SideMini

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Wake-on-LAN on a Mac, in practice

SideMini3 min read

Wake-on-LAN sounds like a solved problem and behaves like a coin toss. On a Mac it depends on the setting being on, the machine being asleep rather than off, and the network path carrying the packet at all. Here is what actually happens.

The setting

It lives in Energy settings as “Wake for network access”, and it is called womp in the underlying power management. On desktop Macs it is often on already; on laptops it is off on battery and cannot be relied on.

With it enabled, the Mac keeps a small part of its network hardware listening while the rest sleeps, ready for a specially formed packet addressed to its hardware address.

Why Ethernet works and Wi‑Fi usually does not

Over Ethernet the port stays powered and listening, and a magic packet from any device on the same network wakes the Mac reliably.

Over Wi‑Fi the radio cannot stay associated in deep sleep. Apple works around this with Bonjour Sleep Proxy: another always-on Apple device on the network, an Apple TV for instance, answers for the sleeping Mac and pokes it when something asks. If you have no such device, wireless wake will mostly fail and no amount of configuration changes that.

Sending the packet

  1. Find the Mac’s hardware address: System Settings → Network → your interface → Details.
  2. From another machine on the same network, send a magic packet with any wake-on-LAN tool, or on a Mac use wakeonlan from Homebrew.
  3. From an iPhone, several free apps do the same thing; they must be on the same network, not on cellular.
  4. From outside the house, wake a device that is already awake and send the packet from there. Waking across the internet means opening a port and rarely works.

Asleep is not the same as off

Wake-on-LAN wakes a sleeping Mac. It cannot start one that is shut down or one that lost power, because the network hardware is unpowered.

That is why “restart after a power failure” matters more than wake-on-LAN for a server: the outage is the case you cannot wake from. Turn both on and you are covered either way.

Or simply never sleep

For a Mac that serves something, the simplest configuration is the one with no wake step at all: never sleep, restart after a power failure, wake for network access as a belt-and-braces third setting. That is what SideMini’s Server mode switches on in one action, and it is the same trio you would set by hand.

SideMini is the small menu bar app that makes your iPad the screen of a Mac mini and connects it at every boot. Try it free for three days; $9 once, no subscription.

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