[Bluez-devel] decoding RFCOMM on hcidump -X -V

[Bluez-devel] decoding RFCOMM on hcidump -X -V

[Jeff Wilson]

Hi Marcel, hi list,

Does Bluetooth's RFCOMM protocol have ACKs and a sliding window, like
TCP?  Is it possible for a sending application to block on send when
sending a large payload to a slow reading application?

I'm trying to debug a program I wrote using
socket(PF_BLUETOOTH,SOCK_STREAM,BTPROTO_RFCOMM). Where can I learn
more about decoding the output of `hcidump -X -V` especially as it
applies to traffic crossing this RFCOMM socket?  I am particularly
interested in what to look for when chasing flow control and TCP-like
reliability.

Thanks for your time,

       Jeff


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Re: [Bluez-devel] decoding RFCOMM on hcidump -X -V

[Marcel Holtmann]

Hi Jeff,

> Does Bluetooth's RFCOMM protocol have ACKs and a sliding window, like
> TCP?  Is it possible for a sending application to block on send when
> sending a large payload to a slow reading application?

the RFCOMM is using flow control only. There is no sliding window and
thus no real ACK mechanism.

> I'm trying to debug a program I wrote using
> socket(PF_BLUETOOTH,SOCK_STREAM,BTPROTO_RFCOMM). Where can I learn
> more about decoding the output of `hcidump -X -V` especially as it
> applies to traffic crossing this RFCOMM socket?  I am particularly
> interested in what to look for when chasing flow control and TCP-like
> reliability.

Since RFCOMM also has an MTU, you will see the packets going over the
air and the granted credits from each side.

Regards

Marcel




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