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Re: USB "null modem" cables and related Linux driver questions

On 05/31/2018 10:07 PM, Stefan Monnier wrote:
I have two computers with USB ports.
I wish them to communicate as simply as mid-20th-century computers did.

What kind of "communicate" do you need there?

Essentially any ;/
In fact one of the thought experiments I was pursuing was how to do file copying/sharing over RS232 - even I would not actually attempt to implement.

The "way back machine" to simulate a "null modem" serial cable exists,
as you've seen, but it's rarely the best solution for nowadays's needs,

"Best" is not an invariant absolute.

since nowadays connecting two computers is something completely normal,
supported by a deluge of tools, but they all expect a "network"
connection rather than a serial cable.

In most cases those two computers also have ethernet or wifi "ports" so
you can connect them via such a network (which usually offers faster
transmission than a serial cable, lets you seamlessly multiplex several
connections, and lets you use the many tools working over the network to
connect computers).

An explicit requirement is a wired, NOT WiFi, connection.
I that seriously. My internet access is a WiFi hotspot with its WiFi capability disabled.

In some cases one of the two computers's USB port is an "OTG" port,
meaning that it can act either as "master" or not, in which case you can
just use a regular USB cable (and usually you then configure the OTG
side to pretend it's a network card, so it ends up looking to the
software like you've connected the two machines via an ethernet cable.
That's what I use between my BananaPi "router" and my office desktop).

I saw it and it meets most (all?) my requirements except my reading suggested:
  1. obsolete
  2. available only for Windows/Mac
  3. no way to determine if any of machines were equipped

If none of that are options, you can resort to using an "ethernet
dongle" on both sides and an ethernet cable between the two.

That's a 1 versus 3 items required per connection.

All of those things will typically work "out of the box" on a vanilla
Linux kernel (the usbnet drivers have been incorporated years ago).

Oh, and in case those computers are somewhat old, they may also come
with Firewire ports, and those (contrary to USB) don't have the
"slave/master" distinction so you can connect your computers this way
with a plain normal Firewire cable (and make it appear to the software,
again, as some kind of ethernet-like connection).


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