Wake on Demand (http://support.apple.com/kb/HT3774) is great. It enables an unused device to go to sleep, while keeping the announced mDNS (multicast DNS) services alive. Just access one of the services and the device will be woken up automatically.

These scripts enables your non-Apple-devices, e.g. a server or NAS, to save energy by going to sleep while not in use. The Sleep Proxy Server will wake the device using Wake on LAN (WOL), as soon as a port matching an announced service is accessed. See http://en.wikipedia.org/wiki/Bonjour_Sleep_Proxy for more details.

To get this running, a Sleep Proxy Server on your local network is required. If present, it will announce itself via mDNS as _sleep-proxy._udp. Such a server is included in many Apple devices, like Apple TV or HomePod, as well as its (now outdated) network products "Time Capsule" and "AirPort Express". Any Mac running 10.6 or above can be turned into a sleep proxy server too.

SleepProxyClient is pretty stable and ready for everyday use. Please report issues to make it even more stable.

• python3
• dnspython (http://www.dnspython.org)
• and other useful python modules
• avahi-browse (to discover the Sleep Proxy Server and local services)
• systemd-sleep (pm-utils or similar power management tools can be used as well)

In addition, the host needs to support Wake on LAN.

SleepProxyClient works out of the box on Debian/Ubuntu. It's quite easy to install SleepProxyClient on other Linux distributions and UNIX/BSD systems too.

Download the package from releases and install it using dpkg -i sleepproxyclient_<version>_all.deb. Potential issues due to missing dependencies can be resolved by running apt --fix-broken install afterwards.

SleepProxyClient was tested on Linux but should work on other operating systems too.
The only Linux specific dependency (systemd-sleep) should be easily replaceable by other OS-specific power management tools like apmd on BSD. Just ensure the suspend-script (sleepproxyclient.sh) is called before suspending the system.

All locally announced services will be discovered via avahi-browse automatically - there is no need for manual configuration of services.

Create your own, or use the included checkSleep.sh script. The checkSleep.sh script needs to be called periodically to be able to suspend the host by it's own. This can be achieved by various means, e.g. by creating a cron job via crontab:

*/8 * * * * /bin/bash /usr/share/sleepproxyclient/scripts/checkSleep.sh

This job causes checkSleep.sh to be called every 8 minutes. Since two successfully calls are required to suspend the host, it will take at least 16 minutes until the host will enter suspend.

Some more parameters can be adjusted to fit your needs:

• List of network interfaces
  By default, all interfaces are used. Use the related option to adjust this behavior.

• List of preferred Sleep Proxy Servers
  By default, the Sleep Proxy Server with the best properties will be selected. The order of servers with the same properties is not defined. This option enables the specify preferred Sleep Proxy Serves that will be selected with precedence.

  A common use case for this is to prefer a wired Apple TV over a HomePod with weak WiFi coverage. Both advertise themselves with the same properties. Using this option, and specifying the Apple TV as preferred Sleep Proxy Server, adds additional reliability.

• Lease time (Time to live)
  The lease time (or TTL) controls the life time of the mDNS announcement. The host running SleepProxyClient will be woken up be the Sleep Proxy Server after this period to allow it to renew the announcement. The default value is 2 hours.

These settings can be configured via /etc/default/sleepproxyclient (or arguments of sleepproxyclient.py when called directly).

• sleepproxyclient.py
  The actual Sleep Proxy Client implementation.

• 00_sleepproxyclient
  This hook will be installed to /usr/lib/systemd/system-sleep/ and called by systemd-sleep before going to sleep. This script calls sleepproxyclient.sh which will then call sleepproxyclient.py.

• checkSleep.sh
  Is an example script, to show how to actually suspend the host. It does some checks - to determine if the host is currently in use or not - and will suspend the host after two successful calls. Suspend is initiated through systemctl suspend. This script is designed to be periodically called using a cron job. Any other custom / more advanced checks can be used as well. Just ensure to suspend the host using systemctl suspend to activate SleepProxyClient.