Handle a device already being connected with the BlueZ Dbus backend

CHANGELOG.rst

@@ -20,6 +20,7 @@ Changed
   To use the cache, call ``connect`` and ``get_services`` with the ``dangerous_use_bleak_cache``
   argument to avoid services being resolved again.
 * The BlueZ D-Bus backend now uses ``dbus-fast`` instead of ``dbus-next`` which significantly improves performance.
+* The BlueZ D-Bus backend will not avoid trying to connect to devices that are already connected.
 
 Fixed
 -----

bleak/backends/bluezdbus/client.py

@@ -155,16 +155,25 @@ def on_value_changed(char_path: str, value: bytes) -> None:
 
         try:
             try:
-                async with async_timeout.timeout(timeout):
-                    reply = await self._bus.call(
-                        Message(
-                            destination=defs.BLUEZ_SERVICE,
-                            interface=defs.DEVICE_INTERFACE,
-                            path=self._device_path,
-                            member="Connect",
+                #
+                # The BlueZ backend does not disconnect devices when the
+                # application closes or crashes. This can cause problems
+                # when trying to reconnect to the same device. To work
+                # around this, we check if the device is already connected.
+                #
+                # For additional details see https://github.com/bluez/bluez/issues/89
+                #
+                if not manager.is_connected(self._device_path):
+                    async with async_timeout.timeout(timeout):
+                        reply = await self._bus.call(
+                            Message(
+                                destination=defs.BLUEZ_SERVICE,
+                                interface=defs.DEVICE_INTERFACE,
+                                path=self._device_path,
+                                member="Connect",
+                            )
                         )
-                    )
-                assert_reply(reply)
+                    assert_reply(reply)
 
                 self._is_connected = True
 

bleak/backends/bluezdbus/manager.py

@@ -597,6 +597,21 @@ def get_device_name(self, device_path: str) -> str:
         """
         return self._properties[device_path][defs.DEVICE_INTERFACE]["Name"]
 
+    def is_connected(self, device_path: str) -> bool:
+        """
+        Gets the value of the "Connected" property for a device.
+
+        Args:
+            device_path: The D-Bus object path of the device.
+
+        Returns:
+            The current property value.
+        """
+        try:
+            return self._properties[device_path][defs.DEVICE_INTERFACE]["Connected"]
+        except KeyError:
+            return False
+
     async def _wait_condition(
         self, device_path: str, property_name: str, property_value: Any
     ) -> None: