Filtering by client IP or hostname is not supported directly. However, an inetd daemon is shipped with the package which makes the use of tcpd possible. See tcpd(8) and related manpages for further details. Installation into /etc/inetd.conf is done with a line like this one:
3143 stream tcp nowait user /usr/sbin/tcpd
/usr/local/sbin/in.acng /var/run/apt-cacher-ng/socket
Use "make in.acng" to compile the wrapper client.