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Comment by zbrozek | Hacker News Reader

In a USB type-C universe, why can't I even share files between two computers? If something so basic-and already possible with existing standards-isn't working today, why should I think that an announcement like this is anything more than hot air?

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USB is directional protocol so there is always host and devices. USB-C lets devices negotiate the direction for power and data separately. This means that if they were doing USB media, one device has the files and the other can access them.

There used to be cables with USB connectors on both ends and dongle in middle, that did Ethernet between devices. That would be possible to do with USB-C, effectively two USB-C Ethernet adapters connected together. I had never thought to use two USB-C Ethernet adapters with short Ethernet cable, I bet you hadn't thought of it either.

The problem is that this isn't needed very much. Computers are almost always connected to local network, or can make Wifi Direct network if needed. There are programs for making local file sharing but they aren't common enough to rely on them.

It would be nice to have Ethernet over USB without needing adapter and using the high speeds of USB3 and USB4.

I did think about that and ultimately did do that. It's just not what the hardware could do, and it's a crappy solution. I don't often wander around with spare USB NICs, but a double ended type-C is in my standard kit.

There's no hardware reason why two type-C ports couldn't adopt host and device roles and become a NIC. Could be an RNDIS class endpoint or emulate one of the ultra common ASIX ICs. That's basically what my phone does when USB tethering.

Why does my desktop computer do less?

It's a little janky (you have to boot to recovery mode), but you _kinda_ can with modern macs by using Target Disk Mode.

The drive appears as a network share, but it's not bidirectional, in that you can read/write from/to the target device, but the target device do the same to you.

That's undershooting the possibility by a lot. If I plug two computers into each other via USB I would expect the OS on each to establish a network link at the best-available bandwidth.

That’s what already happens (at least with TB, USB 4?).

10 Gbps networking. Although it seems to have really high latency for whatever reason.

I'd like it to work USB 1.1 through 3.2, not just Thunderbolt. We have dual role, why aren't we using it? Host side thinks it's talking to a NIC, device side acts like a NIC.

On Mac, You can establish a thunderbolt-bridge network connection and then share files.

But it's not automatic. You gotta do it manually https://support.apple.com/guide/mac-help/ip-thunderbolt-conn....

I would have expected airdrop to automatically switch to thunderbolt if such a connection exists, but it doesn't.

Unless something has changed in recent macOS versions, by default:

1. Thunderbolt Bridge exists and is enabled.

2. All active (enabled, connected) interfaces get link-local IPv6 addresses.

3. All active interfaces without static or DHCP-assigned IPv4 addresses get link-local IPv4 addresses.

3. Multicast DNS (Bonjour) is enabled.

So basic networking should be automatic, though no file sharing services are enabled by default.

That's great! I wonder when they will automatically switch Airdrop over to thunderbolt when one is available.

I'd like to do this with actual universal serial bus (USB), not peripheral component interconnect express (PCIe) on a universal serial bus connector.

It was weird and cool when using firewire, I connected two powerbooks together, using one as a simple external disk.

TBF though, you could always just set up a mesh network. Wait. Does mesh network functionality still exist?

You can, just use Linux. I transfer files between my laptop and cell phone and other devices all the time.

I recently spent longer than I care to admit researching how to use USB to connect two Linux computers, but without bearing fruit. How do you do it?

What do you do? Samba plus Bluetooth?

Cool. How?

Enable USB debugging on your phone, and then use adb.

That's Android, and not serving the stated purpose of moving files between Linux computers.

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