Understanding GUID(UUID) in low level Bluetooth programming under Windows.

Question

So I dove deep in the world of programming, upto the low level hardwares to make use of the bluetooth socket in Windows.

Then I came across the word 'GUID' so many times. According to what I understood from the articles,

"The UUID is used for uniquely identifying information. It identifies a particular service provided by a Bluetooth device."

Now I am confused about on which side I should provide the GUID ? In client or server? Or do they (server and client) both require to have a GUID address to start up bluetooth communication ?

And another question I have in my mind is that , can GUID be any random instead some already defined GUID s on internet ?

And are "Service Class Id" and "GUID" same in Windows bluetooth programming ?

NB: GUID and UUID , both terms are almost same from the perspective of Bluetooth programming in Windows.

Answer 1

Answer to the last question

In Windows Bluetooth programming, the term "Service Class ID" (SCID) is used instead of "GUID" to refer to the same concept. The SCID is a 128-bit value that identifies a Bluetooth service. Therefore, in Windows Bluetooth programming, the terms "SCID" and "GUID" are used interchangeably.

I asked my brother about this fact cause he had done this earlier

Answer 2

Snehil Can I use any random UUID for windows bluetooth server advertisement?
Or I am bound to use the system UUID?

Answer 3

[B.S.] BITTU well you are not bound to use the system UUID when broadcasting a Bluetooth service in Windows.
You can use any uuid that is unique to your application.
but its important to ensure that the uuid is truly unique to avoid conflicts with other services.

Answer 4

Snehil

Can I use UuidFromString() function to create a UUID from string... will it do?

And brother ,this thread is going to be long as I have a lot of questions about bluetooth socket programming under windows so, all I wish is your company and help. I hope you won't mind.

Answer 5

[B.S.] BITTU
well you can use that but from this I came to know that you are using c++ to code it that means it's particularly for Windows only

I'm ready to have conversations but I'm not that knowledgeable in this field

Answer 6

Yes I am doing it in C++ and particularly targeting windows for now.

So I have created a server and advertised it with a random UUID

using WSASetService: like this link below
https://stackoverflow.com/questions/70475988/how-to-use-wsasetservice-to-advertise-bluetooth-service-using-wsaqueryset-struct

On client side
I used

SOCKADDR_BTH BLTHADDR;

BLTHADDR.addressFamily = AF_BTH;
BLTHADDR.port = BT_PORT_ANY
BLTHADDR.btAddr = [remote addr]
BLTHADDR.serviceClassId = [UUID_OF_SERVER]

After Having run this code with,

connect(socket, (sockaddr*)&BLTHADDR, sizeof(BLTHADDR)),

then connect returns 10060 (Timed Out)

Can you guess what is possibly going wrong?

Both my laptops are paired already.

Answer 7

[B.S.] BITTU
Check if there is a firewall or antivirus software that is blocking the connection

or

check btAddr member of SOCKADDR_BTH is set to the correct Bluetooth address of the server device

well I can guess not more than these
I'm not that experienced in these so maybe you should ask some experienced people over here cause I read only some parts of this section

Answer 8

It was the client side firewall that was blocking the socket and thanks a lot my friend Snehil You are a life saver

Answer 9

[B.S.] BITTU
happy to hear that I'm not noob in this 😂

Answer 10

Snehil
Well , I have got another question in mind.

I have read somewhere that some portion of GUID defines the type of service I am willing to use and
I have seen most of the bluetooth GUIDs to have a identical syntax like:

XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX

Where there are 5 segments separated by dashes. The first segment has 8 hexadecimal digits , next three segments have 4 hexadecimal digits and the last segment has 12 hexadecimal digits.

So do these segments denote or signify something about service it provides or it is just a random hexadecimal identifier ?

Answer 11

[B.S.] BITTU it's random and each segment has some specific function/use

Answer 12

Snehil Can you provide any link where the function of each segment is described?

I have found this:
https://learn.microsoft.com/en-us/windows-hardware/drivers/install/system-defined-device-setup-classes-available-to-vendors

But this doesn't describe functionality of each segment separately.

well, it also doesn't matter until I get my works done perfectly...

Answer 13

[B.S.] BITTU I don't know much about what each part does so I can't recommend
but I think that there might be some information about UUIDs on website:
https://www.bluetooth.com

Answer 14

Snehil

I am willing to connect my bluetooth earphones with my laptop using winsock.

So do you know in which mode are bluetooth earphones set by default ? Server or Client ?

And in which mode do they communicate , SOCK_STREAM or SOCK_DGRAM ?

Answer 15

[B.S.] BITTU in general Bluetooth earphones act like client as they initiate a connection to another device

generally communication mode depends on the specific protocol and profile that earphones uses

Answer 16

Snehil Do you have any good website for that ?

Answer 17

Snehil Thanks a lot friend for helping me out throughout this tough journey.

Answer 18

[B.S.] BITTU well website related to?
if completely about Bluetooth Core:
www.bluetooth.com/specificatons

Answer 19

Snehil Website related to how bluetooth earphones actually work?
Your link too is a good destination I think

Answer 20

https://community.nxp.com/pwmxy87654/attachments/pwmxy87654/wireless-connectivity/7638/1/Bluetooth%2520Low%2520Energy%2520Application%2520Developer%27s%2520Guide.pdf&ved=2ahUKEwi0raf9yaP-AhUahGMGHYuLAWsQFnoECBMQAQ&usg=AOvVaw0DEh7vkzTpEXozA-gny6xt

you can download a developer guide for that
source:google