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Bluetooth - Explained to a Finer Level

Ravi Agrawal

I have always been fascinated by wireless technology ranging from Infrared to Wimax. Bluetooth comes next to Infrared (in terms of distance of operation) and is commonly used in gadgets like Cellphones, PDAs and Computers for the exchange of Data. Since you are reading this, I assume you to be fairly acquainted with computers and such stuff. The basic advantage behind Bluetooth is that it always works. And when it doesn’t, well that’s why I am writing this Article.

Connecting via Bluetooth:

The primary way of connecting to any Bluetooth device always remains the same. Both the devices turn on Bluetooth Radio & set themselves to be Discoverable. Suppose we want to pair 2 Devices. Then, following will be the process to pair and share services on them.

Device A initiates a scan for new devices.
When Device B is listed (there can be more than one device listed if there are other Bluetooth devices in proximity of the scanning device), Device A sends out a “Request to Pair” message to Device B.
Device B responds to Device A to enter a Passcode.
User on Device A receives a Dialog box prompting to enter a Passcode where it is entered and sent back to Device B. The Passcode is mutually agreed between the two users. It can be a 4 digit number or any alphanumeric code too. I generally use 1234.
User on Device B also receives a Dialog box prompting to enter a Passcode where it is entered. It should be the same which was entered in Device A, else pairing will fail.
Both the Device Users get a “Pairing completed” message and can use the services offered by the devices.

Three requirements are necessary for initial configuration, connection and pairing between Bluetooth devices-

Bluetooth must be switched On.
Device must be set to Discoverable (not Hidden).
The mutually accepted pass code must be the same on both devices to be paired.

After that, Users can authorize the Devices to connect automatically, so that pairing is not required every time the devices want to communicate. For additional security, they can set their Devices to “Hidden”, which will allow them to communicate but won’t allow foreign Devices to see them.

Client Server Relationship:

Paired devices work in a Client – Server fashion. One device provides the Services (Server) and the other accesses the services (Client). However it is possible that at one particular time a Device is acting like a Server & at another time the same Device is behaving like a Client.


Mutual pairing is not enough. Advanced Bluetooth Devices come with multiple services. You have to specifically connect to a service on the Device to access it after Pairing. Suppose you have successfully installed a Bluetooth Adapter on your PC. This adapter can act like a Server giving out many services depending on the Drivers installed on your Operating System. For example, My Device offers Five Services (See image).
Services on PCThis is what My PC has to offer. The other device must be capable of retrieving those services in Client mode & if it doesn’t support that, it won’t be able to use it. The basic idea is both devices must support the same set of services for proper communication. My phone which is paired to the PC Bluetooth Adapter offers three Services (See image).
Sevices on PhoneIn order to successfully use the services of my Phone, my PC’s Bluetooth Adapter must be able to access those Services as a Client but it only supports two of them which are-

Dial up Networking
File Transfer

In order to successfully use the services of my PC’s Bluetooth Adapter, my Phone must be able to access those Services as a Client but it only supports one of them which is-

Object Push

So even though many services are there, it is not possible to use them as anyone would generally expect. This brings us to one big level of confusion. Services that can be accessed as a Client by a Bluetooth device need not be the same as those are offered by it. You have to know your device well (or consult its documentation) in order to understand what services it can access as a Client.

Bluetooth Dongles and Drivers:

Bluetooth hardware comes in more flavors than you would expect. Most commonly, it is in the form of a USB Dongle (that may have an LED to indicate On status) or it may be embedded on the motherboard itself (much like your LAN card). Like all other devices in Windows, Bluetooth Adapters (or Dongles) also come with their own set of drivers. Commonly used drivers are from Bluesoleil, Widcomm, HP and Microsoft. Beware that drivers for one Dongle are specific to its manufacturer. A Bluetooth adapter made to work with Bluesoleil Drivers may go undetected when you try to make it work with Microsoft Drivers. Microsoft includes drivers for Bluetooth in Windows XP that may or may not work for you. They are generally allowed to be over-ridden by the Custom Drivers installed by you like the above mentioned.

Other Cases:

There are devices like Headphones that don’t have an Interface like a keypad to Enter a Passcode. These devices are shipped with a default Passcode of 0000 & are always discoverable (cannot be set to Hidden). However there are indications by LEDs on these devices which may blink in a particular pattern to indicate a “Scan going on” or “Successful Pair created”. Since they come with only one service, there is no need to connect to a service & they start playing straight away after the Pairing process has been completed.

Helpful Stuff:

Install all your related Drivers. For example, My Nokia N73 phone came with a Software called Nokia PC suite. Installation of it prior to Bluetooth drivers made the connection seamless with my Phone.

Get latest updated Drivers. A previous version of Bluetooth Drivers would not connect to my phone for unknown reasons.
In case you are stuck up with a Dialup Connection to your phone giving you some sort of PPP error try this -- Control Panel >> Phone and Modem Options >> Modems Tab >> Your Bluetooth modem >>  select it & click the Properties button >> Advanced Tab >> Under extra initialization commands enter the following string at+cgdcont=1,"ip","bsnlnet","",0,0 where bsnlnet is the name of your Internet Access Point. Ok out everything & you should connect successfully. Make sure the Phone Number you are dialing in your Connection is *99# See Image.
Access Point Settings in Modem
Speed up your Internet connection in case you are using a Bluetooth modem to connect. It applies to Windows XP only --
In Device Manager expand Modems and select your Bluetooth Modem >> Right Click for Properties >> Modem tab. Note down the Port number Listed after Port. It would be COMx where x is an integer (6, 7, 13 or something like that). Set the Port speed to 115200 in the Same Tab. Close the Modem properties box. Expand Ports (COM & LPT) in Device Manager. Select the Bluetooth Serial Port (COMx) related to your modem >> Right Click for Properties >> Port Settings >> Increase the Value of Bits per Second to 115200. In case you were using a Bluetooth Modem which worked slowly, you should note an increase in speed. Changes are applied immediately and there is no need to reboot. Don't try setting the maximum modem speed to greater than 115200 (128000 or higher) as then you will face random disconnects resulting in an unstable connection.
Just in case you have paired your device that worked earlier and it does not work now, delete it from the list of paired devices and pair it again.
When scanning, if your device goes undetected despite taking all the right measures, try moving the device really very close (within a few centimeters) to the other device. Once found and paired, you can take it further away. Scanning for new devices helps a lot, when the device to be searched is in very close proximity to the device doing the scan.

Helpful Links:

See this Question on Experts Exchange explaining “How to connect a Device with Bluetooth with Screenshots
Just in case you are stuck trying to get your Bluetooth work, see this link from Microsoft.
How to setup an internet connection on Symbian phones using Bluetooth . This will show you how to use Bluetooth as a Wifi Adapter  (just in case your Symbian [Nokia and the like] phone doesn't have one) to access Internet using the Bluetooth Adapter of your PC as an Access Point.
Bluetooth technology has gone really far to make your life easy. See this link which shows a Virtual Full Size Keyboard that can be used via your Handheld, just as if it was connected to a physical Keyboard.
This link also has good information about Bluetooth.

Limitations of Bluetooth Technology:

Only two Devices can communicate at a time. Once a Device is engaged in a Bluetooth session with some other Device, it cannot start communication with a third Device.
Speed of transmission is really slow. Mutual File transfers in Windows take place at 55-60 KB/s, means it takes around 90 seconds to transfer a 5 MB file  between 2 Devices via Bluetooth.
A small operating Range of 10 meters or 35 feet.
Drain on Battery like all wireless equipment do.
A bottleneck for devices using HSDPA technology (7.2 mbps) to connect to your PC via bluetooth (2.1 mpbs)

Final Words:

May it interest you that this is my fifth article on Experts Exchange. The other four are --

Applications worthy of being in a Windows Techie Toolkit
Troubleshooting and repairing misbehaving Peripherals in Windows using the Device Manager
Putting Windows Explorer on Steroids
Dumping Windows Default Applications for Better Ones (Part One)

Was the read worth it? May I request you the reader to kindly click the Small Blue "Yes" button at the End of this Article, where it states "Was this article helpful?", if you really did find it helpful. A "No" is also welcome, so that at least I will know that you got through the stuff I wrote.

Please post comments, so that I may improve on it further. Your input will help me to improve and benefit all future readers.

Ravi Agrawal

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