I use a scribbler robot with an IPRE fluke for my classes. On Ubuntu, I have a funky situation where the fluke does not work correctly the very first time I connect to it. Dan Walker, of BetterBots has captured all of the bluetooth data and says that Ubuntu is sending “AT+GCAP” data (AT command for a modem to “Request Complete Capabilities List”) to the fluke when first connected. This command gets the fluke into an unstable state and make it not work until rebooted (a possible problem with the fluke…but really, should custom hardware have to anticipate receiving random AT commands?)

The extra data doesn’t happen on subsequent connections to the same /dev/rfcomm* port until the laptop is rebooted. We suspect that the network manager may be the culprit. (I stay logged in until rebooting, so perhaps if a user logged out that would also trigger the network manager to re-probe?)

Thanks to Doug Harms for the solution…this is the ModemManager service probing all bluetooth serial ports. To disable it you can issue the following command (all on one line…):

sudo mv /usr/share/dbus-1/system-services/org.freedesktop.ModemManager.service
/usr/share/dbus-1/system-services/org.freedesktop.ModemManager.service.disabled