I've been reading the documentation on amanda.org, and it seems the
authors have this terminology flipped.  Servers always passively
*listen* for a connection, while clients are active initiators.  In
the Amanda model, the centralized backup host is actually a *client*,
because it's the active "consumer" that initiates connections, whereas
all the nodes on the network that have data to backup are servers
listening for a client - and serving the data on request.

I find it confusing to read the Amanda documentation, because it
appears the Amanda Core Team is calling the server a "client", and
vice versa.