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fiddyschmitt

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Hi Andrew, there's just one writer (which can tunnel multiple TCP connections).

Arbitration was indeed one of the trickiest bits. Originally I pre-reallocated the full file size (10 MB). Then used an integer at the beginning of the file to signal to the other side that a block was ready. The other side repeatedly read that int, and read the corresponding part of the file. But writing twice (once for the data, once for the int) had a significant performance impact.

In the end, what worked best was not pre-allocating the file. Rather letting the file grow whenever the writer writes to it. The reader knows when data is available by doing a PeekChar() in a tight loop. It's surprisingly fast, and accurately reflects the state of the file.

Hi Bawolff! Yes that's a great combo. I guess File Tunnel provides a couple of things that makes the tunnel maintenance a bit easier.

1. It gracefully supports each side of the tunnel turning on and off.

2. It accepts any number of clients, and forwards them through the tunnel.

3. It recycles the shared file.

Thanks J :) Absolutely! I did try various flags to optimise performance. For CreateFile (which in .NET is wrapped by the FileStream class) I tried FILE_WRITE_THROUGH (which is FileOptions.WriteThrough in .NET), and found it impacted performance quite a lot.

The key to high performance as you rightly pointed out was preventing flushing. In the end, what worked best was reducing the number of writes to disk (which is the bottleneck). I did that by buffering 10-50 ms worth of TCP data, coupled with only flushing explicitly (using a large buffer so that neither BinaryWriter or FileStream flush automatically).

If you only have two PCs, you only need to run the program on one of them.

When it detects a USB device being plugged in, it changes the monitor input to this computer. When a USB device is removed, it changes the monitor input to the other computer.

Yes only one computer needs to have Windows and run the program.

If it detects the USB device being inserted, it changes monitor inputs to the Windows computer. If it detects the USB device being removed, it changes monitor inputs to the Linux computer.

That is so cool!!

Yes I noticed prices had increased a bit over the last couple of years. Perhaps there's a market for yours.

Interesting to hear that some USB switchers don't quite work in Linux. I had assumed they were just very basic USB hubs so no special drivers required. I know some USB switches have fancier things like inter-PC file transfer or mouse sharing like this one (https://www.aliexpress.com/item/1005006202631772.html), and that often requires special software and drivers.