BlueZ5: Event when inbound pairing is complete

Question

I'm writing a C++-application which manages Bluetooth connections for an embedded device. I talk to BlueZ5 via D-Bus under Linux.

As first steps in implementing inbound pairing I did the following:

• Register "NoInputNoOutput" agent via the AgentManager1 interface
• set pairable on and pairable timeout as well as discoverable on and discoverable timeout via the Adapter1 interface

Now I need an event that tells me that a new device was paired, so I can trust it and accept SPP connections. But I couldn't find such an event in the spec yet (https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc).

Is there such an event? It seems it as bluetoothctl emits a message like

[NEW] Device 44:55:66:11:22:33 Foo Bar

as soon as device is paired...

Can somebody tell me which event I have to listen for?

Or do I have to poll? I don't think bluetoothctl polls as it reacts really quickly.

Answer 1

From here

boolean Connected [readonly]

Indicates if the remote device is currently connected. A PropertiesChanged signal indicate changes to this status.

When the new device is added, InterfaceAdded signal is broadcasted on interface=org.freedesktop.DBus.ObjectManager. See the below signal captured using dbus-monitor. Check for the property Connected.

signal time=1558128293.155096 sender=:1.2 -> destination=(null destination) serial=65 path=/; interface=org.freedesktop.DBus.ObjectManager; member=InterfacesAdded
   object path "/org/bluez/hci0/dev_F0_D7_AA_AA_0C_41"
   array [
      dict entry(
         string "org.freedesktop.DBus.Introspectable"
         array [
         ]
      )
      dict entry(
         string "org.bluez.Device1"
         array [
            dict entry(
               string "Address"
               variant                   string "F0:D7:AA:AA:0C:41"
            )
            dict entry(
               string "Name"
               variant                   string "Moto"
            )
            dict entry(
               string "Alias"
               variant                   string "Moto"
            )
            dict entry(
               string "Class"
               variant                   uint32 5898764
            )
            dict entry(
               string "Icon"
               variant                   string "phone"
            )
            dict entry(
               string "Paired"
               variant                   boolean false
            )
            dict entry(
               string "Trusted"
               variant                   boolean false
            )
            dict entry(
               string "Blocked"
               variant                   boolean false
            )
            dict entry(
               string "LegacyPairing"
               variant                   boolean false
            )
            dict entry(
               string "Connected"
               variant                   boolean true
            )
            dict entry(
               string "UUIDs"
               variant                   array [
                  ]
            )
            dict entry(
               string "Adapter"
               variant                   object path "/org/bluez/hci0"
            )
         ]
      )
      dict entry(
         string "org.freedesktop.DBus.Properties"
         array [
         ]
      )
   ]

If device is already added then you get PropertiesChanged signal on interface=org.freedesktop.DBus.Properties. See below capture, its a log on disconnect, but the one above could help you to receive signal when device is connected.

signal time=1558128303.204016 sender=:1.2 -> destination=(null destination) serial=71 path=/org/bluez/hci0/dev_F0_D7_AA_AA_0C_41; interface=org.freedesktop.DBus.Properties; member=PropertiesChanged
   string "org.bluez.Device1"
   array [
      dict entry(
         string "Connected"
         variant             boolean false
      )
   ]
   array [
   ]