Apt-cacher version 1.7.13+deb9u1: Daemon mode
Usage:

Edit /etc/apt/apt.conf to include the configuration

Acquire::http::proxy=http://mirror.puppet.hosts.net.nz:9999
Alternatively, edit /etc/apt/sources.list so all your HTTP sources are prepended with the address of your apt-cacher machine and the port, like this:
deb http://example.debian.org/debian unstable main contrib non-free
becomes
deb http://mirror.puppet.hosts.net.nz:9999/example.debian.org/debian unstable main contrib non-free

Configuration: /etc/apt-cacher/apt-cacher.conf

Directive Value
admin_email root@localhost
allowed_hosts *
allowed_hosts_6 fec0::/16
allowed_ssl_locations
allowed_ssl_ports 443
cache_dir /var/cache/apt-cacher
clean_cache 1
concurrent_import_limit 2
curl_idle_timeout 120
curl_throttle 10
daemon_port 9999
data_timeout 120
debug 0
denied_hosts 0
denied_hosts_6 0
distinct_namespaces 1
expire_hours 0
generate_reports 1
group www-data
http_proxy proxy.example.com:8080
http_proxy_auth *********:*********
libcurl_socket /var/run/apt-cacher/libcurl.socket
limit 0
limit_global 0
log_dir /var/log/apt-cacher
path_map debian ftp.us.debian.org/debian ; security security.debian.org/debian-security ; debian-archive archive.debian.org/debian; ubuntu archive.ubuntu.com/ubuntu ; ubuntu-security security.ubuntu.com/ubuntu ; ubuntu-old old-releases.ubuntu.com/ubuntu/ : backports www.backports.org/debian ; gfarm datafarm.apgrid.org/software/debian-sarge/ ; debian-volatile http://volatile.debian.net/debian-volatile ; backports www.backports.org/debian ; grsecurity molly.corsac.net/~corsac/debian/kernel-grsec/packages ; mariadb mirror.aarnet.edu.au/pub/MariaDB/repo/5.5/debian mirror.jmu.edu/pub/mariadb/repo/5.5/debian
request_empty_lines 5
request_timeout 10
return_buffer_size 1048576
reverse_path_map 1
supported_archs avr32, amd64, alpha, arm, arm64, armel, armhf, hppa, hurd-i386, i386, ia64, kfreebsd-amd64, kfreebsd-i386, m32r, m68k, mips, mipsel, netbsd-alpha, netbsd-i386, powerpc, powerpcspe, ppc64, s390, s390x, sh4, sparc, sparc64, x32
ubuntu_release_names dapper, edgy, feisty, gutsy, hardy, intrepid, jaunty, karmic, lucid, maverick, natty, oneiric, precise, quantal, raring, saucy, trusty, utopic, vivid, wily, xenial, yakkety
use_proxy 0
use_proxy_auth 0
user www-data
checksum_files_regexp (?:^|/)(?:(?:Sources|Packages)(?:\.(?:x|g)z|\.bz2)?|(?:In)?Release|Index(?:\.bz2)?)$
index_files_regexp (?:^|/)(?:Index(?:\.bz2)?|(?:Sources|Packages|release)(?:\.(?:x|g)z|\.bz2)?|Release(?:\.gpg)?|InRelease|Contents-(?:[a-z]+-)?[a-zA-Z0-9]+\.gz|(?:srclist|pkglist)\.[a-z-]+\.bz2|Components-(?:avr32|amd64|alpha|arm|arm64|armel|armhf|hppa|hurd-i386|i386|ia64|kfreebsd-amd64|kfreebsd-i386|m32r|m68k|mips|mipsel|netbsd-alpha|netbsd-i386|powerpc|powerpcspe|ppc64|s390|s390x|sh4|sparc|sparc64|x32|all)\.yml\.(?:x|g)z|icons-(64|128)x\g{-1}\.tar\.(?:x|g)z|Translation-[a-z]{2,3}(?:_[A-Z]{2}(?:\.[a-zA-Z0-9-]+)?)?(?:\.gz|\.bz2|\.xz|\.lzma)?)$
installer_files_regexp (?:^|/)(?:vmlinuz|linux|initrd\.gz|(?:[a-z0-9][-+.a-z0-9]*_(?:\d+:)?[0-9][-+:.~a-zA-Z0-9]*[_\.])?changelog|NEWS\.Debian|(?:dapper|edgy|feisty|gutsy|hardy|intrepid|jaunty|karmic|lucid|maverick|natty|oneiric|precise|quantal|raring|saucy|trusty|utopic|vivid|wily|xenial|yakkety)\.tar\.gz(?:\.gpg)?|(?:by-hash/(?i:MD5SUM/[0-9a-f]{32}|SHA1/[0-9a-f]{40}|SHA256/[0-9a-f]{64}))|(?:Devel|EOL)?ReleaseAnnouncement(?:\.html)?|meta-release(?:-lts)?(?:-(?:development|proposed))?)$
package_files_regexp (?:(?:^|/)[a-z0-9][-+.a-z0-9]*_(?:\d+:)?[0-9][-+:.~a-zA-Z0-9]*(?:_(?:avr32|amd64|alpha|arm|arm64|armel|armhf|hppa|hurd-i386|i386|ia64|kfreebsd-amd64|kfreebsd-i386|m32r|m68k|mips|mipsel|netbsd-alpha|netbsd-i386|powerpc|powerpcspe|ppc64|s390|s390x|sh4|sparc|sparc64|x32|all)\.(?:u|d)?deb|\.dsc|\.tar(?:\.gz|\.bz2|\.xz)|\.diff\.gz)|\.rpm|index\.db-.+\.gz|\.jigdo|\.template)$
pdiff_files_regexp (?:^|/)2\d{3}-\d{2}-\d{2}-\d{4}\.\d{2}\.gz$
skip_checksum_files_regexp (?:^|/)(?:(?:In)?Release|Release\.gpg)$
soap_url_regexp ^(?:http://)?bugs\.debian\.org(?::80)?/cgi-bin/soap\.cgi$

License

Apt-cacher is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

Apt-cacher is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

A copy of the GNU General Public License is available as /usr/share/common-licenses/GPL in the Debian GNU/Linux distribution or on the World Wide Web at http://www.gnu.org/copyleft/gpl.html. You can also obtain it by writing to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.