Re: [Bluez-devel] multiple rfcomm listeners

[Marcel Holtmann <marcel@holtmann.org>]

Hi Peter,

> > I've heard that bluetooth clients are supposed to check for the SP
> > channel via sdp on every connect, but bluez doesn't do that in its
> > rfcomm bindings, eh? Do other devices check the channel only when pairing?
> This behaviour is completly implementation depended. The Widcom stack and
> even some other implementaions do request the server channel number for a
> service just before connection setup. Other implementations just store the
> server channel during pairing. The SDP variant has the problem that it is
> not realy possible to distinguish between two identical services which
> only have different server channels, e.g. many mobile phones and some
> other devices offer two SPP channels. With the SDP variant it is likely
> that you connect to the wrong service.
> The pairing variant has the drawback that you can not connect to a service
> anymore if its server channel changes dynamicly. This again is
> implementation depoendent on the client side. However, most devices I'm
> aware off use fixed server channels.

this is a problem with the Bluetooth specification and its qualication.
The SDP defines a time-to-live for the service record, but nobody uses
it. However I can remember what's the default behavior if this attribute
doesn't exists.

Regards

Marcel




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