Why hotel Wi-Fi hides your tablet from your Mac, and how to get around it

Guest Wi-Fi keeps guests apart, including your own devices

Many hotel, café and conference networks switch on a feature called client isolation. Cisco's Meraki documentation describes it as a security feature that prevents wireless clients from communicating with one another, and recommends it for guest networks. Every device gets the internet, and no device can reach the one in the next room.

It can't tell your tablet from a stranger's laptop, so your own two devices are kept apart too. Google's own help pages warn that on a hotel or public network with client isolation you can't set up its streaming devices either.

Finding a device needs a friendly network

Apps that "just find" a printer, a speaker or your Mac ask everyone on the network "who's there?" using multicast DNS, a protocol designed to stay on that local network. Apple's own security note on Bonjour, its version of it, says the design "assumes cooperation of participants", which is exactly what a public network can't promise.

So the hotel isn't being difficult; it's being sensible. You just need a network where you are the only guest.

Bring your own network: your tablet's hotspot

Your tablet can make a small Wi-Fi network of its own. Join your Mac to it and the two are alone on it, so they find each other at once. Wing Display's second screen works there exactly as at home, and it's free.

1. Turn on the hotspot

   In the tablet app, pick Tablet hotspot, follow its Hotspot settings link and switch the hotspot on. Not every tablet has one; look for Mobile Hotspot in Settings.

2. Join it from your Mac

   Choose the tablet's network in your Mac's Wi-Fi menu, like any other, and make sure Wing Display is started on the Mac.

3. Tap Connect

   Your Mac appears in the tablet app. Tap Connect, and click Allow on your Mac the first time.

What the hotspot changes

• The picture never touches the internet. It goes straight from your Mac to your tablet, encrypted, so the second screen itself uses no mobile data.
• Your Mac's other traffic does. While it's on the hotspot, updates and downloads run over the tablet's data plan, and Google notes that some carriers limit or charge extra for tethering.
• Plug the tablet in on a long session: a hotspot uses more battery.

No hotspot, or want your Mac to stay on the hotel's Wi-Fi? Pro adds a USB cable connection that needs no network at all.

What it costs

The Mac app and the second screen over Wi-Fi or your tablet's hotspot are free to use. Pro adds the USB connection, touch and the pen: $2.99 a month or $24.99 a year in US dollars, through Google Play, with 14 days free for first-time subscribers. Compare the plans.

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