Hello Sjur, Thanks for your reply. I am trying to understand CAIF protocol implementation in OFono. I am getting "Failed to create CAIF socket for AT" when i am trying to enable my modem. I appended below rule to 97-ofono-rules in /etc/udev. ATTRS{idVendor}=="major-number", ATTRS{idProduct}=="minor-number", ENV{OFONO_DRIVER}="ste" After appending the above line in rules file, my modem insertion and removal is getting recognized by oFono core daemon and displaying debug statements like below.. plugins/udev.c:remove_modem() xxxxxx. When i list my modem information with "list-modem" script. I got output as below.. [ /ste0 ] Interfaces = Powered = 0 Features = Online = 0 If i am connecting nokia Phone in PC Suite mode it is working fine. I am getting below information if i list nokia phone info using list-modem script [ /isigen1 ] Features = sim Powered = 1 Interfaces = org.ofono.Phonebook org.ofono.SimManager org.ofono.VoiceCallManager Online = 0 Model = Nokia E71 Manufacturer = Nokia Serial = xxxx Revision = xxx 09-02-10 RM-346 (c) Nokia [ org.ofono.Phonebook ] [ org.ofono.SimManager ] FixedDialing = 0 SubscriberNumbers = BarredDialing = 0 CardIdentifier = 123456566 LockedPins = PinRequired = none SubscriberIdentity = 123445566 Present = 1 [ org.ofono.VoiceCallManager ] EmergencyNumbers = 119 118 999 110 08 000 911 112 I found add_isi() (every modem vendor have their own in udev.c) function is getting get invoked, when i am dealing with nokia phone (PC Suite Mode). Is it necessary to have "add_ste()" function to work with CAIF protocol. Please suggest. Please suggest me how to start open contribution for oFono Testing. Thank You. Regards, Kris