Motivation
After the Bluetooth Activation the access to the PDA is available via Bluetooth and therefore the PDA does not have to be in the Cradle to develop with it.
What is RFCOMM?
The Bluetooth protocol RFCOMM is a set of commands that is used to emulate one or multiple serial interfaces. It is therefore sometimes referred to Serial Port Emulation. Bluetooth profiles like SPP are set up on top of this protocol.
Setup the RFCOMM Connection (virtual ttyS)
Command on the Linux system
rfcomm listen /dev/rfcomm1 5
(start a new rfcomm "server" on channel 5)
Command on the PDA
rfcomm connect /dev/bluetooth/rfcomm/0 00:A0:96:1F:21:81 5
(connect virtual interface 0 with address 00:A0:96:1F:21:81 on channel 5)
Setup a PPP Connection over the virtual interfaces
Command on the Linux system
pppd /dev/rfcomm1 115200 192.168.201.1:192.168.201.2 noauth nodetach
Command on the PDA
pppd /dev/bluetooth/rfcomm/0 115200 192.168.201.2:192.168.201.1 noauth nodetach
Now you have a working TCP/IP connection between the PC (192.168.201.1) and the PDA (192.168.201.2).