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From: Barry Byford <31baz66@gmail.com> Date: Mon, 12 Sep 2016 20:37:59 +0100 Message-ID: Subject: Re: Query BLE connected status? To: Travis Griggs Cc: Bluez mailing list Content-Type: text/plain; charset=UTF-8 Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hello Travis, On 12 September 2016 at 16:52, Travis Griggs wrote= : > >> On Sep 7, 2016, at 3:19 PM, Barry Byford <31baz66@gmail.com> wrote: >> >> Hi Travis, >> >> On 7 September 2016 at 22:14, Travis Griggs wro= te: >> >>> What is the difference between and adapter and device in the lingo here= ? >> As you correctly identify the adapter is the bluetooth dongle on your Li= nux SBC >> The device is the remote Bluetooth device that you are connecting to. > > Aha! Lightbulb moment there for me. Thank you so much! Excellent news! Glad it helped >>> >>> # ./connected >>> (no output) >>> >>> # ./connected >>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 1 >>> >>> # ./connected >>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0 >>> >>> # ./connected >>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0 >>> >>> ./connected >>> /org/bluez/hci0/dev_49_7C_73_51_21_1E Connected: 0 >>> /org/bluez/hci0/dev_41_7B_77_4F_E4_AA Connected: 1 >>> >> >> If looks like your iOS app is creating a different device address each >> time it is started. I see this on a few of the Android apps that I use >> that emulate things like heart rate monitors or battery services. >> >> >>> Is there a way to register something more event based so I could be not= ified when it changes? >> >> Yes there is. You can connect to the 'PropertiesChanged' signal on the >> 'org.bluez.Device1' interface. >> I've done a piece of code that demonstrates this. I've used an Android >> app to test it. To get around the issue of it having a different >> address each time I switch the app on, I've left the app running and >> then in a separate window on my SBC I use Bluetoothctl to do the >> connect/disconnect commands. >> >> Hopefully the email tool will not mangle the formatting of this code too= much: >> >> #!/usr/bin/env python3 >> import dbus >> import dbus.mainloop.glib >> from gi.repository import GLib >> >> dbus.mainloop.glib.DBusGMainLoop(set_as_default=3DTrue) >> mainloop =3D GLib.MainLoop() >> >> >> def get_iface_prop(iface, prop): >> response =3D {} >> bus =3D dbus.SystemBus() >> mng =3D dbus.Interface(bus.get_object('org.bluez', '/'), >> 'org.freedesktop.DBus.ObjectManager') >> for path, ifaces in mng.GetManagedObjects().items(): >> if iface in ifaces: >> response[path] =3D ifaces[iface][prop] >> return response >> >> class Device: >> def __init__(self, device_path): >> self.bus =3D dbus.SystemBus() >> self.device_path =3D device_path >> self.device_obj =3D self.bus.get_object('org.bluez', device_path) >> device_props =3D dbus.Interface(self.device_obj, dbus.PROPERTIES_= IFACE) >> device_props.connect_to_signal('PropertiesChanged', >> self.on_prop_changed) >> >> def on_prop_changed(self, iface, changed_props, invalidated_props): >> if 'org.bluez.Device1' in iface: >> if 'Connected' in changed_props: >> print('{0} is now {1}'.format(self.device_path, >> changed_props['Connected'])) >> >> >> if __name__ =3D=3D '__main__': >> for k, v in get_iface_prop('org.bluez.Device1', 'Connected').items(): >> print('{0} is {1}'.format(k, v)) >> Device(k) >> >> mainloop.run() >> >> My test output looked like this: >> >> ./connected_devices.py >> /org/bluez/hci0/dev_E8_A9_41_CE_31_5A is 0 >> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is 1 >> /org/bluez/hci0/dev_B0_B4_48_BE_5D_83 is 0 >> /org/bluez/hci0/dev_F7_17_E4_09_C0_C6 is 0 >> /org/bluez/hci0/dev_8C_2D_AA_44_0E_3A is 0 >> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 0 >> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 1 >> /org/bluez/hci0/dev_5E_4B_97_7B_22_C3 is now 0 >> >> This was all done using BlueZ 5.40 with the experimental flag switched >> on. I hope that helps move things forward for you. > > Your code worked. Also good news! > But it seems that it only has a one a time pass to determine which remote= devices to register the property change. So for a given snapshot of curren= t devices, it can notify their state changes. But it won=E2=80=99t notice i= f a new object path shows up. True the code I gave as an example did not update if a device was added after initial invocation. You will need to look at the 'InterfacesAdded' signal to see when a device gets added. An example of how to do that would be: bus.add_signal_receiver(interfaces_added, dbus_interface=3D'org.freedesktop.DBus.ObjectMa= nager', signal_name=3D'InterfacesAdded') The interfaces_added function could then use the Device class we created previously to connect to the PropertiesChanged signal on that device to listen if it was connected or not. > > It seems to me though, that maybe I=E2=80=99m going about this wrong. I d= on=E2=80=99t care about the device identity, or which devices are connected= or not. What I really care about is if any device is connected to my app. = And maybe I have this (kind of indirectly). My characteristic will get a St= artNotify/StopNotify event on connect/disconnect edges. I can just use thos= e to keep track of when I=E2=80=99m active or not. Not sure the StopNotify is a reliable way to detect that there has been a disconnect. The full code that I used to test what I had written above was: #!/usr/bin/env python3 import dbus import dbus.mainloop.glib from gi.repository import GLib dbus.mainloop.glib.DBusGMainLoop(set_as_default=3DTrue) mainloop =3D GLib.MainLoop() def interfaces_added(path, interfaces): if 'org.bluez.Device1' in interfaces: print('Device added at {}'.format(path)) Device(path) def get_iface_prop(iface, prop): response =3D {} bus =3D dbus.SystemBus() mng =3D dbus.Interface(bus.get_object('org.bluez', '/'), 'org.freedesktop.DBus.ObjectManager') bus.add_signal_receiver(interfaces_added, dbus_interface=3D'org.freedesktop.DBus.ObjectMa= nager', signal_name=3D'InterfacesAdded') for path, ifaces in mng.GetManagedObjects().items(): if iface in ifaces: response[path] =3D ifaces[iface][prop] return response class Device: def __init__(self, device_path): self.bus =3D dbus.SystemBus() self.device_path =3D device_path self.device_obj =3D self.bus.get_object('org.bluez', device_path) device_props =3D dbus.Interface(self.device_obj, dbus.PROPERTIES_IF= ACE) device_props.connect_to_signal('PropertiesChanged', self.on_prop_changed) def on_prop_changed(self, iface, changed_props, invalidated_props): if 'org.bluez.Device1' in iface: if 'Connected' in changed_props: print('{0} is now {1}'.format(self.device_path, changed_props['Connected'])) if __name__ =3D=3D '__main__': for k, v in get_iface_prop('org.bluez.Device1', 'Connected').items(): print('{0} is {1}'.format(k, v)) Device(k) mainloop.run() I removed all the devices before I started running the script so no devices were reported at invocation. Again, I had a separate window doing the scanning and connecting which resulted in the following output: $ ./connect_devices.py Device added at /org/bluez/hci0/dev_48_C0_7B_35_98_A5 /org/bluez/hci0/dev_48_C0_7B_35_98_A5 is now 1 /org/bluez/hci0/dev_48_C0_7B_35_98_A5 is now 0 Device added at /org/bluez/hci0/dev_60_06_57_DD_4C_2F Device added at /org/bluez/hci0/dev_54_1F_46_F1_AA_32 /org/bluez/hci0/dev_54_1F_46_F1_AA_32 is now 1 /org/bluez/hci0/dev_54_1F_46_F1_AA_32 is now 0