Exchanging data over Bluetooth Classic

Exchanging data over Bluetooth Classic

[Dario Teixeira]

Hi,

Here's the situation: I want to use a smart phone to communicate with
a small embedded device (ED).  Unfortunately the ED is running a very
old kernel (3.10.93) which does not support Bluetooth Low Energy.
Therefore, if I am to use Bluetooth it will have to be BT Classic.

The communication is pretty straightforward: just a couple of RPC
calls using JSON.  Both the requests and the replies are reasonably
short.  The entire exchange can be summarised as follows:

  Phone: Here's request #1 (JSON text).
  ED: Okay, here's reply #1 (JSON text).
  Phone: Here's request #2 (JSON text).
  ED: Okay, here's reply #2 (JSON text).

Now, I have a couple of related questions:

a) I presume there's no other option than using RFCOMM, right?

b) I know that the first Google hit for "Bluetooth programming"
    is hopelessly out of date [1], because Bluez now uses DBus.
    However, where's the Bluez documentation for RFCOMM via DBus?
    I could only find this page for Bluez documentation [2],
    but RFCOMM is not mentioned.

Thanks in advance for your time!
Best regards,
Dario Teixeira

[1] https://people.csail.mit.edu/albert/bluez-intro/
[2] http://git.kernel.org/cgit/bluetooth/bluez.git/tree/doc

Re: Exchanging data over Bluetooth Classic

[Marcel Holtmann]

Hi Dario,

> Here's the situation: I want to use a smart phone to communicate with
> a small embedded device (ED).  Unfortunately the ED is running a very
> old kernel (3.10.93) which does not support Bluetooth Low Energy.
> Therefore, if I am to use Bluetooth it will have to be BT Classic.
> 
> The communication is pretty straightforward: just a couple of RPC
> calls using JSON.  Both the requests and the replies are reasonably
> short.  The entire exchange can be summarised as follows:
> 
> Phone: Here's request #1 (JSON text).
> ED: Okay, here's reply #1 (JSON text).
> Phone: Here's request #2 (JSON text).
> ED: Okay, here's reply #2 (JSON text).
> 
> Now, I have a couple of related questions:
> 
> a) I presume there's no other option than using RFCOMM, right?
> 
> b) I know that the first Google hit for "Bluetooth programming"
>   is hopelessly out of date [1], because Bluez now uses DBus.
>   However, where's the Bluez documentation for RFCOMM via DBus?
>   I could only find this page for Bluez documentation [2],
>   but RFCOMM is not mentioned.

you can use L2CAP or RFCOMM sockets to transfer data. Or you can use OBEX as provided by obexd if it is more file related transfer you are after.

Regards

Marcel

Re: Exchanging data over Bluetooth Classic

[Dario Teixeira]

Hi,

> you can use L2CAP or RFCOMM sockets to transfer data. Or you can use
> OBEX as provided by obexd if it is more file related transfer you are
> after.

Thanks for the reply. What is the most convenient way to programatically
use L2CAP or RFCOMM? There is one guide [1], but I reckon it's out of 
date
since Bluez made the transition to DBUS.  I heard it's possible to 
create
a character device for RFCOMM sockets; using them programatically them
reduces to the usual open/read/write/close of a file descriptor. Is this
still possible? (Mind you, Bluez docs are laconic in the extreme!)

Best regards,
Dario Teixeira

[1] https://people.csail.mit.edu/albert/bluez-intro/