Max speed bottleneck for multiple devices

[robm92]

My use-case for this framework is to send a large file to batches of devices from a single host.
Using the Apple Tetherator utility (Internet sharing over USB), I can send data at ~ 30MB/s to 16 devices using a Thunderbolt usb board (https://cambrionix.com/products/thundersync16-thunderbolt-usb-bridge/).

Using this framework, I can max the throughput of a single device but am only able to achieve 3.5 MB/s to 16 devices at a time.

Is this a limitation of usbmuxd or have I missed something?

My minor changes to your example project are as follows:

I can loop through a file in blocks of 8192 with a FileHandle and write the data to each device.

Where 'devices' is an array of connected Device objects and 'data' is a block of 8192 byte data.
for device in devices{ device.writeData(data: data) }

[jensmeder]

That's an interesting setup you have there. Unfortunately, I am unaware of the limitations of usbmuxd as it is a proprietary protocol developed by Apple but as the name suggests it is multiplexer. Therefore, the download speed of 3.5MB/s per device sounds reasonable given a USB2.0 interface when connecting 16 devices at once. I can only assume that the Thundersync16 has been optimized to work around these limitations somehow.

Just one thought: At the moment the DarkLightning sample applications run on the same port. You might be able to increase the speed if you could open a socket on a dedicated port for each device. That requires some modifications to both the iOS and macOS applications though.

[cbenhagen]

@robm92 did you find a solution to speed up your transfer?

[robm92]

I didn’t but haven’t revisited since.
I’m currently hosting the file on an apache server and downloading it to the devices over Tethered Caching to maximise the throughput of each device.

[cbenhagen]

Oh that sounds interesting as well. Do you happen to have more info on the Tethered Caching?

[cbenhagen]

@robm92 Sorry I have been a bit quick with my answer. I guess I can find all info myself. If you have tips you want to share I am happy to hear them of course.

[robm92]

In System Preferences -> Sharing you'll see a row named "Content Caching". Turn this on and select "Share: Internet Connection". This will turn on the Tethering service which allows connected devices to use internet over the cable, therefore letting you download files from a local server on the connected machine. You can monitor the status of the device connection in terminal with 'assetcachetetheratorutil status'