@mfalkvidd , yes I also found this in MQTT GW example, thanks.
This seems to be not working on my ENC28J60 - as I can see the the default gateway setting is not taken into account. I will test with W5100.

Edit: I confirm that these settings work properly with W5100, just tested.

@LastSamurai please check the group ownership

$ ls -l /dev/ttyUSB0

Make sure the port you're using is included in EXTRA_JAVA_OPTS as described here

@hek
thanks for this really fast and motivating response, I will try!

With all my respect to the project and people behind it I believe that MQTT is more widely used than MySensors. So for me it would be more logical to add another MQTT client to the network rather than introduce any additional gateway. Just my 2¢.