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Comment by j1elo | Hacker News Reader

Apple usually does excellent integrations between their devices. But I haven't used AirDrop so I'm not familiar with how it works: in order to create an ad-hoc wireless connection, if the devices were already connected to some wifi access point, are they temporarily disconnected for the duration of the ad-hoc connection?

If not, I'd guess that Apple devices maybe come with 2 WiFi adapters inside?

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Neither — frequency hopping is used so that the device can establish AWDL connectivity directly with nearby devices while maintaining a connection to an access point, while still only having a single Wi-Fi adapter.

> frequency hopping

That this is possible, and allows to maintain a dual connection to an AP and an ad-hoc connection to another device for AirDrop, sounds amazing. Now I want to learn more about that technique and where/how it can be applied to non-Apple devices!

Bluetooth does it too!

It's hard enough to get Bluetooth to connect to one device!

To be fair it’s great at connecting to every device within 100 meters other than the one in your hand.

The next version fixes this problem and uses less power.

And yes, I’m being sarcastic.

Honestly, I've been having excellent experience with BT (and headphones) with modern devices.

For example, my Lenovo T14s (2023 AMD version running the latest kernel) connects to my (5.2 version of BT) headphones really well. Similarly, my android phone connects to the same headphones and whatever device sends data, that's what I hear.

Similarly, my Steam Deck connects to two of the headphones I'm using (Sennheiser and Apple Airpods) seamlessly.

At first, I thought you were alluding to Bluetooth file sharing, which Apple doesn’t support.

I was referring to frequency hopping. In any case Apple does support Bluetooth file transfer on macOS, just not on iOS.

AirPlay and Miracast both rely on WiFi (in case of Miracast it's WiFi Direct, for AirPlay I'm not sure), so it's not uncommon for WiFi chips to maintain 2 connections at once.

No they don’t disconnect from WiFi and as of the latest iOS you can now leave airdrop radius and it will use the internet to continue transfer. Its magic

IIRC Apple uses some proprietary radio protocol (or maybe it’s just Bluetooth) to discover and communicate with nearby Apple products.

It uses Bonjour [1], which has an LGPL reimplementation named Avahi [2]

[1]: https://en.m.wikipedia.org/wiki/Bonjour_(software)

[2]: https://en.m.wikipedia.org/wiki/Avahi_(software)

For the sake of being picky, Bonjour is not a radio protocol (Layer 1), it’s a set of tools which enable zero config networking (Layer 2/3)

I agree, it's not a radio protocol and I wasn't trying to imply that it was. The person I was responding to posited it might be one and I pointed them to the protocol that's used without explicitly correcting them on that point.

Makes sense.

It can’t use just bonjour.

Apple devices can detect out of network devices as well.

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