Martin Gregorie  writes:
> Has anybody tried using a asynchronous, i.e. poll() based i/o, to
> handle bidirectional data transfers over a USB-serial adapter?

Not personally but one of our products presents as a USB serial adapter
so I have good reason to believe that it works in general.

> I have a setup that works as expected when talking to a program that
> emulates the target via a socket session, but appears to send but not
> receive messages when connected to the target device via a USB-serial
> adapter.

1) strace your program to get some visibility of what’s going on.
2) See if it works with blocking IO (no poll).

--
https://www.greenend.org.uk/rjk/

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