app doesn't recieve signal DeviceDisappeared

app doesn't recieve signal DeviceDisappeared

[Ilya Rubtsov]

Hi!

Excuse me for my English.

I need help with using Bluez and dbus. Here is my small program in Python:

------------

import dbus
import dbus.glib
import gobject

def device_found(addr, values):
	print 'Found:', addr

def device_disapp(addr):    
	print 'Disappeared:', addr

bus = dbus.SystemBus()
obj = bus.get_object('org.bluez', '/org/bluez/hci0')
adapter = dbus.Interface(obj, 'org.bluez.Adapter')
adapter.connect_to_signal('DeviceFound', device_found)
adapter.connect_to_signal('DeviceDisappeared', device_disapp)

adapter.StartDiscovery()

gobject.threads_init()
dbus.glib.init_threads()
main_loop = gobject.MainLoop()
main_loop.run()


-----------

And I have problem with DeviceDisappeared signal. I run program, then it 
finds my bluetooth enabled phone and prints it's address every ~10 
seconds (periodical discovery). Than I turn off bluetooth in phone, but 
Bluez doesn't send signal 'DeviceDisappeared', so program doesn't print 
"Disappeared: ...". What's wrong in my program? Do I have 
misunderstanding of Bluez Adapter API?

Re: app doesn't recieve signal DeviceDisappeared

[Marcel Holtmann]

Hi Ilya,

> I need help with using Bluez and dbus. Here is my small program in Python:
> 
> ------------
> 
> import dbus
> import dbus.glib
> import gobject
> 
> def device_found(addr, values):
> 	print 'Found:', addr
> 
> def device_disapp(addr):    
> 	print 'Disappeared:', addr
> 
> bus = dbus.SystemBus()
> obj = bus.get_object('org.bluez', '/org/bluez/hci0')
> adapter = dbus.Interface(obj, 'org.bluez.Adapter')
> adapter.connect_to_signal('DeviceFound', device_found)
> adapter.connect_to_signal('DeviceDisappeared', device_disapp)
> 
> adapter.StartDiscovery()
> 
> gobject.threads_init()
> dbus.glib.init_threads()
> main_loop = gobject.MainLoop()
> main_loop.run()
> 
> 
> -----------
> 
> And I have problem with DeviceDisappeared signal. I run program, then it 
> finds my bluetooth enabled phone and prints it's address every ~10 
> seconds (periodical discovery). Than I turn off bluetooth in phone, but 
> Bluez doesn't send signal 'DeviceDisappeared', so program doesn't print 
> "Disappeared: ...". What's wrong in my program? Do I have 
> misunderstanding of Bluez Adapter API?

this might be a bug. Not many applications are actually making full use
of the DeviceDisappeared signal. Please run dbus-monitor and check if it
is really not present.

On another note, you can _NOT_ hardcode /org/bluez/hci0 path in your
apps. Nowadays they are totally random. Use FindAdapter() instead.

Regards

Marcel

Re: app doesn't recieve signal DeviceDisappeared

[Ilya Rubtsov]

Marcel Holtmann пишет:
> Hi Ilya,
>
>   
>> I need help with using Bluez and dbus. Here is my small program in Python:
>>
>> ------------
>>
>> import dbus
>> import dbus.glib
>> import gobject
>>
>> def device_found(addr, values):
>> 	print 'Found:', addr
>>
>> def device_disapp(addr):    
>> 	print 'Disappeared:', addr
>>
>> bus = dbus.SystemBus()
>> obj = bus.get_object('org.bluez', '/org/bluez/hci0')
>> adapter = dbus.Interface(obj, 'org.bluez.Adapter')
>> adapter.connect_to_signal('DeviceFound', device_found)
>> adapter.connect_to_signal('DeviceDisappeared', device_disapp)
>>
>> adapter.StartDiscovery()
>>
>> gobject.threads_init()
>> dbus.glib.init_threads()
>> main_loop = gobject.MainLoop()
>> main_loop.run()
>>
>>
>> -----------
>>
>> And I have problem with DeviceDisappeared signal. I run program, then it 
>> finds my bluetooth enabled phone and prints it's address every ~10 
>> seconds (periodical discovery). Than I turn off bluetooth in phone, but 
>> Bluez doesn't send signal 'DeviceDisappeared', so program doesn't print 
>> "Disappeared: ...". What's wrong in my program? Do I have 
>> misunderstanding of Bluez Adapter API?
>>     
>
> this might be a bug. Not many applications are actually making full use
> of the DeviceDisappeared signal. Please run dbus-monitor and check if it
> is really not present.
>   
I run 'dbus-monitor --system'. Now I'm sure there are no 
DeviceDisappeared signal.
Besides, I found that the adapter's Discovering property changes to True 
only _right before_ any device is found. If there are no devices in the 
field, this property will be False permanently.

I use BlueZ 4.12. I understand that before reporting any bug I should 
update my system with the lastest versions of packages, so if this bug 
was fixed between 4.12 an current 4.27 version - excuse me and sorry for 
disturbing.
> On another note, you can _NOT_ hardcode /org/bluez/hci0 path in your
> apps. Nowadays they are totally random. Use FindAdapter() instead.
>
>   
Now I use this method instead of hardcoding paths. Thanks!

Re: app doesn't recieve signal DeviceDisappeared

[Tom Patzig]

Hi,

>> this might be a bug. Not many applications are actually making full use
>> of the DeviceDisappeared signal. Please run dbus-monitor and check if it
>> is really not present.
I also recognized, that the signal DeviceDisappeared never gets thrown.
I need this Signal for KBlueLock (Screen lock, when your BT device
disappeares)
Right now i have located the problem a little deeper and did some tests.
I am using bluez-4.27 and use the test-discovery script in the test
directory. I expanded the testscript, to also listen for the
DeviceDisappeared Signals.

With a normal discovery, the signal gets never thrown (dbus-monitor).
And the curious thing is, that the 'Discovering' value always switches
between true and false ... so the discovery gets enabled and disabled
automatically. But jhe told me, this is intended to provide a
PeriodicDiscovery.

In adapter.c there is a function 'void adapter_set_state(struct
btd_adapter *adapter, int state)'. This function anyhow clears the List
with out of reach (oor) devices, depending on the discovery state.
If i comment out this if clause 'if (!discov_active &&
adapter->oor_devices)' to not free the oor device list, the Signal gets
thrown properly.
It gets thrown only once and the list of oor devices is also freed after
that (dont know where).
So my guess is, that the 'discov_active' boolean is set wrong (?), so
that this if clause is reached, but it should not.

This variable gets set depending on macros PERIODIC_INQUIRY and
STD_INQUIRY. What are these ?
So maybe the state is set wrong, but i do not know what the state should be.

Also strange is, that this DeviceDisappeared signal (with commented out
freeing of the oor list) only works, if more than one devices are in the
area. Because of the automatic stop/start of the 'Discovering' value. If
your one and only device gets disappeared the 'Discovering' value
switches to false and never starts searching again ( so it does not
recognize, that the device disappeared). The Discovery starts again,
when you device is visible again ...

I hope this helps, to find the problem.
I would also fix it, but i do not know which discovery state must be set
and which not, and when the oor list has to be freed and when not.

Regards,

Tom

Re: app doesn't recieve signal DeviceDisappeared

[Luiz Augusto von Dentz]

Hi Tom,

It should've been fixed now. Note that you only got those signals
while a discovery session is active (someone called
Adapter.StartDiscovery()).

--=20
Luiz Augusto von Dentz
Engenheiro de Computa=E7=E3o

Re: app doesn't recieve signal DeviceDisappeared

[Tom Patzig]

Hi,
> It should've been fixed now. Note that you only got those signals
> while a discovery session is active (someone called
> Adapter.StartDiscovery()).
>   
Thanks a lot. Works great.
Now i just need to wait for the next bluez release, to make use of it in
KBlueLock :)

Tom