Re: [Bluez-users] UDP and TCP packets across Bluez connections?

[Marcel Holtmann <marcel@holtmann.org>]

Hi,

> I have an emebdded Linux app that currently listens on a socket that
> receives messages from multiple interfaces (e.g. ethernet, USB with
> RNDIS, wireless). I want to add Bluetooth support. 
> 
> My question: Do Bluez interfaces to Bluetooth devices act like any
> other IP interface? 
> 
> I found example source code on the internet of sockets being opened
> with AF_BLUETOOTH as the socket domain (i.e. the first argument to the
> socket call). Does one have to always do it that way in order to
> receive inbound messages on a Bluetooth interface? 
> 
> I came across text that makes it sound like one uses L2CAP in place of
> UDP and RFCOMM in place of TCP. 
> http://people.csail.mit.edu/albert/bluez-intro/x95.html 
> 
> http://bluez.sourceforge.net/contrib/HOWTO-PAN 
> 
> So then is it not possible to do TCP/IP across Bluetooth connections?
> Does one need to write application level code that is different for
> Bluetooth as compared to ethernet/USB/wireless? 

so first of all. The socket interface doesn't mean IP. It is a generic
way of using network protocols. And network protocols doesn't mean IP
only. There are more network protocols than you can think of.

> Also, if one can do TCP/IP over Bluetooth from Linux then does Windows
> recognize incoming TCP and UDP packets without loading a special
> driver on Windows? Currently with USB one uses RNDIS on Windows and an
> RNDIS equivalent driver configuration on Linux. Then Windows and Linux
> can talk. But to do TCP/IP between Linux and Windows over Bluetooth
> what does one do? 
> 
> Or if there is not real TCP/IP support with Bluetooth does Windows
> understand RFCOMM and L2CAP? 

If you wanna have TCP then you can do Ethernet over Bluetooth which is
done by PAN over BNEP. And that would interact with Windows or any other
OS for that matter.

> Also, is there some sort of authoritative write-up on a web page
> somewhere about TCP/IP on Bluetooth? I've Googled up read probably 100
> web pages looking for better info and haven't found it.

The first thing that you should read is a Bluetooth introduction that
explains the various protocol layers that can be used for various tasks.

Regards

Marcel



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