different USVs (for such power-users I would suggest getting one of those network enabled USVs). All in all it doesn’t make any difference in the network communication, so you can ignore this entire posting, but one of the administration maxims I love, is to keep things simple and using a network port dedicated to such purposes fulfills this principle.