IB 5.6 guardian restarts after server reports INET/INET_connect: getservbyname failed, error code = 11004

Why would the server be calling getservbyname (these lines are preceeded
with (Server) tag)?

The gds_db entry in the services file is fine, users can connect.  This
error message preceeds a restart of ibserver.exe by interbase guardian.
    We're seeing an aweful lot of these in our customers logs.

The next error always seems to be: Unable to complete network request to
host "server". Failed to locate host machine. Undefined service gds_db/tcp

So, the server is trying to find a host?  That doesn't make any sense??