Comment 29 for bug 570692

I'm seeing this error in 10.10 (my user is in the dialout group, /dev/rfcommX is being set up correctly as root:dialout). It turns out that the problem is intermittent however.

I connect my device by using Bluetooth Manager (right click, select Connect To: Serial Service). The port gets set up, but I can't access it. I'm testing with:
  echo 1 > /dev/rfcomm0
When it fails, I get:
  bash: /dev/rfcomm0: Device or resource busy

If I toggle the connection (right click, disconnect, then reconnect) a couple of times, I'm able to access the port.

This is happening under VMware Fusion using the Mac's built-in Bluetooth module and the btusb-dkms workaround described at https://help.ubuntu.com/community/MacBookPro6-2/Maverick#Package%20Support%20for%20Intel%20Macs.