[Libguestfs] Exporting ttyACM0 via nbd

Hi all, I'm trying to export the serial and i2c interfaces of a RaspberryPi to another Linux host. The server OS is Raspbian stretch with nbdkit 1.1.12. If required, I can compile try to compile / backport a newer version on my own. I tried with /usr/bin/nbdkit --newstyle -g dialout -v file file=/dev/ttyACM0 but it says nbdkit: error: file is not regular or block device: /dev/ttyACM0 Also streaming does not seem to fit to my use case since I will need bi-directional communication. Is what I'm trying to do possible? Can you give me some hint / reference to look into? Thanks in advance, All the best Marco