diff --git a/.github/workflows/code-check.yml b/.github/workflows/code-check.yml
index b6cf8fd..021b1e4 100644
--- a/.github/workflows/code-check.yml
+++ b/.github/workflows/code-check.yml
@@ -14,6 +14,10 @@
   check:
     name: Check Code
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
+      fail-fast: false
 
     steps:
     - name: Check out from Git
diff --git a/.github/workflows/python-build-test.yml b/.github/workflows/python-build-test.yml
index c8a1031..4cc3e73 100644
--- a/.github/workflows/python-build-test.yml
+++ b/.github/workflows/python-build-test.yml
@@ -12,10 +12,10 @@
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        os: ['ubuntu-latest', 'macos-latest', 'windows-latest']
         python-version: ["3.8", "3.9", "3.10", "3.11"]
       fail-fast: false
 
@@ -41,6 +41,7 @@
       run: |
         inv build
         inv build.mkdocs
+
   build-rust:
     runs-on: ubuntu-latest
     strategy:
@@ -64,6 +65,8 @@
         with:
           components: clippy,rustfmt
           toolchain: ${{ matrix.rust-version }}
+      - name: Check License Headers
+        run: cd rust && cargo run --features dev-tools --bin file-header check-all
       - name: Rust Build
         run: cd rust && cargo build --all-targets && cargo build --all-features --all-targets
       # Lints after build so what clippy needs is already built
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 864fe69..57e682a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -39,10 +39,12 @@
         "libusb",
         "MITM",
         "NDIS",
+        "netsim",
         "NONBLOCK",
         "NONCONN",
         "OXIMETER",
         "popleft",
+        "protobuf",
         "psms",
         "pyee",
         "pyusb",
diff --git a/apps/console.py b/apps/console.py
index 0ea9e5b..9a529dd 100644
--- a/apps/console.py
+++ b/apps/console.py
@@ -1172,7 +1172,7 @@
             name = ''
 
         # Remove any '/P' qualifier suffix from the address string
-        address_str = str(self.address).replace('/P', '')
+        address_str = self.address.to_string(with_type_qualifier=False)
 
         # RSSI bar
         bar_string = rssi_bar(self.rssi)
diff --git a/apps/controller_info.py b/apps/controller_info.py
index 4707983..5be4f3d 100644
--- a/apps/controller_info.py
+++ b/apps/controller_info.py
@@ -63,7 +63,8 @@
         if command_succeeded(response):
             print()
             print(
-                color('Classic Address:', 'yellow'), response.return_parameters.bd_addr
+                color('Classic Address:', 'yellow'),
+                response.return_parameters.bd_addr.to_string(False),
             )
 
     if host.supports_command(HCI_READ_LOCAL_NAME_COMMAND):
diff --git a/apps/pandora_server.py b/apps/pandora_server.py
index b577f82..16bc211 100644
--- a/apps/pandora_server.py
+++ b/apps/pandora_server.py
@@ -3,7 +3,7 @@
 import logging
 import json
 
-from bumble.pandora import PandoraDevice, serve
+from bumble.pandora import PandoraDevice, Config, serve
 from typing import Dict, Any
 
 BUMBLE_SERVER_GRPC_PORT = 7999
@@ -29,12 +29,14 @@
         transport = transport.replace('<rootcanal-port>', str(rootcanal_port))
 
     bumble_config = retrieve_config(config)
-    if 'transport' not in bumble_config.keys():
-        bumble_config.update({'transport': transport})
+    bumble_config.setdefault('transport', transport)
     device = PandoraDevice(bumble_config)
 
+    server_config = Config()
+    server_config.load_from_dict(bumble_config.get('server', {}))
+
     logging.basicConfig(level=logging.DEBUG)
-    asyncio.run(serve(device, port=grpc_port))
+    asyncio.run(serve(device, config=server_config, port=grpc_port))
 
 
 def retrieve_config(config: str) -> Dict[str, Any]:
diff --git a/apps/speaker/speaker.py b/apps/speaker/speaker.py
index 1a1eac3..e451c04 100644
--- a/apps/speaker/speaker.py
+++ b/apps/speaker/speaker.py
@@ -195,7 +195,7 @@
         except HCI_StatusError:
             pass
         peer_name = '' if connection.peer_name is None else connection.peer_name
-        peer_address = str(connection.peer_address).replace('/P', '')
+        peer_address = connection.peer_address.to_string(False)
         await self.send_message(
             'connection',
             peer_address=peer_address,
@@ -376,7 +376,7 @@
         if connection := self.speaker().connection:
             await self.send_message(
                 'connection',
-                peer_address=str(connection.peer_address).replace('/P', ''),
+                peer_address=connection.peer_address.to_string(False),
                 peer_name=connection.peer_name,
             )
 
diff --git a/bumble/att.py b/bumble/att.py
index 55ae8a5..db8d2ba 100644
--- a/bumble/att.py
+++ b/bumble/att.py
@@ -23,13 +23,14 @@
 # Imports
 # -----------------------------------------------------------------------------
 from __future__ import annotations
+import enum
 import functools
 import struct
 from pyee import EventEmitter
-from typing import Dict, Type, TYPE_CHECKING
+from typing import Dict, Type, List, Protocol, Union, Optional, Any, TYPE_CHECKING
 
-from bumble.core import UUID, name_or_number, get_dict_key_by_value, ProtocolError
-from bumble.hci import HCI_Object, key_with_value, HCI_Constant
+from bumble.core import UUID, name_or_number, ProtocolError
+from bumble.hci import HCI_Object, key_with_value
 from bumble.colors import color
 
 if TYPE_CHECKING:
@@ -182,6 +183,7 @@
 # pylint: enable=line-too-long
 # pylint: disable=invalid-name
 
+
 # -----------------------------------------------------------------------------
 # Exceptions
 # -----------------------------------------------------------------------------
@@ -209,7 +211,7 @@
 
     pdu_classes: Dict[int, Type[ATT_PDU]] = {}
     op_code = 0
-    name = None
+    name: str
 
     @staticmethod
     def from_bytes(pdu):
@@ -720,47 +722,67 @@
 
 
 # -----------------------------------------------------------------------------
+class ConnectionValue(Protocol):
+    def read(self, connection) -> bytes:
+        ...
+
+    def write(self, connection, value: bytes) -> None:
+        ...
+
+
+# -----------------------------------------------------------------------------
 class Attribute(EventEmitter):
-    # Permission flags
-    READABLE = 0x01
-    WRITEABLE = 0x02
-    READ_REQUIRES_ENCRYPTION = 0x04
-    WRITE_REQUIRES_ENCRYPTION = 0x08
-    READ_REQUIRES_AUTHENTICATION = 0x10
-    WRITE_REQUIRES_AUTHENTICATION = 0x20
-    READ_REQUIRES_AUTHORIZATION = 0x40
-    WRITE_REQUIRES_AUTHORIZATION = 0x80
+    class Permissions(enum.IntFlag):
+        READABLE = 0x01
+        WRITEABLE = 0x02
+        READ_REQUIRES_ENCRYPTION = 0x04
+        WRITE_REQUIRES_ENCRYPTION = 0x08
+        READ_REQUIRES_AUTHENTICATION = 0x10
+        WRITE_REQUIRES_AUTHENTICATION = 0x20
+        READ_REQUIRES_AUTHORIZATION = 0x40
+        WRITE_REQUIRES_AUTHORIZATION = 0x80
 
-    PERMISSION_NAMES = {
-        READABLE: 'READABLE',
-        WRITEABLE: 'WRITEABLE',
-        READ_REQUIRES_ENCRYPTION: 'READ_REQUIRES_ENCRYPTION',
-        WRITE_REQUIRES_ENCRYPTION: 'WRITE_REQUIRES_ENCRYPTION',
-        READ_REQUIRES_AUTHENTICATION: 'READ_REQUIRES_AUTHENTICATION',
-        WRITE_REQUIRES_AUTHENTICATION: 'WRITE_REQUIRES_AUTHENTICATION',
-        READ_REQUIRES_AUTHORIZATION: 'READ_REQUIRES_AUTHORIZATION',
-        WRITE_REQUIRES_AUTHORIZATION: 'WRITE_REQUIRES_AUTHORIZATION',
-    }
+        @classmethod
+        def from_string(cls, permissions_str: str) -> Attribute.Permissions:
+            try:
+                return functools.reduce(
+                    lambda x, y: x | Attribute.Permissions[y],
+                    permissions_str.replace('|', ',').split(","),
+                    Attribute.Permissions(0),
+                )
+            except TypeError as exc:
+                # The check for `p.name is not None` here is needed because for InFlag
+                # enums, the .name property can be None, when the enum value is 0,
+                # so the type hint for .name is Optional[str].
+                enum_list: List[str] = [p.name for p in cls if p.name is not None]
+                enum_list_str = ",".join(enum_list)
+                raise TypeError(
+                    f"Attribute::permissions error:\nExpected a string containing any of the keys, separated by commas: {enum_list_str  }\nGot: {permissions_str}"
+                ) from exc
 
-    @staticmethod
-    def string_to_permissions(permissions_str: str):
-        try:
-            return functools.reduce(
-                lambda x, y: x | get_dict_key_by_value(Attribute.PERMISSION_NAMES, y),
-                permissions_str.split(","),
-                0,
-            )
-        except TypeError as exc:
-            raise TypeError(
-                f"Attribute::permissions error:\nExpected a string containing any of the keys, separated by commas: {','.join(Attribute.PERMISSION_NAMES.values())}\nGot: {permissions_str}"
-            ) from exc
+    # Permission flags(legacy-use only)
+    READABLE = Permissions.READABLE
+    WRITEABLE = Permissions.WRITEABLE
+    READ_REQUIRES_ENCRYPTION = Permissions.READ_REQUIRES_ENCRYPTION
+    WRITE_REQUIRES_ENCRYPTION = Permissions.WRITE_REQUIRES_ENCRYPTION
+    READ_REQUIRES_AUTHENTICATION = Permissions.READ_REQUIRES_AUTHENTICATION
+    WRITE_REQUIRES_AUTHENTICATION = Permissions.WRITE_REQUIRES_AUTHENTICATION
+    READ_REQUIRES_AUTHORIZATION = Permissions.READ_REQUIRES_AUTHORIZATION
+    WRITE_REQUIRES_AUTHORIZATION = Permissions.WRITE_REQUIRES_AUTHORIZATION
 
-    def __init__(self, attribute_type, permissions, value=b''):
+    value: Union[str, bytes, ConnectionValue]
+
+    def __init__(
+        self,
+        attribute_type: Union[str, bytes, UUID],
+        permissions: Union[str, Attribute.Permissions],
+        value: Union[str, bytes, ConnectionValue] = b'',
+    ) -> None:
         EventEmitter.__init__(self)
         self.handle = 0
         self.end_group_handle = 0
         if isinstance(permissions, str):
-            self.permissions = self.string_to_permissions(permissions)
+            self.permissions = Attribute.Permissions.from_string(permissions)
         else:
             self.permissions = permissions
 
@@ -778,22 +800,26 @@
         else:
             self.value = value
 
-    def encode_value(self, value):
+    def encode_value(self, value: Any) -> bytes:
         return value
 
-    def decode_value(self, value_bytes):
+    def decode_value(self, value_bytes: bytes) -> Any:
         return value_bytes
 
-    def read_value(self, connection: Connection):
+    def read_value(self, connection: Optional[Connection]) -> bytes:
         if (
-            self.permissions & self.READ_REQUIRES_ENCRYPTION
-        ) and not connection.encryption:
+            (self.permissions & self.READ_REQUIRES_ENCRYPTION)
+            and connection is not None
+            and not connection.encryption
+        ):
             raise ATT_Error(
                 error_code=ATT_INSUFFICIENT_ENCRYPTION_ERROR, att_handle=self.handle
             )
         if (
-            self.permissions & self.READ_REQUIRES_AUTHENTICATION
-        ) and not connection.authenticated:
+            (self.permissions & self.READ_REQUIRES_AUTHENTICATION)
+            and connection is not None
+            and not connection.authenticated
+        ):
             raise ATT_Error(
                 error_code=ATT_INSUFFICIENT_AUTHENTICATION_ERROR, att_handle=self.handle
             )
@@ -803,9 +829,9 @@
                 error_code=ATT_INSUFFICIENT_AUTHORIZATION_ERROR, att_handle=self.handle
             )
 
-        if read := getattr(self.value, 'read', None):
+        if hasattr(self.value, 'read'):
             try:
-                value = read(connection)  # pylint: disable=not-callable
+                value = self.value.read(connection)
             except ATT_Error as error:
                 raise ATT_Error(
                     error_code=error.error_code, att_handle=self.handle
@@ -815,7 +841,7 @@
 
         return self.encode_value(value)
 
-    def write_value(self, connection: Connection, value_bytes):
+    def write_value(self, connection: Connection, value_bytes: bytes) -> None:
         if (
             self.permissions & self.WRITE_REQUIRES_ENCRYPTION
         ) and not connection.encryption:
@@ -836,9 +862,9 @@
 
         value = self.decode_value(value_bytes)
 
-        if write := getattr(self.value, 'write', None):
+        if hasattr(self.value, 'write'):
             try:
-                write(connection, value)  # pylint: disable=not-callable
+                self.value.write(connection, value)  # pylint: disable=not-callable
             except ATT_Error as error:
                 raise ATT_Error(
                     error_code=error.error_code, att_handle=self.handle
diff --git a/bumble/core.py b/bumble/core.py
index 4dff432..4a67d6e 100644
--- a/bumble/core.py
+++ b/bumble/core.py
@@ -80,7 +80,7 @@
 
     def __init__(
         self,
-        error_code: int | None,
+        error_code: Optional[int],
         error_namespace: str = '',
         error_name: str = '',
         details: str = '',
diff --git a/bumble/device.py b/bumble/device.py
index 9a784e7..b01dc58 100644
--- a/bumble/device.py
+++ b/bumble/device.py
@@ -1186,8 +1186,8 @@
     def create_l2cap_registrar(self, psm):
         return lambda handler: self.register_l2cap_server(psm, handler)
 
-    def register_l2cap_server(self, psm, server):
-        self.l2cap_channel_manager.register_server(psm, server)
+    def register_l2cap_server(self, psm, server) -> int:
+        return self.l2cap_channel_manager.register_server(psm, server)
 
     def register_l2cap_channel_server(
         self,
@@ -2758,7 +2758,9 @@
             self.abort_on(
                 'flush',
                 self.start_advertising(
-                    advertising_type=self.advertising_type, auto_restart=True
+                    advertising_type=self.advertising_type,
+                    own_address_type=self.advertising_own_address_type,
+                    auto_restart=True,
                 ),
             )
 
diff --git a/bumble/gatt.py b/bumble/gatt.py
index 067f31d..fe3e85c 100644
--- a/bumble/gatt.py
+++ b/bumble/gatt.py
@@ -28,7 +28,7 @@
 import functools
 import logging
 import struct
-from typing import Optional, Sequence, List
+from typing import Optional, Sequence, Iterable, List, Union
 
 from .colors import color
 from .core import UUID, get_dict_key_by_value
@@ -187,7 +187,7 @@
 # -----------------------------------------------------------------------------
 
 
-def show_services(services):
+def show_services(services: Iterable[Service]) -> None:
     for service in services:
         print(color(str(service), 'cyan'))
 
@@ -210,11 +210,11 @@
 
     def __init__(
         self,
-        uuid,
+        uuid: Union[str, UUID],
         characteristics: List[Characteristic],
         primary=True,
         included_services: List[Service] = [],
-    ):
+    ) -> None:
         # Convert the uuid to a UUID object if it isn't already
         if isinstance(uuid, str):
             uuid = UUID(uuid)
@@ -239,7 +239,7 @@
         """
         return None
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'Service(handle=0x{self.handle:04X}, '
             f'end=0x{self.end_group_handle:04X}, '
@@ -255,9 +255,11 @@
     to expose their UUID as a class property
     '''
 
-    UUID: Optional[UUID] = None
+    UUID: UUID
 
-    def __init__(self, characteristics, primary=True):
+    def __init__(
+        self, characteristics: List[Characteristic], primary: bool = True
+    ) -> None:
         super().__init__(self.UUID, characteristics, primary)
 
 
@@ -269,7 +271,7 @@
 
     service: Service
 
-    def __init__(self, service):
+    def __init__(self, service: Service) -> None:
         declaration_bytes = struct.pack(
             '<HH2s', service.handle, service.end_group_handle, service.uuid.to_bytes()
         )
@@ -278,7 +280,7 @@
         )
         self.service = service
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'IncludedServiceDefinition(handle=0x{self.handle:04X}, '
             f'group_starting_handle=0x{self.service.handle:04X}, '
@@ -326,7 +328,7 @@
                     f"Characteristic.Properties::from_string() error:\nExpected a string containing any of the keys, separated by , or |: {enum_list_str}\nGot: {properties_str}"
                 )
 
-        def __str__(self):
+        def __str__(self) -> str:
             # NOTE: we override this method to offer a consistent result between python
             # versions: the value returned by IntFlag.__str__() changed in version 11.
             return '|'.join(
@@ -348,10 +350,10 @@
 
     def __init__(
         self,
-        uuid,
+        uuid: Union[str, bytes, UUID],
         properties: Characteristic.Properties,
-        permissions,
-        value=b'',
+        permissions: Union[str, Attribute.Permissions],
+        value: Union[str, bytes, CharacteristicValue] = b'',
         descriptors: Sequence[Descriptor] = (),
     ):
         super().__init__(uuid, permissions, value)
@@ -369,7 +371,7 @@
     def has_properties(self, properties: Characteristic.Properties) -> bool:
         return self.properties & properties == properties
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'Characteristic(handle=0x{self.handle:04X}, '
             f'end=0x{self.end_group_handle:04X}, '
@@ -386,7 +388,7 @@
 
     characteristic: Characteristic
 
-    def __init__(self, characteristic, value_handle):
+    def __init__(self, characteristic: Characteristic, value_handle: int) -> None:
         declaration_bytes = (
             struct.pack('<BH', characteristic.properties, value_handle)
             + characteristic.uuid.to_pdu_bytes()
@@ -397,7 +399,7 @@
         self.value_handle = value_handle
         self.characteristic = characteristic
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'CharacteristicDeclaration(handle=0x{self.handle:04X}, '
             f'value_handle=0x{self.value_handle:04X}, '
@@ -520,7 +522,7 @@
 
         return self.wrapped_characteristic.unsubscribe(subscriber)
 
-    def __str__(self):
+    def __str__(self) -> str:
         wrapped = str(self.wrapped_characteristic)
         return f'{self.__class__.__name__}({wrapped})'
 
@@ -600,10 +602,10 @@
     Adapter that converts strings to/from bytes using UTF-8 encoding
     '''
 
-    def encode_value(self, value):
+    def encode_value(self, value: str) -> bytes:
         return value.encode('utf-8')
 
-    def decode_value(self, value):
+    def decode_value(self, value: bytes) -> str:
         return value.decode('utf-8')
 
 
@@ -613,7 +615,7 @@
     See Vol 3, Part G - 3.3.3 Characteristic Descriptor Declarations
     '''
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'Descriptor(handle=0x{self.handle:04X}, '
             f'type={self.type}, '
diff --git a/bumble/gatt_client.py b/bumble/gatt_client.py
index a33039e..e3b8bb2 100644
--- a/bumble/gatt_client.py
+++ b/bumble/gatt_client.py
@@ -28,7 +28,18 @@
 import logging
 import struct
 from datetime import datetime
-from typing import List, Optional, Dict, Tuple, Callable, Union, Any
+from typing import (
+    List,
+    Optional,
+    Dict,
+    Tuple,
+    Callable,
+    Union,
+    Any,
+    Iterable,
+    Type,
+    TYPE_CHECKING,
+)
 
 from pyee import EventEmitter
 
@@ -66,8 +77,12 @@
     GATT_INCLUDE_ATTRIBUTE_TYPE,
     Characteristic,
     ClientCharacteristicConfigurationBits,
+    TemplateService,
 )
 
+if TYPE_CHECKING:
+    from bumble.device import Connection
+
 # -----------------------------------------------------------------------------
 # Logging
 # -----------------------------------------------------------------------------
@@ -78,16 +93,16 @@
 # Proxies
 # -----------------------------------------------------------------------------
 class AttributeProxy(EventEmitter):
-    client: Client
-
-    def __init__(self, client, handle, end_group_handle, attribute_type):
+    def __init__(
+        self, client: Client, handle: int, end_group_handle: int, attribute_type: UUID
+    ) -> None:
         EventEmitter.__init__(self)
         self.client = client
         self.handle = handle
         self.end_group_handle = end_group_handle
         self.type = attribute_type
 
-    async def read_value(self, no_long_read=False):
+    async def read_value(self, no_long_read: bool = False) -> bytes:
         return self.decode_value(
             await self.client.read_value(self.handle, no_long_read)
         )
@@ -97,13 +112,13 @@
             self.handle, self.encode_value(value), with_response
         )
 
-    def encode_value(self, value):
+    def encode_value(self, value: Any) -> bytes:
         return value
 
-    def decode_value(self, value_bytes):
+    def decode_value(self, value_bytes: bytes) -> Any:
         return value_bytes
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f'Attribute(handle=0x{self.handle:04X}, type={self.type})'
 
 
@@ -136,14 +151,14 @@
     def get_characteristics_by_uuid(self, uuid):
         return self.client.get_characteristics_by_uuid(uuid, self)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f'Service(handle=0x{self.handle:04X}, uuid={self.uuid})'
 
 
 class CharacteristicProxy(AttributeProxy):
     properties: Characteristic.Properties
     descriptors: List[DescriptorProxy]
-    subscribers: Dict[Any, Callable]
+    subscribers: Dict[Any, Callable[[bytes], Any]]
 
     def __init__(
         self,
@@ -171,7 +186,9 @@
         return await self.client.discover_descriptors(self)
 
     async def subscribe(
-        self, subscriber: Optional[Callable] = None, prefer_notify=True
+        self,
+        subscriber: Optional[Callable[[bytes], Any]] = None,
+        prefer_notify: bool = True,
     ):
         if subscriber is not None:
             if subscriber in self.subscribers:
@@ -195,7 +212,7 @@
 
         return await self.client.unsubscribe(self, subscriber)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'Characteristic(handle=0x{self.handle:04X}, '
             f'uuid={self.uuid}, '
@@ -207,7 +224,7 @@
     def __init__(self, client, handle, descriptor_type):
         super().__init__(client, handle, 0, descriptor_type)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f'Descriptor(handle=0x{self.handle:04X}, type={self.type})'
 
 
@@ -216,8 +233,10 @@
     Base class for profile-specific service proxies
     '''
 
+    SERVICE_CLASS: Type[TemplateService]
+
     @classmethod
-    def from_client(cls, client):
+    def from_client(cls, client: Client) -> ProfileServiceProxy:
         return ServiceProxy.from_client(cls, client, cls.SERVICE_CLASS.UUID)
 
 
@@ -227,8 +246,12 @@
 class Client:
     services: List[ServiceProxy]
     cached_values: Dict[int, Tuple[datetime, bytes]]
+    notification_subscribers: Dict[int, Callable[[bytes], Any]]
+    indication_subscribers: Dict[int, Callable[[bytes], Any]]
+    pending_response: Optional[asyncio.futures.Future[ATT_PDU]]
+    pending_request: Optional[ATT_PDU]
 
-    def __init__(self, connection):
+    def __init__(self, connection: Connection) -> None:
         self.connection = connection
         self.mtu_exchange_done = False
         self.request_semaphore = asyncio.Semaphore(1)
@@ -241,16 +264,16 @@
         self.services = []
         self.cached_values = {}
 
-    def send_gatt_pdu(self, pdu):
+    def send_gatt_pdu(self, pdu: bytes) -> None:
         self.connection.send_l2cap_pdu(ATT_CID, pdu)
 
-    async def send_command(self, command):
+    async def send_command(self, command: ATT_PDU) -> None:
         logger.debug(
             f'GATT Command from client: [0x{self.connection.handle:04X}] {command}'
         )
         self.send_gatt_pdu(command.to_bytes())
 
-    async def send_request(self, request):
+    async def send_request(self, request: ATT_PDU):
         logger.debug(
             f'GATT Request from client: [0x{self.connection.handle:04X}] {request}'
         )
@@ -279,14 +302,14 @@
 
         return response
 
-    def send_confirmation(self, confirmation):
+    def send_confirmation(self, confirmation: ATT_Handle_Value_Confirmation) -> None:
         logger.debug(
             f'GATT Confirmation from client: [0x{self.connection.handle:04X}] '
             f'{confirmation}'
         )
         self.send_gatt_pdu(confirmation.to_bytes())
 
-    async def request_mtu(self, mtu):
+    async def request_mtu(self, mtu: int) -> int:
         # Check the range
         if mtu < ATT_DEFAULT_MTU:
             raise ValueError(f'MTU must be >= {ATT_DEFAULT_MTU}')
@@ -313,10 +336,12 @@
 
         return self.connection.att_mtu
 
-    def get_services_by_uuid(self, uuid):
+    def get_services_by_uuid(self, uuid: UUID) -> List[ServiceProxy]:
         return [service for service in self.services if service.uuid == uuid]
 
-    def get_characteristics_by_uuid(self, uuid, service=None):
+    def get_characteristics_by_uuid(
+        self, uuid: UUID, service: Optional[ServiceProxy] = None
+    ) -> List[CharacteristicProxy]:
         services = [service] if service else self.services
         return [
             c
@@ -363,7 +388,7 @@
         if not already_known:
             self.services.append(service)
 
-    async def discover_services(self, uuids=None) -> List[ServiceProxy]:
+    async def discover_services(self, uuids: Iterable[UUID] = []) -> List[ServiceProxy]:
         '''
         See Vol 3, Part G - 4.4.1 Discover All Primary Services
         '''
@@ -435,7 +460,7 @@
 
         return services
 
-    async def discover_service(self, uuid):
+    async def discover_service(self, uuid: Union[str, UUID]) -> List[ServiceProxy]:
         '''
         See Vol 3, Part G - 4.4.2 Discover Primary Service by Service UUID
         '''
@@ -468,7 +493,7 @@
                         f'{HCI_Constant.error_name(response.error_code)}'
                     )
                     # TODO raise appropriate exception
-                    return
+                    return []
                 break
 
             for attribute_handle, end_group_handle in response.handles_information:
@@ -480,7 +505,7 @@
                     logger.warning(
                         f'bogus handle values: {attribute_handle} {end_group_handle}'
                     )
-                    return
+                    return []
 
                 # Create a service proxy for this service
                 service = ServiceProxy(
@@ -721,7 +746,7 @@
 
         return descriptors
 
-    async def discover_attributes(self):
+    async def discover_attributes(self) -> List[AttributeProxy]:
         '''
         Discover all attributes, regardless of type
         '''
@@ -844,7 +869,9 @@
             # No more subscribers left
             await self.write_value(cccd, b'\x00\x00', with_response=True)
 
-    async def read_value(self, attribute, no_long_read=False):
+    async def read_value(
+        self, attribute: Union[int, AttributeProxy], no_long_read: bool = False
+    ) -> Any:
         '''
         See Vol 3, Part G - 4.8.1 Read Characteristic Value
 
@@ -905,7 +932,9 @@
         # Return the value as bytes
         return attribute_value
 
-    async def read_characteristics_by_uuid(self, uuid, service):
+    async def read_characteristics_by_uuid(
+        self, uuid: UUID, service: Optional[ServiceProxy]
+    ) -> List[bytes]:
         '''
         See Vol 3, Part G - 4.8.2 Read Using Characteristic UUID
         '''
@@ -960,7 +989,12 @@
 
         return characteristics_values
 
-    async def write_value(self, attribute, value, with_response=False):
+    async def write_value(
+        self,
+        attribute: Union[int, AttributeProxy],
+        value: bytes,
+        with_response: bool = False,
+    ) -> None:
         '''
         See Vol 3, Part G - 4.9.1 Write Without Response & 4.9.3 Write Characteristic
         Value
@@ -990,7 +1024,7 @@
                 )
             )
 
-    def on_gatt_pdu(self, att_pdu):
+    def on_gatt_pdu(self, att_pdu: ATT_PDU) -> None:
         logger.debug(
             f'GATT Response to client: [0x{self.connection.handle:04X}] {att_pdu}'
         )
@@ -1013,6 +1047,7 @@
                     return
 
             # Return the response to the coroutine that is waiting for it
+            assert self.pending_response is not None
             self.pending_response.set_result(att_pdu)
         else:
             handler_name = f'on_{att_pdu.name.lower()}'
@@ -1060,7 +1095,7 @@
         # Confirm that we received the indication
         self.send_confirmation(ATT_Handle_Value_Confirmation())
 
-    def cache_value(self, attribute_handle: int, value: bytes):
+    def cache_value(self, attribute_handle: int, value: bytes) -> None:
         self.cached_values[attribute_handle] = (
             datetime.now(),
             value,
diff --git a/bumble/gatt_server.py b/bumble/gatt_server.py
index 3624905..cdf1b5e 100644
--- a/bumble/gatt_server.py
+++ b/bumble/gatt_server.py
@@ -23,11 +23,12 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+from __future__ import annotations
 import asyncio
 import logging
 from collections import defaultdict
 import struct
-from typing import List, Tuple, Optional, TypeVar, Type
+from typing import List, Tuple, Optional, TypeVar, Type, Dict, Iterable, TYPE_CHECKING
 from pyee import EventEmitter
 
 from .colors import color
@@ -42,6 +43,7 @@
     ATT_INVALID_OFFSET_ERROR,
     ATT_REQUEST_NOT_SUPPORTED_ERROR,
     ATT_REQUESTS,
+    ATT_PDU,
     ATT_UNLIKELY_ERROR_ERROR,
     ATT_UNSUPPORTED_GROUP_TYPE_ERROR,
     ATT_Error,
@@ -73,6 +75,8 @@
     Service,
 )
 
+if TYPE_CHECKING:
+    from bumble.device import Device, Connection
 
 # -----------------------------------------------------------------------------
 # Logging
@@ -91,8 +95,13 @@
 # -----------------------------------------------------------------------------
 class Server(EventEmitter):
     attributes: List[Attribute]
+    services: List[Service]
+    attributes_by_handle: Dict[int, Attribute]
+    subscribers: Dict[int, Dict[int, bytes]]
+    indication_semaphores: defaultdict[int, asyncio.Semaphore]
+    pending_confirmations: defaultdict[int, Optional[asyncio.futures.Future]]
 
-    def __init__(self, device):
+    def __init__(self, device: Device) -> None:
         super().__init__()
         self.device = device
         self.services = []
@@ -107,16 +116,16 @@
         self.indication_semaphores = defaultdict(lambda: asyncio.Semaphore(1))
         self.pending_confirmations = defaultdict(lambda: None)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return "\n".join(map(str, self.attributes))
 
-    def send_gatt_pdu(self, connection_handle, pdu):
+    def send_gatt_pdu(self, connection_handle: int, pdu: bytes) -> None:
         self.device.send_l2cap_pdu(connection_handle, ATT_CID, pdu)
 
-    def next_handle(self):
+    def next_handle(self) -> int:
         return 1 + len(self.attributes)
 
-    def get_advertising_service_data(self):
+    def get_advertising_service_data(self) -> Dict[Attribute, bytes]:
         return {
             attribute: data
             for attribute in self.attributes
@@ -124,7 +133,7 @@
             and (data := attribute.get_advertising_data())
         }
 
-    def get_attribute(self, handle):
+    def get_attribute(self, handle: int) -> Optional[Attribute]:
         attribute = self.attributes_by_handle.get(handle)
         if attribute:
             return attribute
@@ -173,12 +182,17 @@
 
         return next(
             (
-                (attribute, self.get_attribute(attribute.characteristic.handle))
+                (
+                    attribute,
+                    self.get_attribute(attribute.characteristic.handle),
+                )  # type: ignore
                 for attribute in map(
                     self.get_attribute,
                     range(service_handle.handle, service_handle.end_group_handle + 1),
                 )
-                if attribute.type == GATT_CHARACTERISTIC_ATTRIBUTE_TYPE
+                if attribute is not None
+                and attribute.type == GATT_CHARACTERISTIC_ATTRIBUTE_TYPE
+                and isinstance(attribute, CharacteristicDeclaration)
                 and attribute.characteristic.uuid == characteristic_uuid
             ),
             None,
@@ -197,7 +211,7 @@
 
         return next(
             (
-                attribute
+                attribute  # type: ignore
                 for attribute in map(
                     self.get_attribute,
                     range(
@@ -205,12 +219,12 @@
                         characteristic_value.end_group_handle + 1,
                     ),
                 )
-                if attribute.type == descriptor_uuid
+                if attribute is not None and attribute.type == descriptor_uuid
             ),
             None,
         )
 
-    def add_attribute(self, attribute):
+    def add_attribute(self, attribute: Attribute) -> None:
         # Assign a handle to this attribute
         attribute.handle = self.next_handle()
         attribute.end_group_handle = (
@@ -220,7 +234,7 @@
         # Add this attribute to the list
         self.attributes.append(attribute)
 
-    def add_service(self, service: Service):
+    def add_service(self, service: Service) -> None:
         # Add the service attribute to the DB
         self.add_attribute(service)
 
@@ -285,11 +299,13 @@
         service.end_group_handle = self.attributes[-1].handle
         self.services.append(service)
 
-    def add_services(self, services):
+    def add_services(self, services: Iterable[Service]) -> None:
         for service in services:
             self.add_service(service)
 
-    def read_cccd(self, connection, characteristic):
+    def read_cccd(
+        self, connection: Optional[Connection], characteristic: Characteristic
+    ) -> bytes:
         if connection is None:
             return bytes([0, 0])
 
@@ -300,7 +316,12 @@
 
         return cccd or bytes([0, 0])
 
-    def write_cccd(self, connection, characteristic, value):
+    def write_cccd(
+        self,
+        connection: Connection,
+        characteristic: Characteristic,
+        value: bytes,
+    ) -> None:
         logger.debug(
             f'Subscription update for connection=0x{connection.handle:04X}, '
             f'handle=0x{characteristic.handle:04X}: {value.hex()}'
@@ -327,13 +348,19 @@
             indicate_enabled,
         )
 
-    def send_response(self, connection, response):
+    def send_response(self, connection: Connection, response: ATT_PDU) -> None:
         logger.debug(
             f'GATT Response from server: [0x{connection.handle:04X}] {response}'
         )
         self.send_gatt_pdu(connection.handle, response.to_bytes())
 
-    async def notify_subscriber(self, connection, attribute, value=None, force=False):
+    async def notify_subscriber(
+        self,
+        connection: Connection,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ) -> None:
         # Check if there's a subscriber
         if not force:
             subscribers = self.subscribers.get(connection.handle)
@@ -370,7 +397,13 @@
         )
         self.send_gatt_pdu(connection.handle, bytes(notification))
 
-    async def indicate_subscriber(self, connection, attribute, value=None, force=False):
+    async def indicate_subscriber(
+        self,
+        connection: Connection,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ) -> None:
         # Check if there's a subscriber
         if not force:
             subscribers = self.subscribers.get(connection.handle)
@@ -411,15 +444,13 @@
             assert self.pending_confirmations[connection.handle] is None
 
             # Create a future value to hold the eventual response
-            self.pending_confirmations[
+            pending_confirmation = self.pending_confirmations[
                 connection.handle
             ] = asyncio.get_running_loop().create_future()
 
             try:
                 self.send_gatt_pdu(connection.handle, indication.to_bytes())
-                await asyncio.wait_for(
-                    self.pending_confirmations[connection.handle], GATT_REQUEST_TIMEOUT
-                )
+                await asyncio.wait_for(pending_confirmation, GATT_REQUEST_TIMEOUT)
             except asyncio.TimeoutError as error:
                 logger.warning(color('!!! GATT Indicate timeout', 'red'))
                 raise TimeoutError(f'GATT timeout for {indication.name}') from error
@@ -427,8 +458,12 @@
                 self.pending_confirmations[connection.handle] = None
 
     async def notify_or_indicate_subscribers(
-        self, indicate, attribute, value=None, force=False
-    ):
+        self,
+        indicate: bool,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ) -> None:
         # Get all the connections for which there's at least one subscription
         connections = [
             connection
@@ -450,13 +485,23 @@
                 ]
             )
 
-    async def notify_subscribers(self, attribute, value=None, force=False):
+    async def notify_subscribers(
+        self,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ):
         return await self.notify_or_indicate_subscribers(False, attribute, value, force)
 
-    async def indicate_subscribers(self, attribute, value=None, force=False):
+    async def indicate_subscribers(
+        self,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ):
         return await self.notify_or_indicate_subscribers(True, attribute, value, force)
 
-    def on_disconnection(self, connection):
+    def on_disconnection(self, connection: Connection) -> None:
         if connection.handle in self.subscribers:
             del self.subscribers[connection.handle]
         if connection.handle in self.indication_semaphores:
@@ -464,7 +509,7 @@
         if connection.handle in self.pending_confirmations:
             del self.pending_confirmations[connection.handle]
 
-    def on_gatt_pdu(self, connection, att_pdu):
+    def on_gatt_pdu(self, connection: Connection, att_pdu: ATT_PDU) -> None:
         logger.debug(f'GATT Request to server: [0x{connection.handle:04X}] {att_pdu}')
         handler_name = f'on_{att_pdu.name.lower()}'
         handler = getattr(self, handler_name, None)
@@ -506,7 +551,7 @@
     #######################################################
     # ATT handlers
     #######################################################
-    def on_att_request(self, connection, pdu):
+    def on_att_request(self, connection: Connection, pdu: ATT_PDU) -> None:
         '''
         Handler for requests without a more specific handler
         '''
@@ -679,7 +724,6 @@
             and attribute.handle <= request.ending_handle
             and pdu_space_available
         ):
-
             try:
                 attribute_value = attribute.read_value(connection)
             except ATT_Error as error:
diff --git a/bumble/hci.py b/bumble/hci.py
index b7014dd..41deed2 100644
--- a/bumble/hci.py
+++ b/bumble/hci.py
@@ -4397,7 +4397,7 @@
         if len(parameters) != length:
             raise ValueError('invalid packet length')
 
-        cls: Type[HCI_Event | HCI_LE_Meta_Event] | None
+        cls: Any
         if event_code == HCI_LE_META_EVENT:
             # We do this dispatch here and not in the subclass in order to avoid call
             # loops
diff --git a/bumble/l2cap.py b/bumble/l2cap.py
index fea8a1d..cccb172 100644
--- a/bumble/l2cap.py
+++ b/bumble/l2cap.py
@@ -17,6 +17,7 @@
 # -----------------------------------------------------------------------------
 from __future__ import annotations
 import asyncio
+import enum
 import logging
 import struct
 
@@ -676,56 +677,35 @@
 
 # -----------------------------------------------------------------------------
 class Channel(EventEmitter):
-    # States
-    CLOSED = 0x00
-    WAIT_CONNECT = 0x01
-    WAIT_CONNECT_RSP = 0x02
-    OPEN = 0x03
-    WAIT_DISCONNECT = 0x04
-    WAIT_CREATE = 0x05
-    WAIT_CREATE_RSP = 0x06
-    WAIT_MOVE = 0x07
-    WAIT_MOVE_RSP = 0x08
-    WAIT_MOVE_CONFIRM = 0x09
-    WAIT_CONFIRM_RSP = 0x0A
+    class State(enum.IntEnum):
+        # States
+        CLOSED = 0x00
+        WAIT_CONNECT = 0x01
+        WAIT_CONNECT_RSP = 0x02
+        OPEN = 0x03
+        WAIT_DISCONNECT = 0x04
+        WAIT_CREATE = 0x05
+        WAIT_CREATE_RSP = 0x06
+        WAIT_MOVE = 0x07
+        WAIT_MOVE_RSP = 0x08
+        WAIT_MOVE_CONFIRM = 0x09
+        WAIT_CONFIRM_RSP = 0x0A
 
-    # CONFIG substates
-    WAIT_CONFIG = 0x10
-    WAIT_SEND_CONFIG = 0x11
-    WAIT_CONFIG_REQ_RSP = 0x12
-    WAIT_CONFIG_RSP = 0x13
-    WAIT_CONFIG_REQ = 0x14
-    WAIT_IND_FINAL_RSP = 0x15
-    WAIT_FINAL_RSP = 0x16
-    WAIT_CONTROL_IND = 0x17
-
-    STATE_NAMES = {
-        CLOSED: 'CLOSED',
-        WAIT_CONNECT: 'WAIT_CONNECT',
-        WAIT_CONNECT_RSP: 'WAIT_CONNECT_RSP',
-        OPEN: 'OPEN',
-        WAIT_DISCONNECT: 'WAIT_DISCONNECT',
-        WAIT_CREATE: 'WAIT_CREATE',
-        WAIT_CREATE_RSP: 'WAIT_CREATE_RSP',
-        WAIT_MOVE: 'WAIT_MOVE',
-        WAIT_MOVE_RSP: 'WAIT_MOVE_RSP',
-        WAIT_MOVE_CONFIRM: 'WAIT_MOVE_CONFIRM',
-        WAIT_CONFIRM_RSP: 'WAIT_CONFIRM_RSP',
-        WAIT_CONFIG: 'WAIT_CONFIG',
-        WAIT_SEND_CONFIG: 'WAIT_SEND_CONFIG',
-        WAIT_CONFIG_REQ_RSP: 'WAIT_CONFIG_REQ_RSP',
-        WAIT_CONFIG_RSP: 'WAIT_CONFIG_RSP',
-        WAIT_CONFIG_REQ: 'WAIT_CONFIG_REQ',
-        WAIT_IND_FINAL_RSP: 'WAIT_IND_FINAL_RSP',
-        WAIT_FINAL_RSP: 'WAIT_FINAL_RSP',
-        WAIT_CONTROL_IND: 'WAIT_CONTROL_IND',
-    }
+        # CONFIG substates
+        WAIT_CONFIG = 0x10
+        WAIT_SEND_CONFIG = 0x11
+        WAIT_CONFIG_REQ_RSP = 0x12
+        WAIT_CONFIG_RSP = 0x13
+        WAIT_CONFIG_REQ = 0x14
+        WAIT_IND_FINAL_RSP = 0x15
+        WAIT_FINAL_RSP = 0x16
+        WAIT_CONTROL_IND = 0x17
 
     connection_result: Optional[asyncio.Future[None]]
     disconnection_result: Optional[asyncio.Future[None]]
     response: Optional[asyncio.Future[bytes]]
     sink: Optional[Callable[[bytes], Any]]
-    state: int
+    state: State
     connection: Connection
 
     def __init__(
@@ -741,7 +721,7 @@
         self.manager = manager
         self.connection = connection
         self.signaling_cid = signaling_cid
-        self.state = Channel.CLOSED
+        self.state = self.State.CLOSED
         self.mtu = mtu
         self.psm = psm
         self.source_cid = source_cid
@@ -751,13 +731,11 @@
         self.disconnection_result = None
         self.sink = None
 
-    def change_state(self, new_state: int) -> None:
-        logger.debug(
-            f'{self} state change -> {color(Channel.STATE_NAMES[new_state], "cyan")}'
-        )
+    def _change_state(self, new_state: State) -> None:
+        logger.debug(f'{self} state change -> {color(new_state.name, "cyan")}')
         self.state = new_state
 
-    def send_pdu(self, pdu: SupportsBytes | bytes) -> None:
+    def send_pdu(self, pdu: Union[SupportsBytes, bytes]) -> None:
         self.manager.send_pdu(self.connection, self.destination_cid, pdu)
 
     def send_control_frame(self, frame: L2CAP_Control_Frame) -> None:
@@ -767,7 +745,7 @@
         # Check that there isn't already a request pending
         if self.response:
             raise InvalidStateError('request already pending')
-        if self.state != Channel.OPEN:
+        if self.state != self.State.OPEN:
             raise InvalidStateError('channel not open')
 
         self.response = asyncio.get_running_loop().create_future()
@@ -787,14 +765,14 @@
             )
 
     async def connect(self) -> None:
-        if self.state != Channel.CLOSED:
+        if self.state != self.State.CLOSED:
             raise InvalidStateError('invalid state')
 
         # Check that we can start a new connection
         if self.connection_result:
             raise RuntimeError('connection already pending')
 
-        self.change_state(Channel.WAIT_CONNECT_RSP)
+        self._change_state(self.State.WAIT_CONNECT_RSP)
         self.send_control_frame(
             L2CAP_Connection_Request(
                 identifier=self.manager.next_identifier(self.connection),
@@ -814,10 +792,10 @@
             self.connection_result = None
 
     async def disconnect(self) -> None:
-        if self.state != Channel.OPEN:
+        if self.state != self.State.OPEN:
             raise InvalidStateError('invalid state')
 
-        self.change_state(Channel.WAIT_DISCONNECT)
+        self._change_state(self.State.WAIT_DISCONNECT)
         self.send_control_frame(
             L2CAP_Disconnection_Request(
                 identifier=self.manager.next_identifier(self.connection),
@@ -832,8 +810,8 @@
         return await self.disconnection_result
 
     def abort(self) -> None:
-        if self.state == self.OPEN:
-            self.change_state(self.CLOSED)
+        if self.state == self.State.OPEN:
+            self._change_state(self.State.CLOSED)
             self.emit('close')
 
     def send_configure_request(self) -> None:
@@ -856,7 +834,7 @@
 
     def on_connection_request(self, request) -> None:
         self.destination_cid = request.source_cid
-        self.change_state(Channel.WAIT_CONNECT)
+        self._change_state(self.State.WAIT_CONNECT)
         self.send_control_frame(
             L2CAP_Connection_Response(
                 identifier=request.identifier,
@@ -866,24 +844,24 @@
                 status=0x0000,
             )
         )
-        self.change_state(Channel.WAIT_CONFIG)
+        self._change_state(self.State.WAIT_CONFIG)
         self.send_configure_request()
-        self.change_state(Channel.WAIT_CONFIG_REQ_RSP)
+        self._change_state(self.State.WAIT_CONFIG_REQ_RSP)
 
     def on_connection_response(self, response):
-        if self.state != Channel.WAIT_CONNECT_RSP:
+        if self.state != self.State.WAIT_CONNECT_RSP:
             logger.warning(color('invalid state', 'red'))
             return
 
         if response.result == L2CAP_Connection_Response.CONNECTION_SUCCESSFUL:
             self.destination_cid = response.destination_cid
-            self.change_state(Channel.WAIT_CONFIG)
+            self._change_state(self.State.WAIT_CONFIG)
             self.send_configure_request()
-            self.change_state(Channel.WAIT_CONFIG_REQ_RSP)
+            self._change_state(self.State.WAIT_CONFIG_REQ_RSP)
         elif response.result == L2CAP_Connection_Response.CONNECTION_PENDING:
             pass
         else:
-            self.change_state(Channel.CLOSED)
+            self._change_state(self.State.CLOSED)
             self.connection_result.set_exception(
                 ProtocolError(
                     response.result,
@@ -895,9 +873,9 @@
 
     def on_configure_request(self, request) -> None:
         if self.state not in (
-            Channel.WAIT_CONFIG,
-            Channel.WAIT_CONFIG_REQ,
-            Channel.WAIT_CONFIG_REQ_RSP,
+            self.State.WAIT_CONFIG,
+            self.State.WAIT_CONFIG_REQ,
+            self.State.WAIT_CONFIG_REQ_RSP,
         ):
             logger.warning(color('invalid state', 'red'))
             return
@@ -918,25 +896,28 @@
                 options=request.options,  # TODO: don't accept everything blindly
             )
         )
-        if self.state == Channel.WAIT_CONFIG:
-            self.change_state(Channel.WAIT_SEND_CONFIG)
+        if self.state == self.State.WAIT_CONFIG:
+            self._change_state(self.State.WAIT_SEND_CONFIG)
             self.send_configure_request()
-            self.change_state(Channel.WAIT_CONFIG_RSP)
-        elif self.state == Channel.WAIT_CONFIG_REQ:
-            self.change_state(Channel.OPEN)
+            self._change_state(self.State.WAIT_CONFIG_RSP)
+        elif self.state == self.State.WAIT_CONFIG_REQ:
+            self._change_state(self.State.OPEN)
             if self.connection_result:
                 self.connection_result.set_result(None)
                 self.connection_result = None
             self.emit('open')
-        elif self.state == Channel.WAIT_CONFIG_REQ_RSP:
-            self.change_state(Channel.WAIT_CONFIG_RSP)
+        elif self.state == self.State.WAIT_CONFIG_REQ_RSP:
+            self._change_state(self.State.WAIT_CONFIG_RSP)
 
     def on_configure_response(self, response) -> None:
         if response.result == L2CAP_Configure_Response.SUCCESS:
-            if self.state == Channel.WAIT_CONFIG_REQ_RSP:
-                self.change_state(Channel.WAIT_CONFIG_REQ)
-            elif self.state in (Channel.WAIT_CONFIG_RSP, Channel.WAIT_CONTROL_IND):
-                self.change_state(Channel.OPEN)
+            if self.state == self.State.WAIT_CONFIG_REQ_RSP:
+                self._change_state(self.State.WAIT_CONFIG_REQ)
+            elif self.state in (
+                self.State.WAIT_CONFIG_RSP,
+                self.State.WAIT_CONTROL_IND,
+            ):
+                self._change_state(self.State.OPEN)
                 if self.connection_result:
                     self.connection_result.set_result(None)
                     self.connection_result = None
@@ -966,7 +947,7 @@
             # TODO: decide how to fail gracefully
 
     def on_disconnection_request(self, request) -> None:
-        if self.state in (Channel.OPEN, Channel.WAIT_DISCONNECT):
+        if self.state in (self.State.OPEN, self.State.WAIT_DISCONNECT):
             self.send_control_frame(
                 L2CAP_Disconnection_Response(
                     identifier=request.identifier,
@@ -974,14 +955,14 @@
                     source_cid=request.source_cid,
                 )
             )
-            self.change_state(Channel.CLOSED)
+            self._change_state(self.State.CLOSED)
             self.emit('close')
             self.manager.on_channel_closed(self)
         else:
             logger.warning(color('invalid state', 'red'))
 
     def on_disconnection_response(self, response) -> None:
-        if self.state != Channel.WAIT_DISCONNECT:
+        if self.state != self.State.WAIT_DISCONNECT:
             logger.warning(color('invalid state', 'red'))
             return
 
@@ -992,7 +973,7 @@
             logger.warning('unexpected source or destination CID')
             return
 
-        self.change_state(Channel.CLOSED)
+        self._change_state(self.State.CLOSED)
         if self.disconnection_result:
             self.disconnection_result.set_result(None)
             self.disconnection_result = None
@@ -1004,7 +985,7 @@
             f'Channel({self.source_cid}->{self.destination_cid}, '
             f'PSM={self.psm}, '
             f'MTU={self.mtu}, '
-            f'state={Channel.STATE_NAMES[self.state]})'
+            f'state={self.state.name})'
         )
 
 
@@ -1014,33 +995,21 @@
     LE Credit-based Connection Oriented Channel
     """
 
-    INIT = 0
-    CONNECTED = 1
-    CONNECTING = 2
-    DISCONNECTING = 3
-    DISCONNECTED = 4
-    CONNECTION_ERROR = 5
-
-    STATE_NAMES = {
-        INIT: 'INIT',
-        CONNECTED: 'CONNECTED',
-        CONNECTING: 'CONNECTING',
-        DISCONNECTING: 'DISCONNECTING',
-        DISCONNECTED: 'DISCONNECTED',
-        CONNECTION_ERROR: 'CONNECTION_ERROR',
-    }
+    class State(enum.IntEnum):
+        INIT = 0
+        CONNECTED = 1
+        CONNECTING = 2
+        DISCONNECTING = 3
+        DISCONNECTED = 4
+        CONNECTION_ERROR = 5
 
     out_queue: Deque[bytes]
     connection_result: Optional[asyncio.Future[LeConnectionOrientedChannel]]
     disconnection_result: Optional[asyncio.Future[None]]
     out_sdu: Optional[bytes]
-    state: int
+    state: State
     connection: Connection
 
-    @staticmethod
-    def state_name(state: int) -> str:
-        return name_or_number(LeConnectionOrientedChannel.STATE_NAMES, state)
-
     def __init__(
         self,
         manager: ChannelManager,
@@ -1083,22 +1052,20 @@
         self.drained.set()
 
         if connected:
-            self.state = LeConnectionOrientedChannel.CONNECTED
+            self.state = self.State.CONNECTED
         else:
-            self.state = LeConnectionOrientedChannel.INIT
+            self.state = self.State.INIT
 
-    def change_state(self, new_state: int) -> None:
-        logger.debug(
-            f'{self} state change -> {color(self.state_name(new_state), "cyan")}'
-        )
+    def _change_state(self, new_state: State) -> None:
+        logger.debug(f'{self} state change -> {color(new_state.name, "cyan")}')
         self.state = new_state
 
-        if new_state == self.CONNECTED:
+        if new_state == self.State.CONNECTED:
             self.emit('open')
-        elif new_state == self.DISCONNECTED:
+        elif new_state == self.State.DISCONNECTED:
             self.emit('close')
 
-    def send_pdu(self, pdu: SupportsBytes | bytes) -> None:
+    def send_pdu(self, pdu: Union[SupportsBytes, bytes]) -> None:
         self.manager.send_pdu(self.connection, self.destination_cid, pdu)
 
     def send_control_frame(self, frame: L2CAP_Control_Frame) -> None:
@@ -1106,7 +1073,7 @@
 
     async def connect(self) -> LeConnectionOrientedChannel:
         # Check that we're in the right state
-        if self.state != self.INIT:
+        if self.state != self.State.INIT:
             raise InvalidStateError('not in a connectable state')
 
         # Check that we can start a new connection
@@ -1114,7 +1081,7 @@
         if identifier in self.manager.le_coc_requests:
             raise RuntimeError('too many concurrent connection requests')
 
-        self.change_state(self.CONNECTING)
+        self._change_state(self.State.CONNECTING)
         request = L2CAP_LE_Credit_Based_Connection_Request(
             identifier=identifier,
             le_psm=self.le_psm,
@@ -1134,10 +1101,10 @@
 
     async def disconnect(self) -> None:
         # Check that we're connected
-        if self.state != self.CONNECTED:
+        if self.state != self.State.CONNECTED:
             raise InvalidStateError('not connected')
 
-        self.change_state(self.DISCONNECTING)
+        self._change_state(self.State.DISCONNECTING)
         self.flush_output()
         self.send_control_frame(
             L2CAP_Disconnection_Request(
@@ -1153,15 +1120,15 @@
         return await self.disconnection_result
 
     def abort(self) -> None:
-        if self.state == self.CONNECTED:
-            self.change_state(self.DISCONNECTED)
+        if self.state == self.State.CONNECTED:
+            self._change_state(self.State.DISCONNECTED)
 
     def on_pdu(self, pdu: bytes) -> None:
         if self.sink is None:
             logger.warning('received pdu without a sink')
             return
 
-        if self.state != self.CONNECTED:
+        if self.state != self.State.CONNECTED:
             logger.warning('received PDU while not connected, dropping')
 
         # Manage the peer credits
@@ -1240,7 +1207,7 @@
             self.credits = response.initial_credits
             self.connected = True
             self.connection_result.set_result(self)
-            self.change_state(self.CONNECTED)
+            self._change_state(self.State.CONNECTED)
         else:
             self.connection_result.set_exception(
                 ProtocolError(
@@ -1251,7 +1218,7 @@
                     ),
                 )
             )
-            self.change_state(self.CONNECTION_ERROR)
+            self._change_state(self.State.CONNECTION_ERROR)
 
         # Cleanup
         self.connection_result = None
@@ -1271,11 +1238,11 @@
                 source_cid=request.source_cid,
             )
         )
-        self.change_state(self.DISCONNECTED)
+        self._change_state(self.State.DISCONNECTED)
         self.flush_output()
 
     def on_disconnection_response(self, response) -> None:
-        if self.state != self.DISCONNECTING:
+        if self.state != self.State.DISCONNECTING:
             logger.warning(color('invalid state', 'red'))
             return
 
@@ -1286,7 +1253,7 @@
             logger.warning('unexpected source or destination CID')
             return
 
-        self.change_state(self.DISCONNECTED)
+        self._change_state(self.State.DISCONNECTED)
         if self.disconnection_result:
             self.disconnection_result.set_result(None)
             self.disconnection_result = None
@@ -1339,7 +1306,7 @@
                 return
 
     def write(self, data: bytes) -> None:
-        if self.state != self.CONNECTED:
+        if self.state != self.State.CONNECTED:
             logger.warning('not connected, dropping data')
             return
 
@@ -1367,7 +1334,7 @@
     def __str__(self) -> str:
         return (
             f'CoC({self.source_cid}->{self.destination_cid}, '
-            f'State={self.state_name(self.state)}, '
+            f'State={self.state.name}, '
             f'PSM={self.le_psm}, '
             f'MTU={self.mtu}/{self.peer_mtu}, '
             f'MPS={self.mps}/{self.peer_mps}, '
@@ -1571,7 +1538,7 @@
         if connection_handle in self.identifiers:
             del self.identifiers[connection_handle]
 
-    def send_pdu(self, connection, cid: int, pdu: SupportsBytes | bytes) -> None:
+    def send_pdu(self, connection, cid: int, pdu: Union[SupportsBytes, bytes]) -> None:
         pdu_str = pdu.hex() if isinstance(pdu, bytes) else str(pdu)
         logger.debug(
             f'{color(">>> Sending L2CAP PDU", "blue")} '
diff --git a/bumble/pandora/security.py b/bumble/pandora/security.py
index 96fce85..0f31512 100644
--- a/bumble/pandora/security.py
+++ b/bumble/pandora/security.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import asyncio
+import contextlib
 import grpc
 import logging
 
@@ -27,8 +28,8 @@
 )
 from bumble.device import Connection as BumbleConnection, Device
 from bumble.hci import HCI_Error
+from bumble.utils import EventWatcher
 from bumble.pairing import PairingConfig, PairingDelegate as BasePairingDelegate
-from contextlib import suppress
 from google.protobuf import any_pb2  # pytype: disable=pyi-error
 from google.protobuf import empty_pb2  # pytype: disable=pyi-error
 from google.protobuf import wrappers_pb2  # pytype: disable=pyi-error
@@ -232,7 +233,11 @@
                 sc=config.pairing_sc_enable,
                 mitm=config.pairing_mitm_enable,
                 bonding=config.pairing_bonding_enable,
-                identity_address_type=config.identity_address_type,
+                identity_address_type=(
+                    PairingConfig.AddressType.PUBLIC
+                    if connection.self_address.is_public
+                    else config.identity_address_type
+                ),
                 delegate=PairingDelegate(
                     connection,
                     self,
@@ -294,23 +299,35 @@
             try:
                 self.log.debug('Pair...')
 
-                if (
-                    connection.transport == BT_LE_TRANSPORT
-                    and connection.role == BT_PERIPHERAL_ROLE
-                ):
-                    wait_for_security: asyncio.Future[
-                        bool
-                    ] = asyncio.get_running_loop().create_future()
-                    connection.on("pairing", lambda *_: wait_for_security.set_result(True))  # type: ignore
-                    connection.on("pairing_failure", wait_for_security.set_exception)
+                security_result = asyncio.get_running_loop().create_future()
 
-                    connection.request_pairing()
+                with contextlib.closing(EventWatcher()) as watcher:
 
-                    await wait_for_security
-                else:
-                    await connection.pair()
+                    @watcher.on(connection, 'pairing')
+                    def on_pairing(*_: Any) -> None:
+                        security_result.set_result('success')
 
-                self.log.debug('Paired')
+                    @watcher.on(connection, 'pairing_failure')
+                    def on_pairing_failure(*_: Any) -> None:
+                        security_result.set_result('pairing_failure')
+
+                    @watcher.on(connection, 'disconnection')
+                    def on_disconnection(*_: Any) -> None:
+                        security_result.set_result('connection_died')
+
+                    if (
+                        connection.transport == BT_LE_TRANSPORT
+                        and connection.role == BT_PERIPHERAL_ROLE
+                    ):
+                        connection.request_pairing()
+                    else:
+                        await connection.pair()
+
+                    result = await security_result
+
+                self.log.debug(f'Pairing session complete, status={result}')
+                if result != 'success':
+                    return SecureResponse(**{result: empty_pb2.Empty()})
             except asyncio.CancelledError:
                 self.log.warning("Connection died during encryption")
                 return SecureResponse(connection_died=empty_pb2.Empty())
@@ -369,6 +386,7 @@
             str
         ] = asyncio.get_running_loop().create_future()
         authenticate_task: Optional[asyncio.Future[None]] = None
+        pair_task: Optional[asyncio.Future[None]] = None
 
         async def authenticate() -> None:
             assert connection
@@ -415,6 +433,10 @@
                 if authenticate_task is None:
                     authenticate_task = asyncio.create_task(authenticate())
 
+        def pair(*_: Any) -> None:
+            if self.need_pairing(connection, level):
+                pair_task = asyncio.create_task(connection.pair())
+
         listeners: Dict[str, Callable[..., None]] = {
             'disconnection': set_failure('connection_died'),
             'pairing_failure': set_failure('pairing_failure'),
@@ -425,6 +447,7 @@
             'connection_encryption_change': on_encryption_change,
             'classic_pairing': try_set_success,
             'classic_pairing_failure': set_failure('pairing_failure'),
+            'security_request': pair,
         }
 
         # register event handlers
@@ -452,6 +475,15 @@
                 pass
             self.log.debug('Authenticated')
 
+        # wait for `pair` to finish if any
+        if pair_task is not None:
+            self.log.debug('Wait for authentication...')
+            try:
+                await pair_task  # type: ignore
+            except:
+                pass
+            self.log.debug('paired')
+
         return WaitSecurityResponse(**kwargs)
 
     def reached_security_level(
@@ -523,7 +555,7 @@
         self.log.debug(f"DeleteBond: {address}")
 
         if self.device.keystore is not None:
-            with suppress(KeyError):
+            with contextlib.suppress(KeyError):
                 await self.device.keystore.delete(str(address))
 
         return empty_pb2.Empty()
diff --git a/bumble/smp.py b/bumble/smp.py
index 55b8359..f8bba40 100644
--- a/bumble/smp.py
+++ b/bumble/smp.py
@@ -37,6 +37,7 @@
     Optional,
     Tuple,
     Type,
+    cast,
 )
 
 from pyee import EventEmitter
@@ -1771,7 +1772,26 @@
         cid = SMP_BR_CID if connection.transport == BT_BR_EDR_TRANSPORT else SMP_CID
         connection.send_l2cap_pdu(cid, command.to_bytes())
 
+    def on_smp_security_request_command(
+        self, connection: Connection, request: SMP_Security_Request_Command
+    ) -> None:
+        connection.emit('security_request', request.auth_req)
+
     def on_smp_pdu(self, connection: Connection, pdu: bytes) -> None:
+        # Parse the L2CAP payload into an SMP Command object
+        command = SMP_Command.from_bytes(pdu)
+        logger.debug(
+            f'<<< Received SMP Command on connection [0x{connection.handle:04X}] '
+            f'{connection.peer_address}: {command}'
+        )
+
+        # Security request is more than just pairing, so let applications handle them
+        if command.code == SMP_SECURITY_REQUEST_COMMAND:
+            self.on_smp_security_request_command(
+                connection, cast(SMP_Security_Request_Command, command)
+            )
+            return
+
         # Look for a session with this connection, and create one if none exists
         if not (session := self.sessions.get(connection.handle)):
             if connection.role == BT_CENTRAL_ROLE:
@@ -1782,13 +1802,6 @@
             )
             self.sessions[connection.handle] = session
 
-        # Parse the L2CAP payload into an SMP Command object
-        command = SMP_Command.from_bytes(pdu)
-        logger.debug(
-            f'<<< Received SMP Command on connection [0x{connection.handle:04X}] '
-            f'{connection.peer_address}: {command}'
-        )
-
         # Delegate the handling of the command to the session
         session.on_smp_command(command)
 
diff --git a/bumble/transport/android_emulator.py b/bumble/transport/android_emulator.py
index 5ef0047..8d19a9e 100644
--- a/bumble/transport/android_emulator.py
+++ b/bumble/transport/android_emulator.py
@@ -18,6 +18,8 @@
 import logging
 import grpc.aio
 
+from typing import Optional, Union
+
 from .common import PumpedTransport, PumpedPacketSource, PumpedPacketSink, Transport
 
 # pylint: disable=no-name-in-module
@@ -33,7 +35,7 @@
 
 
 # -----------------------------------------------------------------------------
-async def open_android_emulator_transport(spec: str | None) -> Transport:
+async def open_android_emulator_transport(spec: Optional[str]) -> Transport:
     '''
     Open a transport connection to an Android emulator via its gRPC interface.
     The parameter string has this syntax:
@@ -82,7 +84,7 @@
     logger.debug(f'connecting to gRPC server at {server_address}')
     channel = grpc.aio.insecure_channel(server_address)
 
-    service: EmulatedBluetoothServiceStub | VhciForwardingServiceStub
+    service: Union[EmulatedBluetoothServiceStub, VhciForwardingServiceStub]
     if mode == 'host':
         # Connect as a host
         service = EmulatedBluetoothServiceStub(channel)
@@ -95,10 +97,13 @@
         raise ValueError('invalid mode')
 
     # Create the transport object
-    transport = PumpedTransport(
-        PumpedPacketSource(hci_device.read),
-        PumpedPacketSink(hci_device.write),
-        channel.close,
+    class EmulatorTransport(PumpedTransport):
+        async def close(self):
+            await super().close()
+            await channel.close()
+
+    transport = EmulatorTransport(
+        PumpedPacketSource(hci_device.read), PumpedPacketSink(hci_device.write)
     )
     transport.start()
 
diff --git a/bumble/transport/android_netsim.py b/bumble/transport/android_netsim.py
index 76a7385..e9d36cd 100644
--- a/bumble/transport/android_netsim.py
+++ b/bumble/transport/android_netsim.py
@@ -18,11 +18,12 @@
 import asyncio
 import atexit
 import logging
-import grpc.aio
 import os
 import pathlib
 import sys
-from typing import Optional
+from typing import Dict, Optional
+
+import grpc.aio
 
 from .common import (
     ParserSource,
@@ -33,8 +34,8 @@
 )
 
 # pylint: disable=no-name-in-module
-from .grpc_protobuf.packet_streamer_pb2_grpc import PacketStreamerStub
 from .grpc_protobuf.packet_streamer_pb2_grpc import (
+    PacketStreamerStub,
     PacketStreamerServicer,
     add_PacketStreamerServicer_to_server,
 )
@@ -43,6 +44,7 @@
 from .grpc_protobuf.startup_pb2 import Chip, ChipInfo
 from .grpc_protobuf.common_pb2 import ChipKind
 
+
 # -----------------------------------------------------------------------------
 # Logging
 # -----------------------------------------------------------------------------
@@ -74,14 +76,20 @@
 
 
 # -----------------------------------------------------------------------------
-def find_grpc_port() -> int:
+def ini_file_name(instance_number: int) -> str:
+    suffix = f'_{instance_number}' if instance_number > 0 else ''
+    return f'netsim{suffix}.ini'
+
+
+# -----------------------------------------------------------------------------
+def find_grpc_port(instance_number: int) -> int:
     if not (ini_dir := get_ini_dir()):
         logger.debug('no known directory for .ini file')
         return 0
 
-    ini_file = ini_dir / 'netsim.ini'
+    ini_file = ini_dir / ini_file_name(instance_number)
+    logger.debug(f'Looking for .ini file at {ini_file}')
     if ini_file.is_file():
-        logger.debug(f'Found .ini file at {ini_file}')
         with open(ini_file, 'r') as ini_file_data:
             for line in ini_file_data.readlines():
                 if '=' in line:
@@ -90,12 +98,14 @@
                         logger.debug(f'gRPC port = {value}')
                         return int(value)
 
+        logger.debug('no grpc.port property found in .ini file')
+
     # Not found
     return 0
 
 
 # -----------------------------------------------------------------------------
-def publish_grpc_port(grpc_port) -> bool:
+def publish_grpc_port(grpc_port: int, instance_number: int) -> bool:
     if not (ini_dir := get_ini_dir()):
         logger.debug('no known directory for .ini file')
         return False
@@ -104,7 +114,7 @@
         logger.debug('ini directory does not exist')
         return False
 
-    ini_file = ini_dir / 'netsim.ini'
+    ini_file = ini_dir / ini_file_name(instance_number)
     try:
         ini_file.write_text(f'grpc.port={grpc_port}\n')
         logger.debug(f"published gRPC port at {ini_file}")
@@ -122,14 +132,15 @@
 
 # -----------------------------------------------------------------------------
 async def open_android_netsim_controller_transport(
-    server_host: str | None, server_port: int
+    server_host: Optional[str], server_port: int, options: Dict[str, str]
 ) -> Transport:
     if not server_port:
         raise ValueError('invalid port')
     if server_host == '_' or not server_host:
         server_host = 'localhost'
 
-    if not publish_grpc_port(server_port):
+    instance_number = int(options.get('instance', "0"))
+    if not publish_grpc_port(server_port, instance_number):
         logger.warning("unable to publish gRPC port")
 
     class HciDevice:
@@ -186,15 +197,12 @@
                 logger.debug(f'<<< PACKET: {data.hex()}')
                 self.on_data_received(data)
 
-        def send_packet(self, data):
-            async def send():
-                await self.context.write(
-                    PacketResponse(
-                        hci_packet=HCIPacket(packet_type=data[0], packet=data[1:])
-                    )
+        async def send_packet(self, data):
+            return await self.context.write(
+                PacketResponse(
+                    hci_packet=HCIPacket(packet_type=data[0], packet=data[1:])
                 )
-
-            self.loop.create_task(send())
+            )
 
         def terminate(self):
             self.task.cancel()
@@ -228,17 +236,17 @@
                 logger.debug('gRPC server cancelled')
                 await self.grpc_server.stop(None)
 
-        def on_packet(self, packet):
+        async def send_packet(self, packet):
             if not self.device:
                 logger.debug('no device, dropping packet')
                 return
 
-            self.device.send_packet(packet)
+            return await self.device.send_packet(packet)
 
         async def StreamPackets(self, _request_iterator, context):
             logger.debug('StreamPackets request')
 
-            # Check that we won't already have a device
+            # Check that we don't already have a device
             if self.device:
                 logger.debug('busy, already serving a device')
                 return PacketResponse(error='Busy')
@@ -261,15 +269,42 @@
     await server.start()
     asyncio.get_running_loop().create_task(server.serve())
 
-    class GrpcServerTransport(Transport):
-        async def close(self):
-            await super().close()
-
-    return GrpcServerTransport(server, server)
+    sink = PumpedPacketSink(server.send_packet)
+    sink.start()
+    return Transport(server, sink)
 
 
 # -----------------------------------------------------------------------------
-async def open_android_netsim_host_transport(server_host, server_port, options):
+async def open_android_netsim_host_transport_with_address(
+    server_host: Optional[str],
+    server_port: int,
+    options: Optional[Dict[str, str]] = None,
+):
+    if server_host == '_' or not server_host:
+        server_host = 'localhost'
+
+    if not server_port:
+        # Look for the gRPC config in a .ini file
+        instance_number = 0 if options is None else int(options.get('instance', '0'))
+        server_port = find_grpc_port(instance_number)
+        if not server_port:
+            raise RuntimeError('gRPC server port not found')
+
+    # Connect to the gRPC server
+    server_address = f'{server_host}:{server_port}'
+    logger.debug(f'Connecting to gRPC server at {server_address}')
+    channel = grpc.aio.insecure_channel(server_address)
+
+    return await open_android_netsim_host_transport_with_channel(
+        channel,
+        options,
+    )
+
+
+# -----------------------------------------------------------------------------
+async def open_android_netsim_host_transport_with_channel(
+    channel, options: Optional[Dict[str, str]] = None
+):
     # Wrapper for I/O operations
     class HciDevice:
         def __init__(self, name, manufacturer, hci_device):
@@ -288,10 +323,12 @@
         async def read(self):
             response = await self.hci_device.read()
             response_type = response.WhichOneof('response_type')
+
             if response_type == 'error':
                 logger.warning(f'received error: {response.error}')
                 raise RuntimeError(response.error)
-            elif response_type == 'hci_packet':
+
+            if response_type == 'hci_packet':
                 return (
                     bytes([response.hci_packet.packet_type])
                     + response.hci_packet.packet
@@ -306,24 +343,9 @@
                 )
             )
 
-    name = options.get('name', DEFAULT_NAME)
+    name = DEFAULT_NAME if options is None else options.get('name', DEFAULT_NAME)
     manufacturer = DEFAULT_MANUFACTURER
 
-    if server_host == '_' or not server_host:
-        server_host = 'localhost'
-
-    if not server_port:
-        # Look for the gRPC config in a .ini file
-        server_host = 'localhost'
-        server_port = find_grpc_port()
-        if not server_port:
-            raise RuntimeError('gRPC server port not found')
-
-    # Connect to the gRPC server
-    server_address = f'{server_host}:{server_port}'
-    logger.debug(f'Connecting to gRPC server at {server_address}')
-    channel = grpc.aio.insecure_channel(server_address)
-
     # Connect as a host
     service = PacketStreamerStub(channel)
     hci_device = HciDevice(
@@ -334,10 +356,14 @@
     await hci_device.start()
 
     # Create the transport object
-    transport = PumpedTransport(
+    class GrpcTransport(PumpedTransport):
+        async def close(self):
+            await super().close()
+            await channel.close()
+
+    transport = GrpcTransport(
         PumpedPacketSource(hci_device.read),
         PumpedPacketSink(hci_device.write),
-        channel.close,
     )
     transport.start()
 
@@ -345,7 +371,7 @@
 
 
 # -----------------------------------------------------------------------------
-async def open_android_netsim_transport(spec):
+async def open_android_netsim_transport(spec: Optional[str]) -> Transport:
     '''
     Open a transport connection as a client or server, implementing Android's `netsim`
     simulator protocol over gRPC.
@@ -359,6 +385,11 @@
         to connect *to* a netsim server (netsim is the controller), or accept
         connections *as* a netsim-compatible server.
 
+      instance=<n>
+        Specifies an instance number, with <n> > 0. This is used to determine which
+        .init file to use. In `host` mode, it is ignored when the <host>:<port>
+        specifier is present, since in that case no .ini file is used.
+
     In `host` mode:
       The <host>:<port> part is optional. When not specified, the transport
       looks for a netsim .ini file, from which it will read the `grpc.backend.port`
@@ -387,14 +418,15 @@
     params = spec.split(',') if spec else []
     if params and ':' in params[0]:
         # Explicit <host>:<port>
-        host, port = params[0].split(':')
+        host, port_str = params[0].split(':')
+        port = int(port_str)
         params_offset = 1
     else:
         host = None
         port = 0
         params_offset = 0
 
-    options = {}
+    options: Dict[str, str] = {}
     for param in params[params_offset:]:
         if '=' not in param:
             raise ValueError('invalid parameter, expected <name>=<value>')
@@ -403,10 +435,12 @@
 
     mode = options.get('mode', 'host')
     if mode == 'host':
-        return await open_android_netsim_host_transport(host, port, options)
+        return await open_android_netsim_host_transport_with_address(
+            host, port, options
+        )
     if mode == 'controller':
         if host is None:
             raise ValueError('<host>:<port> missing')
-        return await open_android_netsim_controller_transport(host, port)
+        return await open_android_netsim_controller_transport(host, port, options)
 
     raise ValueError('invalid mode option')
diff --git a/bumble/transport/common.py b/bumble/transport/common.py
index c030308..2786a75 100644
--- a/bumble/transport/common.py
+++ b/bumble/transport/common.py
@@ -339,8 +339,9 @@
                 try:
                     packet = await self.receive_function()
                     self.parser.feed_data(packet)
-                except asyncio.exceptions.CancelledError:
+                except asyncio.CancelledError:
                     logger.debug('source pump task done')
+                    self.terminated.set_result(None)
                     break
                 except Exception as error:
                     logger.warning(f'exception while waiting for packet: {error}')
@@ -370,7 +371,7 @@
                 try:
                     packet = await self.packet_queue.get()
                     await self.send_function(packet)
-                except asyncio.exceptions.CancelledError:
+                except asyncio.CancelledError:
                     logger.debug('sink pump task done')
                     break
                 except Exception as error:
@@ -393,19 +394,13 @@
         self,
         source: PumpedPacketSource,
         sink: PumpedPacketSink,
-        close_function,
     ) -> None:
         super().__init__(source, sink)
-        self.close_function = close_function
 
     def start(self) -> None:
         self.source.start()
         self.sink.start()
 
-    async def close(self) -> None:
-        await super().close()
-        await self.close_function()
-
 
 # -----------------------------------------------------------------------------
 class SnoopingTransport(Transport):
diff --git a/bumble/transport/hci_socket.py b/bumble/transport/hci_socket.py
index 9891c5b..df9e885 100644
--- a/bumble/transport/hci_socket.py
+++ b/bumble/transport/hci_socket.py
@@ -23,6 +23,8 @@
 import ctypes
 import collections
 
+from typing import Optional
+
 from .common import Transport, ParserSource
 
 
@@ -33,7 +35,7 @@
 
 
 # -----------------------------------------------------------------------------
-async def open_hci_socket_transport(spec: str | None) -> Transport:
+async def open_hci_socket_transport(spec: Optional[str]) -> Transport:
     '''
     Open an HCI Socket (only available on some platforms).
     The parameter string is either empty (to use the first/default Bluetooth adapter)
@@ -45,9 +47,9 @@
     # Create a raw HCI socket
     try:
         hci_socket = socket.socket(
-            socket.AF_BLUETOOTH,
-            socket.SOCK_RAW | socket.SOCK_NONBLOCK,
-            socket.BTPROTO_HCI,  # type: ignore
+            socket.AF_BLUETOOTH,  # type: ignore[attr-defined]
+            socket.SOCK_RAW | socket.SOCK_NONBLOCK,  # type: ignore[attr-defined]
+            socket.BTPROTO_HCI,  # type: ignore[attr-defined]
         )
     except AttributeError as error:
         # Not supported on this platform
@@ -78,7 +80,7 @@
     bind_address = struct.pack(
         # pylint: disable=no-member
         '<HHH',
-        socket.AF_BLUETOOTH,
+        socket.AF_BLUETOOTH,  # type: ignore[attr-defined]
         adapter_index,
         HCI_CHANNEL_USER,
     )
diff --git a/bumble/transport/pty.py b/bumble/transport/pty.py
index 7765b09..2f46e75 100644
--- a/bumble/transport/pty.py
+++ b/bumble/transport/pty.py
@@ -23,6 +23,8 @@
 import os
 import logging
 
+from typing import Optional
+
 from .common import Transport, StreamPacketSource, StreamPacketSink
 
 # -----------------------------------------------------------------------------
@@ -32,7 +34,7 @@
 
 
 # -----------------------------------------------------------------------------
-async def open_pty_transport(spec: str | None) -> Transport:
+async def open_pty_transport(spec: Optional[str]) -> Transport:
     '''
     Open a PTY transport.
     The parameter string may be empty, or a path name where a symbolic link
diff --git a/bumble/transport/vhci.py b/bumble/transport/vhci.py
index 5795840..2b19085 100644
--- a/bumble/transport/vhci.py
+++ b/bumble/transport/vhci.py
@@ -17,6 +17,8 @@
 # -----------------------------------------------------------------------------
 import logging
 
+from typing import Optional
+
 from .common import Transport
 from .file import open_file_transport
 
@@ -27,7 +29,7 @@
 
 
 # -----------------------------------------------------------------------------
-async def open_vhci_transport(spec: str | None) -> Transport:
+async def open_vhci_transport(spec: Optional[str]) -> Transport:
     '''
     Open a VHCI transport (only available on some platforms).
     The parameter string is either empty (to use the default VHCI device
diff --git a/bumble/transport/ws_client.py b/bumble/transport/ws_client.py
index facd1c9..902001e 100644
--- a/bumble/transport/ws_client.py
+++ b/bumble/transport/ws_client.py
@@ -31,19 +31,21 @@
     '''
     Open a WebSocket client transport.
     The parameter string has this syntax:
-    <remote-host>:<remote-port>
+    <websocket-url>
 
-    Example: 127.0.0.1:9001
+    Example: ws://localhost:7681/v1/websocket/bt
     '''
 
-    remote_host, remote_port = spec.split(':')
-    uri = f'ws://{remote_host}:{remote_port}'
-    websocket = await websockets.client.connect(uri)
+    websocket = await websockets.client.connect(spec)
 
-    transport = PumpedTransport(
+    class WsTransport(PumpedTransport):
+        async def close(self):
+            await super().close()
+            await websocket.close()
+
+    transport = WsTransport(
         PumpedPacketSource(websocket.recv),
         PumpedPacketSink(websocket.send),
-        websocket.close,
     )
     transport.start()
     return transport
diff --git a/bumble/utils.py b/bumble/utils.py
index 8a55684..dc03725 100644
--- a/bumble/utils.py
+++ b/bumble/utils.py
@@ -15,12 +15,24 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+from __future__ import annotations
 import asyncio
 import logging
 import traceback
 import collections
 import sys
-from typing import Awaitable, Set, TypeVar
+from typing import (
+    Awaitable,
+    Set,
+    TypeVar,
+    List,
+    Tuple,
+    Callable,
+    Any,
+    Optional,
+    Union,
+    overload,
+)
 from functools import wraps
 from pyee import EventEmitter
 
@@ -65,6 +77,102 @@
 
 
 # -----------------------------------------------------------------------------
+_Handler = TypeVar('_Handler', bound=Callable)
+
+
+class EventWatcher:
+    '''A wrapper class to control the lifecycle of event handlers better.
+
+    Usage:
+    ```
+    watcher = EventWatcher()
+
+    def on_foo():
+        ...
+    watcher.on(emitter, 'foo', on_foo)
+
+    @watcher.on(emitter, 'bar')
+    def on_bar():
+        ...
+
+    # Close all event handlers watching through this watcher
+    watcher.close()
+    ```
+
+    As context:
+    ```
+    with contextlib.closing(EventWatcher()) as context:
+        @context.on(emitter, 'foo')
+        def on_foo():
+            ...
+    # on_foo() has been removed here!
+    ```
+    '''
+
+    handlers: List[Tuple[EventEmitter, str, Callable[..., Any]]]
+
+    def __init__(self) -> None:
+        self.handlers = []
+
+    @overload
+    def on(self, emitter: EventEmitter, event: str) -> Callable[[_Handler], _Handler]:
+        ...
+
+    @overload
+    def on(self, emitter: EventEmitter, event: str, handler: _Handler) -> _Handler:
+        ...
+
+    def on(
+        self, emitter: EventEmitter, event: str, handler: Optional[_Handler] = None
+    ) -> Union[_Handler, Callable[[_Handler], _Handler]]:
+        '''Watch an event until the context is closed.
+
+        Args:
+            emitter: EventEmitter to watch
+            event: Event name
+            handler: (Optional) Event handler. When nothing is passed, this method works as a decorator.
+        '''
+
+        def wrapper(f: _Handler) -> _Handler:
+            self.handlers.append((emitter, event, f))
+            emitter.on(event, f)
+            return f
+
+        return wrapper if handler is None else wrapper(handler)
+
+    @overload
+    def once(self, emitter: EventEmitter, event: str) -> Callable[[_Handler], _Handler]:
+        ...
+
+    @overload
+    def once(self, emitter: EventEmitter, event: str, handler: _Handler) -> _Handler:
+        ...
+
+    def once(
+        self, emitter: EventEmitter, event: str, handler: Optional[_Handler] = None
+    ) -> Union[_Handler, Callable[[_Handler], _Handler]]:
+        '''Watch an event for once.
+
+        Args:
+            emitter: EventEmitter to watch
+            event: Event name
+            handler: (Optional) Event handler. When nothing passed, this method works as a decorator.
+        '''
+
+        def wrapper(f: _Handler) -> _Handler:
+            self.handlers.append((emitter, event, f))
+            emitter.once(event, f)
+            return f
+
+        return wrapper if handler is None else wrapper(handler)
+
+    def close(self) -> None:
+        for emitter, event, handler in self.handlers:
+            if handler in emitter.listeners(event):
+                emitter.remove_listener(event, handler)
+
+
+# -----------------------------------------------------------------------------
 _T = TypeVar('_T')
 
 
diff --git a/rust/Cargo.lock b/rust/Cargo.lock
index bd168dc..c2d0cd3 100644
--- a/rust/Cargo.lock
+++ b/rust/Cargo.lock
@@ -131,6 +131,16 @@
 checksum = "b4682ae6287fcf752ecaabbfcc7b6f9b72aa33933dc23a554d853aea8eea8635"
 
 [[package]]
+name = "bstr"
+version = "1.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c2f7349907b712260e64b0afe2f84692af14a454be26187d9df565c7f69266a"
+dependencies = [
+ "memchr",
+ "serde",
+]
+
+[[package]]
 name = "bumble"
 version = "0.1.0"
 dependencies = [
@@ -138,7 +148,9 @@
  "clap 4.4.1",
  "directories",
  "env_logger",
+ "file-header",
  "futures",
+ "globset",
  "hex",
  "itertools",
  "lazy_static",
@@ -273,6 +285,73 @@
 checksum = "e496a50fda8aacccc86d7529e2c1e0892dbd0f898a6b5645b5561b89c3210efa"
 
 [[package]]
+name = "crossbeam"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2801af0d36612ae591caa9568261fddce32ce6e08a7275ea334a06a4ad021a2c"
+dependencies = [
+ "cfg-if",
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-epoch",
+ "crossbeam-queue",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a33c2bf77f2df06183c3aa30d1e96c0695a313d4f9c453cc3762a6db39f99200"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce6fd6f855243022dcecf8702fef0c297d4338e226845fe067f6341ad9fa0cef"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae211234986c545741a7dc064309f67ee1e5ad243d0e48335adc0484d960bcc7"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+ "crossbeam-utils",
+ "memoffset 0.9.0",
+ "scopeguard",
+]
+
+[[package]]
+name = "crossbeam-queue"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d1cfb3ea8a53f37c40dea2c7bedcbd88bdfae54f5e2175d6ecaff1c988353add"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a22b2d63d4d1dc0b7f1b6b2747dd0088008a9be28b6ddf0b1e7d335e3037294"
+dependencies = [
+ "cfg-if",
+]
+
+[[package]]
 name = "directories"
 version = "5.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -349,6 +428,19 @@
 checksum = "6999dc1837253364c2ebb0704ba97994bd874e8f195d665c50b7548f6ea92764"
 
 [[package]]
+name = "file-header"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5568149106e77ae33bc3a2c3ef3839cbe63ffa4a8dd4a81612a6f9dfdbc2e9f"
+dependencies = [
+ "crossbeam",
+ "lazy_static",
+ "license",
+ "thiserror",
+ "walkdir",
+]
+
+[[package]]
 name = "fnv"
 version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -485,6 +577,19 @@
 checksum = "6fb8d784f27acf97159b40fc4db5ecd8aa23b9ad5ef69cdd136d3bc80665f0c0"
 
 [[package]]
+name = "globset"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "759c97c1e17c55525b57192c06a267cda0ac5210b222d6b82189a2338fa1c13d"
+dependencies = [
+ "aho-corasick",
+ "bstr",
+ "fnv",
+ "log",
+ "regex",
+]
+
+[[package]]
 name = "h2"
 version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -711,6 +816,17 @@
 ]
 
 [[package]]
+name = "license"
+version = "3.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b66615d42e949152327c402e03cd29dab8bff91ce470381ac2ca6d380d8d9946"
+dependencies = [
+ "reword",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
 name = "linux-raw-sys"
 version = "0.4.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -757,6 +873,15 @@
 ]
 
 [[package]]
+name = "memoffset"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a634b1c61a95585bd15607c6ab0c4e5b226e695ff2800ba0cdccddf208c406c"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
 name = "mime"
 version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1201,6 +1326,15 @@
 ]
 
 [[package]]
+name = "reword"
+version = "7.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe272098dce9ed76b479995953f748d1851261390b08f8a0ff619c885a1f0765"
+dependencies = [
+ "unicode-segmentation",
+]
+
+[[package]]
 name = "rusb"
 version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1242,6 +1376,15 @@
 checksum = "1ad4cc8da4ef723ed60bced201181d83791ad433213d8c24efffda1eec85d741"
 
 [[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
+[[package]]
 name = "schannel"
 version = "0.1.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1590,6 +1733,12 @@
 ]
 
 [[package]]
+name = "unicode-segmentation"
+version = "1.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1dd624098567895118886609431a7c3b8f516e41d30e0643f03d94592a147e36"
+
+[[package]]
 name = "unindent"
 version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1619,6 +1768,16 @@
 checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
 [[package]]
+name = "walkdir"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d71d857dc86794ca4c280d616f7da00d2dbfd8cd788846559a6813e6aa4b54ee"
+dependencies = [
+ "same-file",
+ "winapi-util",
+]
+
+[[package]]
 name = "want"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index 6c38c82..a553afd 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -24,6 +24,10 @@
 lazy_static = "1.4.0"
 thiserror = "1.0.41"
 
+# Dev tools
+file-header = { version = "0.1.2", optional = true }
+globset = { version = "0.4.13", optional = true }
+
 # CLI
 anyhow = { version = "1.0.71", optional = true }
 clap = { version = "4.3.3", features = ["derive"], optional = true }
@@ -53,9 +57,14 @@
 rustdoc-args = ["--generate-link-to-definition"]
 
 [[bin]]
+name = "file-header"
+path = "tools/file_header.rs"
+required-features = ["dev-tools"]
+
+[[bin]]
 name = "gen-assigned-numbers"
 path = "tools/gen_assigned_numbers.rs"
-required-features = ["bumble-codegen"]
+required-features = ["dev-tools"]
 
 [[bin]]
 name = "bumble"
@@ -71,7 +80,7 @@
 [features]
 anyhow = ["pyo3/anyhow"]
 pyo3-asyncio-attributes = ["pyo3-asyncio/attributes"]
-bumble-codegen = ["dep:anyhow"]
+dev-tools = ["dep:anyhow", "dep:clap", "dep:file-header", "dep:globset"]
 # separate feature for CLI so that dependencies don't spend time building these
 bumble-tools = ["dep:clap", "anyhow", "dep:anyhow", "dep:directories", "pyo3-asyncio-attributes", "dep:owo-colors", "dep:reqwest", "dep:rusb", "dep:log", "dep:env_logger", "dep:futures"]
 default = []
diff --git a/rust/README.md b/rust/README.md
index 23dec03..15a19b9 100644
--- a/rust/README.md
+++ b/rust/README.md
@@ -62,5 +62,5 @@
 To regenerate the assigned number tables based on the Python codebase:
 
 ```
-PYTHONPATH=.. cargo run --bin gen-assigned-numbers --features bumble-codegen
+PYTHONPATH=.. cargo run --bin gen-assigned-numbers --features dev-tools
 ```
\ No newline at end of file
diff --git a/rust/pytests/assigned_numbers.rs b/rust/pytests/assigned_numbers.rs
index 10e7f3e..7f8f1d1 100644
--- a/rust/pytests/assigned_numbers.rs
+++ b/rust/pytests/assigned_numbers.rs
@@ -1,3 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 use bumble::wrapper::{self, core::Uuid16};
 use pyo3::{intern, prelude::*, types::PyDict};
 use std::collections;
diff --git a/rust/src/adv.rs b/rust/src/adv.rs
index 8a4c979..6f84cc5 100644
--- a/rust/src/adv.rs
+++ b/rust/src/adv.rs
@@ -1,3 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 //! BLE advertisements.
 
 use crate::wrapper::assigned_numbers::{COMPANY_IDS, SERVICE_IDS};
diff --git a/rust/src/wrapper/logging.rs b/rust/src/wrapper/logging.rs
index 141cc04..bd932cb 100644
--- a/rust/src/wrapper/logging.rs
+++ b/rust/src/wrapper/logging.rs
@@ -1,3 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 //! Bumble & Python logging
 
 use pyo3::types::PyDict;
diff --git a/rust/tools/file_header.rs b/rust/tools/file_header.rs
new file mode 100644
index 0000000..fb3286d
--- /dev/null
+++ b/rust/tools/file_header.rs
@@ -0,0 +1,78 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use anyhow::anyhow;
+use clap::Parser as _;
+use file_header::{
+    add_headers_recursively, check_headers_recursively,
+    license::spdx::{YearCopyrightOwnerValue, APACHE_2_0},
+};
+use globset::{Glob, GlobSet, GlobSetBuilder};
+use std::{env, path::PathBuf};
+
+fn main() -> anyhow::Result<()> {
+    let rust_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR")?);
+    let ignore_globset = ignore_globset()?;
+    // Note: when adding headers, there is a bug where the line spacing is off for Apache 2.0 (see https://github.com/spdx/license-list-XML/issues/2127)
+    let header = APACHE_2_0.build_header(YearCopyrightOwnerValue::new(2023, "Google LLC".into()));
+
+    let cli = Cli::parse();
+
+    match cli.subcommand {
+        Subcommand::CheckAll => {
+            let result =
+                check_headers_recursively(&rust_dir, |p| !ignore_globset.is_match(p), header, 4)?;
+            if result.has_failure() {
+                return Err(anyhow!(
+                    "The following files do not have headers: {result:?}"
+                ));
+            }
+        }
+        Subcommand::AddAll => {
+            let files_with_new_header =
+                add_headers_recursively(&rust_dir, |p| !ignore_globset.is_match(p), header)?;
+            files_with_new_header
+                .iter()
+                .for_each(|path| println!("Added header to: {path:?}"));
+        }
+    }
+    Ok(())
+}
+
+fn ignore_globset() -> anyhow::Result<GlobSet> {
+    Ok(GlobSetBuilder::new()
+        .add(Glob::new("**/.idea/**")?)
+        .add(Glob::new("**/target/**")?)
+        .add(Glob::new("**/.gitignore")?)
+        .add(Glob::new("**/CHANGELOG.md")?)
+        .add(Glob::new("**/Cargo.lock")?)
+        .add(Glob::new("**/Cargo.toml")?)
+        .add(Glob::new("**/README.md")?)
+        .add(Glob::new("*.bin")?)
+        .build()?)
+}
+
+#[derive(clap::Parser)]
+struct Cli {
+    #[clap(subcommand)]
+    subcommand: Subcommand,
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+enum Subcommand {
+    /// Checks if a license is present in files that are not in the ignore list.
+    CheckAll,
+    /// Adds a license as needed to files that are not in the ignore list.
+    AddAll,
+}
diff --git a/setup.cfg b/setup.cfg
index 74a90e0..1ca73c7 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -36,6 +36,10 @@
     bt-test-interfaces >= 0.0.2; platform_system!='Emscripten'
     click == 8.1.3; platform_system!='Emscripten'
     cryptography == 39; platform_system!='Emscripten'
+    # Pyodide bundles a version of cryptography that is built for wasm, which may not match the
+    # versions available on PyPI. Relax the version requirement since it's better than being
+    # completely unable to import the package in case of version mismatch.
+    cryptography >= 39.0; platform_system=='Emscripten'
     grpcio == 1.57.0; platform_system!='Emscripten'
     humanize >= 4.6.0; platform_system!='Emscripten'
     libusb1 >= 2.0.1; platform_system!='Emscripten'
@@ -84,7 +88,7 @@
     black == 22.10
     grpcio-tools >= 1.57.0
     invoke >= 1.7.3
-    mypy == 1.2.0
+    mypy == 1.5.0
     nox >= 2022
     pylint == 2.15.8
     types-appdirs >= 1.4.3
diff --git a/tests/gatt_test.py b/tests/gatt_test.py
index dd0277e..d9f6d60 100644
--- a/tests/gatt_test.py
+++ b/tests/gatt_test.py
@@ -891,10 +891,10 @@
 
 
 # -----------------------------------------------------------------------------
-def test_attribute_string_to_permissions():
-    assert Attribute.string_to_permissions('READABLE') == 1
-    assert Attribute.string_to_permissions('WRITEABLE') == 2
-    assert Attribute.string_to_permissions('READABLE,WRITEABLE') == 3
+def test_permissions_from_string():
+    assert Attribute.Permissions.from_string('READABLE') == 1
+    assert Attribute.Permissions.from_string('WRITEABLE') == 2
+    assert Attribute.Permissions.from_string('READABLE,WRITEABLE') == 3
 
 
 # -----------------------------------------------------------------------------
diff --git a/tests/keystore_test.py b/tests/keystore_test.py
index 2e73039..2a3d48d 100644
--- a/tests/keystore_test.py
+++ b/tests/keystore_test.py
@@ -18,6 +18,8 @@
 import asyncio
 import json
 import logging
+import pathlib
+import pytest
 import tempfile
 import os
 
@@ -83,87 +85,95 @@
 
 
 # -----------------------------------------------------------------------------
-async def test_basic():
-    with tempfile.NamedTemporaryFile(mode="r+", encoding='utf-8') as file:
-        keystore = JsonKeyStore('my_namespace', file.name)
+@pytest.fixture
+def temporary_file():
+    file = tempfile.NamedTemporaryFile(delete=False)
+    file.close()
+    yield file.name
+    pathlib.Path(file.name).unlink()
+
+
+# -----------------------------------------------------------------------------
+async def test_basic(temporary_file):
+    with open(temporary_file, mode='w', encoding='utf-8') as file:
         file.write("{}")
         file.flush()
 
-        keys = await keystore.get_all()
-        assert len(keys) == 0
+    keystore = JsonKeyStore('my_namespace', temporary_file)
 
-        keys = PairingKeys()
-        await keystore.update('foo', keys)
-        foo = await keystore.get('foo')
-        assert foo is not None
-        assert foo.ltk is None
-        ltk = bytes([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
-        keys.ltk = PairingKeys.Key(ltk)
-        await keystore.update('foo', keys)
-        foo = await keystore.get('foo')
-        assert foo is not None
-        assert foo.ltk is not None
-        assert foo.ltk.value == ltk
+    keys = await keystore.get_all()
+    assert len(keys) == 0
 
-        file.flush()
-        with open(file.name, "r", encoding="utf-8") as json_file:
-            json_data = json.load(json_file)
-            assert 'my_namespace' in json_data
-            assert 'foo' in json_data['my_namespace']
-            assert 'ltk' in json_data['my_namespace']['foo']
+    keys = PairingKeys()
+    await keystore.update('foo', keys)
+    foo = await keystore.get('foo')
+    assert foo is not None
+    assert foo.ltk is None
+    ltk = bytes([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
+    keys.ltk = PairingKeys.Key(ltk)
+    await keystore.update('foo', keys)
+    foo = await keystore.get('foo')
+    assert foo is not None
+    assert foo.ltk is not None
+    assert foo.ltk.value == ltk
+
+    with open(file.name, "r", encoding="utf-8") as json_file:
+        json_data = json.load(json_file)
+        assert 'my_namespace' in json_data
+        assert 'foo' in json_data['my_namespace']
+        assert 'ltk' in json_data['my_namespace']['foo']
 
 
 # -----------------------------------------------------------------------------
-async def test_parsing():
-    with tempfile.NamedTemporaryFile(mode="w", encoding='utf-8') as file:
-        keystore = JsonKeyStore('my_namespace', file.name)
+async def test_parsing(temporary_file):
+    with open(temporary_file, mode='w', encoding='utf-8') as file:
         file.write(JSON1)
         file.flush()
 
-        foo = await keystore.get('14:7D:DA:4E:53:A8/P')
-        assert foo is not None
-        assert foo.ltk.value == bytes.fromhex('d1897ee10016eb1a08e4e037fd54c683')
+    keystore = JsonKeyStore('my_namespace', file.name)
+    foo = await keystore.get('14:7D:DA:4E:53:A8/P')
+    assert foo is not None
+    assert foo.ltk.value == bytes.fromhex('d1897ee10016eb1a08e4e037fd54c683')
 
 
 # -----------------------------------------------------------------------------
-async def test_default_namespace():
-    with tempfile.NamedTemporaryFile(mode="w", encoding='utf-8') as file:
-        keystore = JsonKeyStore(None, file.name)
+async def test_default_namespace(temporary_file):
+    with open(temporary_file, mode='w', encoding='utf-8') as file:
         file.write(JSON1)
         file.flush()
 
-        all_keys = await keystore.get_all()
-        assert len(all_keys) == 1
-        name, keys = all_keys[0]
-        assert name == '14:7D:DA:4E:53:A8/P'
-        assert keys.irk.value == bytes.fromhex('e7b2543b206e4e46b44f9e51dad22bd1')
+    keystore = JsonKeyStore(None, file.name)
+    all_keys = await keystore.get_all()
+    assert len(all_keys) == 1
+    name, keys = all_keys[0]
+    assert name == '14:7D:DA:4E:53:A8/P'
+    assert keys.irk.value == bytes.fromhex('e7b2543b206e4e46b44f9e51dad22bd1')
 
-    with tempfile.NamedTemporaryFile(mode="w", encoding='utf-8') as file:
-        keystore = JsonKeyStore(None, file.name)
+    with open(temporary_file, mode='w', encoding='utf-8') as file:
         file.write(JSON2)
         file.flush()
 
-        keys = PairingKeys()
-        ltk = bytes([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
-        keys.ltk = PairingKeys.Key(ltk)
-        await keystore.update('foo', keys)
-        file.flush()
-        with open(file.name, "r", encoding="utf-8") as json_file:
-            json_data = json.load(json_file)
-            assert '__DEFAULT__' in json_data
-            assert 'foo' in json_data['__DEFAULT__']
-            assert 'ltk' in json_data['__DEFAULT__']['foo']
+    keystore = JsonKeyStore(None, file.name)
+    keys = PairingKeys()
+    ltk = bytes([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
+    keys.ltk = PairingKeys.Key(ltk)
+    await keystore.update('foo', keys)
+    with open(file.name, "r", encoding="utf-8") as json_file:
+        json_data = json.load(json_file)
+        assert '__DEFAULT__' in json_data
+        assert 'foo' in json_data['__DEFAULT__']
+        assert 'ltk' in json_data['__DEFAULT__']['foo']
 
-    with tempfile.NamedTemporaryFile(mode="w", encoding='utf-8') as file:
-        keystore = JsonKeyStore(None, file.name)
+    with open(temporary_file, mode='w', encoding='utf-8') as file:
         file.write(JSON3)
         file.flush()
 
-        all_keys = await keystore.get_all()
-        assert len(all_keys) == 1
-        name, keys = all_keys[0]
-        assert name == '14:7D:DA:4E:53:A8/P'
-        assert keys.irk.value == bytes.fromhex('e7b2543b206e4e46b44f9e51dad22bd1')
+    keystore = JsonKeyStore(None, file.name)
+    all_keys = await keystore.get_all()
+    assert len(all_keys) == 1
+    name, keys = all_keys[0]
+    assert name == '14:7D:DA:4E:53:A8/P'
+    assert keys.irk.value == bytes.fromhex('e7b2543b206e4e46b44f9e51dad22bd1')
 
 
 # -----------------------------------------------------------------------------
diff --git a/tests/utils_test.py b/tests/utils_test.py
new file mode 100644
index 0000000..d6f5780
--- /dev/null
+++ b/tests/utils_test.py
@@ -0,0 +1,77 @@
+# Copyright 2021-2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import contextlib
+import logging
+import os
+
+from bumble import utils
+from pyee import EventEmitter
+from unittest.mock import MagicMock
+
+
+def test_on() -> None:
+    emitter = EventEmitter()
+    with contextlib.closing(utils.EventWatcher()) as context:
+        mock = MagicMock()
+        context.on(emitter, 'event', mock)
+
+        emitter.emit('event')
+
+    assert not emitter.listeners('event')
+    assert mock.call_count == 1
+
+
+def test_on_decorator() -> None:
+    emitter = EventEmitter()
+    with contextlib.closing(utils.EventWatcher()) as context:
+        mock = MagicMock()
+
+        @context.on(emitter, 'event')
+        def on_event(*_) -> None:
+            mock()
+
+        emitter.emit('event')
+
+    assert not emitter.listeners('event')
+    assert mock.call_count == 1
+
+
+def test_multiple_handlers() -> None:
+    emitter = EventEmitter()
+    with contextlib.closing(utils.EventWatcher()) as context:
+        mock = MagicMock()
+
+        context.once(emitter, 'a', mock)
+        context.once(emitter, 'b', mock)
+
+        emitter.emit('b', 'b')
+
+    assert not emitter.listeners('a')
+    assert not emitter.listeners('b')
+
+    mock.assert_called_once_with('b')
+
+
+# -----------------------------------------------------------------------------
+def run_tests():
+    test_on()
+    test_on_decorator()
+    test_multiple_handlers()
+
+
+# -----------------------------------------------------------------------------
+if __name__ == '__main__':
+    logging.basicConfig(level=os.environ.get('BUMBLE_LOGLEVEL', 'INFO').upper())
+    run_tests()
diff --git a/web/bumble.js b/web/bumble.js
index c5fd6a3..b1243a5 100644
--- a/web/bumble.js
+++ b/web/bumble.js
@@ -74,7 +74,6 @@
     await pyodide.loadPackage("micropip");
     await pyodide.runPythonAsync(`
         import micropip
-        await micropip.install("cryptography")
         await micropip.install("${bumblePackage}")
         package_list = micropip.list()
         print(package_list)
diff --git a/web/scanner/scanner.py b/web/scanner/scanner.py
index dd53050..c0fc456 100644
--- a/web/scanner/scanner.py
+++ b/web/scanner/scanner.py
@@ -23,7 +23,7 @@
 # -----------------------------------------------------------------------------
 class ScanEntry:
     def __init__(self, advertisement):
-        self.address = str(advertisement.address).replace("/P", "")
+        self.address = advertisement.address.to_string(False)
         self.address_type = ('Public', 'Random', 'Public Identity', 'Random Identity')[
             advertisement.address.address_type
         ]
diff --git a/web/speaker/speaker.py b/web/speaker/speaker.py
index ddc2086..d9293a4 100644
--- a/web/speaker/speaker.py
+++ b/web/speaker/speaker.py
@@ -171,7 +171,7 @@
         self.connection = connection
         connection.on('disconnection', self.on_bluetooth_disconnection)
         peer_name = '' if connection.peer_name is None else connection.peer_name
-        peer_address = str(connection.peer_address).replace('/P', '')
+        peer_address = connection.peer_address.to_string(False)
         self.emit_event(
             'connection', {'peer_name': peer_name, 'peer_address': peer_address}
         )