Setting up communications with the Bluetooth device

This is the second phase in using a GPRS cellphone as a modem via Bluetooth.

After you've configured the pairing between cellphone and Ubuntu, the next thing you need to do is set up the RF communications between the cellphone and the computer.

Step 1. What's the channel?
The cellphone's dial-up networking service listens at a particular channel. In my setup it's channel 1, but you'll want to be sure. To check what the channel is, run sdptool browse. A sample output is:

Inquiring ...
Browsing 00:17:B0:B4:52:C8 ...
Service Name: Dial-up networking
Service RecHandle: 0x10010
Service Class ID List:
"Dialup Networking" (0x1103)
"Generic Networking" (0x1201)
Protocol Descriptor List:
"L2CAP" (0x0100)
"RFCOMM" (0x0003)
Channel: 1
Language Base Attr List:
code_ISO639: 0x656e
encoding: 0x6a
base_offset: 0x100
Profile Descriptor List:
"Dialup Networking" (0x1103)
Version: 0x0100

Note that in the Protocol Descriptor List, it specifies the channel 1.

Step 2. What's the device ID?
As in the previous stage, you can run hcitool scan to figure this out. My output is:

Scanning ...
00:17:B0:B4:52:C8 Nokia6233

Step 3. Configuring rfcomm.conf
Armed with the information above, you can now edit /etc/bluetooth/rfcomm.conf. Configure it with the following settings:

rfcomm0 {
bind yes;
device 00:17:B0:AF:E4:A9;
channel 1;
comment "nokia";
}

And you're done! The next step will be to set up PPP to use this connection.

See also the excellent Bluetooth tutorial from Gentoo, which explains Bluetooth configuration files in greater detail.