 Do you treat your computer and cellular telephone as indispensable necessities, somewhere between running water and your favorite pair of pliers? Wait until you put the two together; a computer connected to a cellular telephone is way more fun than either alone.
There are lots of ways cellular phones and desktop computing meet—far more than we can list in this month’s column. Let’s look at one of them with enough care to be sure your own experiments will be successful.
First, we need a few ground rules. Our look at cellular-computer cooperation focuses on command line operations rather than GUI applications. If your usual Linux experience is limited to its GUIs, you’ll want a few of the tips that follow. For telephony, Linux is on the undercooked side; you’ll achieve the most rewarding results when you can work from the command line.
 Dial-up Done Wirelessly
The first way computers and cellular handsets came together in the ’90s remains important today. A computer can establish a dial-up connection through a cellular handset. But if you’re going to go this route, sign up for a cellular data plan, which will be much cheaper, faster, and more reliable than over-the-air dial-up. However, it’s still good to know about dial-up capabilities for occasional use. For a modest cost, you can use your computer and cell phone to access, at limited speed, anything on the ’Net for a few minutes. | 
It may seem like a lot of steps, but using a
Bluetooth-enabled
cell phone with
your computer
to access the
Internet follows
a logical progression. |
Although it’s possible to connect your cell phone and computer together in a variety of ways, using the Bluetooth wireless protocol is actually probably easier than attempting a cable connection. To successfully connect to your ISP (and, consequently, the Internet) from your cell phone over Bluetooth, you need the following: a recent 2.6.x kernel with Bluetooth, ppp, and networking enabled; pppd; and BlueZ to handle Bluetooth connectivity. The specific configuration we used included a 2.6.15 kernel for Linux, release 2.4.4b1 of pppd, and 2.24 of BlueZ.
Along with the installations listed above, you’ll also need to configure your handset for connection to your ISP. Don’t get hung up on the term “dial-up,” either. It’s generally not feasible to make an Internet connection through a cellular telephone using the same software as you would for a conventional landline; the process before and after dialing is different. Instead, cellular telephones embed special data-connect software that your computer must interface. Consult your ISP for this vendor-dependent step.
Install Bluetooth
To set up Bluetooth on a Linux box requires a Bluetooth-enabled kernel. All recent major distributions include Bluetooth support in the kernel; you’ll only have to make a change if you compiled a kernel on your own and deliberately choose not to enable Bluetooth.
With the right kernel in place, you’re ready to install the BlueZ application. BlueZ offers a comprehensive range of Bluetooth-related utilities for Linux. Other distros might have a different installation shortcut, but for Debian-derived distributions such as Ubuntu, you need to log in with root access and type apt-get install bluez-utils, pressing ENTER when you finish.
Next, enable your Bluetooth hardware. Whether your computer has integrated Bluetooth capabilities or you have a USB adapter, you need to set a PIN for your computer. To set a PIN of 1234, type echo 1234 >/etc/Bluetooth/pin and press ENTER. Your mobile handset will prompt you during its Bluetooth configuration for that same PIN.
Set up the connection
Next, enable Bluetooth on your mobile phone and set it to Discoverable, which lets other Bluetooth devices detect your mobile phone. (Remember to turn Bluetooth off after you finish using it because it’s too easy for an intruder to harm an unattended device with live, unguarded Bluetooth capabilities.)
Next, scan your Bluetooth neighborhood. Although such GUI utilities as KDE’s Konqueror make scanning possible, we’ll focus on the command line. After we typed hcitool scan and pressed ENTER, we received the following output:
Scanning . . .
00:02:72:04:16:9E HESUS
00:09:2D:2C:A2:1B mHesus_new
In this case, the mHesus_new device is the one we’re interested in. Then we scanned for dial-up networking services. We typed sdptool search —bdaddr 00:09:2D:2C:A2:1B DUN and pressed ENTER to receive the following output:
Searching for DUN on 00:09:2D:2C:A2:1B ...
Service Name: Dial-up Networking
Service RecHandle: 0x10007
Service Class ID List:
“Dialup Networking” (0x1103)
Protocol Descriptor List:
“L2CAP” (0x0100)
“RFCOMM” (0x0003)
Channel: 4
Language Base Attr List:
code_ISO639: 0x656e
encoding: 0x6a
base_offset: 0x100
Profile Descriptor List:
“Dialup Networking” (0x1103)
Version: 0x0100
Pay attention to the first Protocol Descriptor List; you're interested in the channel it lists. In our example, this tells us that the handset we’re scanning has a dial-up networking service using channel 4. To set up the connection, we bound the tty device to a Bluetooth connection. First, we typed rfcomm bind rfcomm0 00:09:2D:2C:A2:1B 4 and pressed ENTER. Then we typed rfcomm, pressed ENTER, and received the following output:
rfcomm0: 00:09:2D:2C:A2:1B channel 4 clean
Set Up PPP
With Bluetooth connectivity established, we configured pppd. Create a file called /etc/ppp/peers/myisp that contains:
/dev/rfcomm0 115200
connect ‘/usr/sbin/chat -v -f /etc/ppp/chat-myisp’
crtscts
modem
noccp
defaultroute
noauth
ipcp-accept-remote
ipcp-accept-local
noipdefault
Also create a file /etc/ppp/chat-myisp with the following content:
ATZ OK
ATD*99# CONNECT
Finally, we asked the handset to make a connection. We typed pppd call myisp and pressed ENTER. Our screen reported Bluetooth activity, followed by ppp dialing our ISP. With this approach, we didn’t configure any authentication on our computer because our phone took responsibility for relaying our account and password.
This approach is useful for occasional dial-up access. If you frequently find yourself needing dial-up, you can bind to /dev/rfcomm0 persistently so that your configuration survives across reboots.
In case you want the Bluetooth connection to be handled automatically when it’s needed, be sure to run rfcomm release rfcomm0 as root. To ensure that rfcomm0 is always available for telephone connections, add the following to /etc/bluetooth/rfcomm.conf:
rfcomm0 {
bind yes;
device 00:09:2D:2C:A2:1B;
channel 4;
comment “ISP connection channel”;
}
Success!
You should now have the capability of connecting to the ’Net with your laptop even when there’s no wired infrastructure nearby or a Wi-Fi hotspot in sight. Keep an eye on your applicable billing rates; a connection like the one described is probably pricey. (Although the fees may still be comparable to many public Wi-Fi access points.) A Bluetooth connection likely resists tampering better than public Wi-Fi, too.
Also, working in this way can free you from dependence on the power grid: If you’re hiking or at a sporting event, you can quickly make a connection to the Internet and retrieve or upload information.
As we already mentioned, the major cellular providers also offer data plans in the United States that can significantly reduce your costs if you often need wireless connections. In fact, many people now only subscribe to a cellular provider, with no wired line for their voice communications. Because wireless data service providers have become so competitive, some computer users have only a wireless ISP, dispensing entirely with the “wires” common for connecting to the Internet. 
by Cameron Laird
Infinite Loop: Cell Phone Death
The Institute of Cancer Research and three British universities recently released the results of a study that found that cell phones don’t necessarily raise your risk for developing brain cancer. But don’t take that news as a free pass to start yapping away. England’s Transport Research Laboratory has found that your reaction time while driving and talking on your cell phone can be impaired by as much as 50%. In some instances, chatting and driving can be more dangerous than driving drunk.
news.bbc.co.uk/2/hi/health/4628914.stm
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