add support for notifying with a transient value

gbg/pairing with no distribution

bumble/att.py

@@ -700,16 +700,26 @@ class Attribute(EventEmitter):
         else:
             self.value = value
 
+    def encode_value(self, value):
+        return value
+
+    def decode_value(self, value_bytes):
+        return value_bytes
+
     def read_value(self, connection):
         if read := getattr(self.value, 'read', None):
             try:
-                return read(connection)
+                value = read(connection)
             except ATT_Error as error:
                 raise ATT_Error(error_code=error.error_code, att_handle=self.handle)
         else:
-            return self.value
+            value = self.value
+
+        return self.encode_value(value)
+
+    def write_value(self, connection, value_bytes):
+        value = self.decode_value(value_bytes)
 
-    def write_value(self, connection, value):
         if write := getattr(self.value, 'write', None):
             try:
                 write(connection, value)
@@ -721,7 +731,11 @@ class Attribute(EventEmitter):
         self.emit('write', connection, value)
 
     def __repr__(self):
-        if len(self.value) > 0:
+        if type(self.value) is bytes:
+            value_str = self.value.hex()
+        else:
+            value_str = str(self.value)
+        if value_str:
             value_string = f', value={self.value.hex()}'
         else:
             value_string = ''

bumble/device.py

@@ -1210,17 +1210,17 @@ class Device(CompositeEventEmitter):
     def add_services(self, services):
         self.gatt_server.add_services(services)
 
-    async def notify_subscriber(self, connection, attribute, force=False):
-        await self.gatt_server.notify_subscriber(connection, attribute, force)
+    async def notify_subscriber(self, connection, attribute, value=None, force=False):
+        await self.gatt_server.notify_subscriber(connection, attribute, value, force)
 
-    async def notify_subscribers(self, attribute, force=False):
-        await self.gatt_server.notify_subscribers(attribute, force)
+    async def notify_subscribers(self, attribute, value=None, force=False):
+        await self.gatt_server.notify_subscribers(attribute, value, force)
 
-    async def indicate_subscriber(self, connection, attribute, force=False):
-        await self.gatt_server.indicate_subscriber(connection, attribute, force)
+    async def indicate_subscriber(self, connection, attribute, value=None, force=False):
+        await self.gatt_server.indicate_subscriber(connection, attribute, value, force)
 
-    async def indicate_subscribers(self, attribute):
-        await self.gatt_server.indicate_subscribers(attribute)
+    async def indicate_subscribers(self, attribute, value=None, force=False):
+        await self.gatt_server.indicate_subscribers(attribute, value, force)
 
     @host_event_handler
     def on_connection(self, connection_handle, transport, peer_address, peer_resolvable_address, role, connection_parameters):

bumble/gatt.py

@@ -303,6 +303,7 @@ class CharacteristicAdapter:
     '''
     def __init__(self, characteristic):
         self.wrapped_characteristic = characteristic
+        self.subscribers = {}  # Map from subscriber to proxy subscriber
 
         if (
             asyncio.iscoroutinefunction(characteristic.read_value) and
@@ -317,11 +318,21 @@ class CharacteristicAdapter:
         if hasattr(self.wrapped_characteristic, 'subscribe'):
             self.subscribe = self.wrapped_subscribe
 
+        if hasattr(self.wrapped_characteristic, 'unsubscribe'):
+            self.unsubscribe = self.wrapped_unsubscribe
+
     def __getattr__(self, name):
         return getattr(self.wrapped_characteristic, name)
 
     def __setattr__(self, name, value):
-        if name in {'wrapped_characteristic', 'read_value', 'write_value', 'subscribe'}:
+        if name in {
+            'wrapped_characteristic',
+            'subscribers',
+            'read_value',
+            'write_value',
+            'subscribe',
+            'unsubscribe'
+        }:
             super().__setattr__(name, value)
         else:
             setattr(self.wrapped_characteristic, name, value)
@@ -345,9 +356,26 @@ class CharacteristicAdapter:
         return value
 
     def wrapped_subscribe(self, subscriber=None):
-        return self.wrapped_characteristic.subscribe(
-            None if subscriber is None else lambda value: subscriber(self.decode_value(value))
-        )
+        if subscriber is not None:
+            if subscriber in self.subscribers:
+                # We already have a proxy subscriber
+                subscriber = self.subscribers[subscriber]
+            else:
+                # Create and register a proxy that will decode the value
+                original_subscriber = subscriber
+
+                def on_change(value):
+                    original_subscriber(self.decode_value(value))
+                self.subscribers[subscriber] = on_change
+                subscriber = on_change
+
+        return self.wrapped_characteristic.subscribe(subscriber)
+
+    def wrapped_unsubscribe(self, subscriber=None):
+        if subscriber in self.subscribers:
+            subscriber = self.subscribers.pop(subscriber)
+
+        return self.wrapped_characteristic.unsubscribe(subscriber)
 
     def __str__(self):
         wrapped = str(self.wrapped_characteristic)

bumble/gatt_client.py

@@ -58,10 +58,16 @@ class AttributeProxy(EventEmitter):
         self.type             = attribute_type
 
     async def read_value(self, no_long_read=False):
-        return await self.client.read_value(self.handle, no_long_read)
+        return self.decode_value(await self.client.read_value(self.handle, no_long_read))
 
     async def write_value(self, value, with_response=False):
-        return await self.client.write_value(self.handle, value, with_response)
+        return await self.client.write_value(self.handle, self.encode_value(value), with_response)
+
+    def encode_value(self, value):
+        return value
+
+    def decode_value(self, value_bytes):
+        return value_bytes
 
     def __str__(self):
         return f'Attribute(handle=0x{self.handle:04X}, type={self.uuid})'
@@ -98,6 +104,7 @@ class CharacteristicProxy(AttributeProxy):
         self.properties             = properties
         self.descriptors            = []
         self.descriptors_discovered = False
+        self.subscribers            = {}  # Map from subscriber to proxy subscriber
 
     def get_descriptor(self, descriptor_type):
         for descriptor in self.descriptors:
@@ -108,9 +115,25 @@ class CharacteristicProxy(AttributeProxy):
         return await self.client.discover_descriptors(self)
 
     async def subscribe(self, subscriber=None):
+        if subscriber is not None:
+            if subscriber in self.subscribers:
+                # We already have a proxy subscriber
+                subscriber = self.subscribers[subscriber]
+            else:
+                # Create and register a proxy that will decode the value
+                original_subscriber = subscriber
+
+                def on_change(value):
+                    original_subscriber(self.decode_value(value))
+                self.subscribers[subscriber] = on_change
+                subscriber = on_change
+
         return await self.client.subscribe(self, subscriber)
 
     async def unsubscribe(self, subscriber=None):
+        if subscriber in self.subscribers:
+            subscriber = self.subscribers.pop(subscriber)
+
         return await self.client.unsubscribe(self, subscriber)
 
     def __str__(self):
@@ -570,12 +593,18 @@ class Client:
                 subscribers = subscriber_set.get(characteristic.handle, [])
                 if subscriber in subscribers:
                     subscribers.remove(subscriber)
+
+                    # Cleanup if we removed the last one
+                    if not subscribers:
+                        subscriber_set.remove(characteristic.handle)
         else:
             # Remove all subscribers for this attribute from the sets!
             self.notification_subscribers.pop(characteristic.handle, None)
             self.indication_subscribers.pop(characteristic.handle, None)
 
-        await self.write_value(cccd, b'\x00\x00', with_response=True)
+        if not self.notification_subscribers and not self.indication_subscribers:
+            # 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):
         '''

bumble/gatt_server.py

@@ -169,7 +169,7 @@ class Server(EventEmitter):
         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, force=False):
+    async def notify_subscriber(self, connection, attribute, value=None, force=False):
         # Check if there's a subscriber
         if not force:
             subscribers = self.subscribers.get(connection.handle)
@@ -184,8 +184,8 @@ class Server(EventEmitter):
                 logger.debug(f'not notifying, cccd={cccd.hex()}')
                 return
 
-        # Get the value
-        value = attribute.read_value(connection)
+        # Get or encode the value
+        value = attribute.read_value(connection) if value is None else attribute.encode_value(value)
 
         # Truncate if needed
         mtu = self.get_mtu(connection)
@@ -198,27 +198,9 @@ class Server(EventEmitter):
             attribute_value  = value
         )
         logger.debug(f'GATT Notify from server: [0x{connection.handle:04X}] {notification}')
-        self.send_gatt_pdu(connection.handle, notification.to_bytes())
+        self.send_gatt_pdu(connection.handle, bytes(notification))
 
-    async def notify_subscribers(self, attribute, force=False):
-        # Get all the connections for which there's at least one subscription
-        connections = [
-            connection for connection in [
-                self.device.lookup_connection(connection_handle)
-                for (connection_handle, subscribers) in self.subscribers.items()
-                if force or subscribers.get(attribute.handle)
-            ]
-            if connection is not None
-        ]
-
-        # Notify for each connection
-        if connections:
-            await asyncio.wait([
-                self.notify_subscriber(connection, attribute, force)
-                for connection in connections
-            ])
-
-    async def indicate_subscriber(self, connection, attribute, force=False):
+    async def indicate_subscriber(self, connection, attribute, value=None, force=False):
         # Check if there's a subscriber
         if not force:
             subscribers = self.subscribers.get(connection.handle)
@@ -233,8 +215,8 @@ class Server(EventEmitter):
                 logger.debug(f'not indicating, cccd={cccd.hex()}')
                 return
 
-        # Get the value
-        value = attribute.read_value(connection)
+        # Get or encode the value
+        value = attribute.read_value(connection) if value is None else attribute.encode_value(value)
 
         # Truncate if needed
         mtu = self.get_mtu(connection)
@@ -264,24 +246,31 @@ class Server(EventEmitter):
             finally:
                 self.pending_confirmations[connection.handle] = None
 
-    async def indicate_subscribers(self, attribute):
+    async def notify_or_indicate_subscribers(self, indicate, attribute, value=None, force=False):
         # Get all the connections for which there's at least one subscription
         connections = [
             connection for connection in [
                 self.device.lookup_connection(connection_handle)
                 for (connection_handle, subscribers) in self.subscribers.items()
-                if subscribers.get(attribute.handle)
+                if force or subscribers.get(attribute.handle)
             ]
             if connection is not None
         ]
 
-        # Indicate for each connection
+        # Indicate or notify for each connection
         if connections:
+            coroutine = self.indicate_subscriber if indicate else self.notify_subscriber
             await asyncio.wait([
-                self.indicate_subscriber(connection, attribute)
+                asyncio.create_task(coroutine(connection, attribute, value, force))
                 for connection in connections
             ])
 
+    async def notify_subscribers(self, attribute, value=None, force=False):
+        return await self.notify_or_indicate_subscribers(False, attribute, value, force)
+
+    async def indicate_subscribers(self, attribute, value=None, force=False):
+        return await self.notify_or_indicate_subscribers(True, attribute, value, force)
+
     def on_disconnection(self, connection):
         if connection.handle in self.mtus:
             del self.mtus[connection.handle]

bumble/helpers.py

@@ -18,6 +18,8 @@
 import logging
 from colors import color
 
+from bumble.smp import SMP_CID, SMP_Command
+
 from .core import name_or_number
 from .gatt import ATT_PDU, ATT_CID
 from .l2cap import (
@@ -73,6 +75,9 @@ class PacketTracer:
             if l2cap_pdu.cid == ATT_CID:
                 att_pdu = ATT_PDU.from_bytes(l2cap_pdu.payload)
                 self.analyzer.emit(att_pdu)
+            elif l2cap_pdu.cid == SMP_CID:
+                smp_command = SMP_Command.from_bytes(l2cap_pdu.payload)
+                self.analyzer.emit(smp_command)
             elif l2cap_pdu.cid == L2CAP_SIGNALING_CID or l2cap_pdu.cid == L2CAP_LE_SIGNALING_CID:
                 control_frame = L2CAP_Control_Frame.from_bytes(l2cap_pdu.payload)
                 self.analyzer.emit(control_frame)

bumble/smp.py

@@ -155,6 +155,7 @@ SMP_CT2_AUTHREQ      = 0b00100000
 SMP_CTKD_H7_LEBR_SALT = bytes.fromhex('00000000000000000000000000000000746D7031')
 SMP_CTKD_H7_BRLE_SALT = bytes.fromhex('00000000000000000000000000000000746D7032')
 
+
 # -----------------------------------------------------------------------------
 # Utils
 # -----------------------------------------------------------------------------
@@ -879,7 +880,7 @@ class Session:
                 )
             )
         )
-    
+
     async def derive_ltk(self):
         link_key = await self.manager.device.get_link_key(self.connection.peer_address)
         assert link_key is not None
@@ -914,7 +915,7 @@ class Session:
             csrk = bytes(16)  # FIXME: testing
             if self.initiator_key_distribution & SMP_SIGN_KEY_DISTRIBUTION_FLAG:
                 self.send_command(SMP_Signing_Information_Command(signature_key=csrk))
-            
+
             # CTKD, calculate BR/EDR link key
             if self.initiator_key_distribution & SMP_LINK_KEY_DISTRIBUTION_FLAG:
                 ilk = crypto.h7(
@@ -946,7 +947,7 @@ class Session:
             csrk = bytes(16)  # FIXME: testing
             if self.responder_key_distribution & SMP_SIGN_KEY_DISTRIBUTION_FLAG:
                 self.send_command(SMP_Signing_Information_Command(signature_key=csrk))
-            
+
             # CTKD, calculate BR/EDR link key
             if self.responder_key_distribution & SMP_LINK_KEY_DISTRIBUTION_FLAG:
                 ilk = crypto.h7(
@@ -980,12 +981,7 @@ class Session:
             self.peer_expected_distributions.remove(command_class)
             logger.debug(f'remaining distributions: {[c.__name__ for c in self.peer_expected_distributions]}')
             if not self.peer_expected_distributions:
-                # The initiator can now send its keys
-                if self.is_initiator:
-                    self.distribute_keys()
-
-                # Nothing left to expect, we're done
-                asyncio.create_task(self.on_pairing())
+                self.on_peer_key_distribution_complete()
         else:
             logger.warn(color(f'!!! unexpected key distribution command: {command_class.__name__}', 'red'))
             self.send_pairing_failed(SMP_UNSPECIFIED_REASON_ERROR)
@@ -1006,12 +1002,23 @@ class Session:
         self.connection.remove_listener('connection_encryption_key_refresh', self.on_connection_encryption_key_refresh)
         self.manager.on_session_end(self)
 
+    def on_peer_key_distribution_complete(self):
+        # The initiator can now send its keys
+        if self.is_initiator:
+            self.distribute_keys()
+
+        asyncio.create_task(self.on_pairing())
+
     def on_connection_encryption_change(self):
         if self.connection.is_encrypted:
             if self.is_responder:
                 # The responder distributes its keys first, the initiator later
                 self.distribute_keys()
 
+            # If we're not expecting key distributions from the peer, we're done
+            if not self.peer_expected_distributions:
+                self.on_peer_key_distribution_complete()
+
     def on_connection_encryption_key_refresh(self):
         # Do as if the connection had just been encrypted
         self.on_connection_encryption_change()

tests/gatt_test.py

@@ -22,6 +22,7 @@ import struct
 import pytest
 
 from bumble.controller import Controller
+from bumble.gatt_client import CharacteristicProxy
 from bumble.link import LocalLink
 from bumble.device import Device, Peer
 from bumble.host import Host
@@ -53,29 +54,29 @@ def basic_check(x):
     parsed = ATT_PDU.from_bytes(pdu)
     x_str = str(x)
     parsed_str = str(parsed)
-    assert(x_str == parsed_str)
+    assert x_str == parsed_str
 
 
 # -----------------------------------------------------------------------------
 def test_UUID():
     u = UUID.from_16_bits(0x7788)
-    assert(str(u) == 'UUID-16:7788')
+    assert str(u) == 'UUID-16:7788'
     u = UUID.from_32_bits(0x11223344)
-    assert(str(u) == 'UUID-32:11223344')
+    assert str(u) == 'UUID-32:11223344'
     u = UUID('61A3512C-09BE-4DDC-A6A6-0B03667AAFC6')
-    assert(str(u) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6')
+    assert str(u) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6'
     v = UUID(str(u))
-    assert(str(v) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6')
+    assert str(v) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6'
     w = UUID.from_bytes(v.to_bytes())
-    assert(str(w) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6')
+    assert str(w) == '61A3512C-09BE-4DDC-A6A6-0B03667AAFC6'
 
     u1 = UUID.from_16_bits(0x1234)
     b1 = u1.to_bytes(force_128 = True)
     u2 = UUID.from_bytes(b1)
-    assert(u1 == u2)
+    assert u1 == u2
 
     u3 = UUID.from_16_bits(0x180a)
-    assert(str(u3) == 'UUID-16:180A (Device Information)')
+    assert str(u3) == 'UUID-16:180A (Device Information)'
 
 
 # -----------------------------------------------------------------------------
@@ -98,6 +99,122 @@ def test_ATT_Read_By_Group_Type_Request():
     basic_check(pdu)
 
 
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_characteristic_encoding():
+    class Foo(Characteristic):
+        def encode_value(self, value):
+            return bytes([value])
+
+        def decode_value(self, value_bytes):
+            return value_bytes[0]
+
+    c = Foo(GATT_BATTERY_LEVEL_CHARACTERISTIC, Characteristic.READ, Characteristic.READABLE, 123)
+    x = c.read_value(None)
+    assert x == bytes([123])
+    c.write_value(None, bytes([122]))
+    assert c.value == 122
+
+    class FooProxy(CharacteristicProxy):
+        def __init__(self, characteristic):
+            super().__init__(
+                characteristic.client,
+                characteristic.handle,
+                characteristic.end_group_handle,
+                characteristic.uuid,
+                characteristic.properties
+            )
+
+        def encode_value(self, value):
+            return bytes([value])
+
+        def decode_value(self, value_bytes):
+            return value_bytes[0]
+
+    [client, server] = TwoDevices().devices
+
+    characteristic = Characteristic(
+        'FDB159DB-036C-49E3-B3DB-6325AC750806',
+        Characteristic.READ | Characteristic.WRITE | Characteristic.NOTIFY,
+        Characteristic.READABLE | Characteristic.WRITEABLE,
+        bytes([123])
+    )
+
+    service = Service(
+        '3A657F47-D34F-46B3-B1EC-698E29B6B829',
+        [characteristic]
+    )
+    server.add_service(service)
+
+    await client.power_on()
+    await server.power_on()
+    connection = await client.connect(server.random_address)
+    peer = Peer(connection)
+
+    await peer.discover_services()
+    await peer.discover_characteristics()
+    c = peer.get_characteristics_by_uuid(characteristic.uuid)
+    assert len(c) == 1
+    c = c[0]
+    cp = FooProxy(c)
+
+    v = await cp.read_value()
+    assert v == 123
+    await cp.write_value(124)
+    await async_barrier()
+    assert characteristic.value == bytes([124])
+
+    last_change = None
+
+    def on_change(value):
+        nonlocal last_change
+        last_change = value
+
+    await c.subscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change == characteristic.value
+    last_change = None
+
+    await server.notify_subscribers(characteristic, value=bytes([125]))
+    await async_barrier()
+    assert last_change == bytes([125])
+    last_change = None
+
+    await c.unsubscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change is None
+
+    await cp.subscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change == characteristic.value[0]
+    last_change = None
+
+    await server.notify_subscribers(characteristic, value=bytes([126]))
+    await async_barrier()
+    assert last_change == 126
+    last_change = None
+
+    await cp.unsubscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change is None
+
+    cd = DelegatedCharacteristicAdapter(c, decode=lambda x: x[0])
+    await cd.subscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change == characteristic.value[0]
+    last_change = None
+
+    await cd.unsubscribe(on_change)
+    await server.notify_subscribers(characteristic)
+    await async_barrier()
+    assert last_change is None
+
+
 # -----------------------------------------------------------------------------
 def test_CharacteristicAdapter():
     # Check that the CharacteristicAdapter base class is transparent
@@ -106,21 +223,21 @@ def test_CharacteristicAdapter():
     a = CharacteristicAdapter(c)
 
     value = a.read_value(None)
-    assert(value == v)
+    assert value == v
 
     v = bytes([3, 4, 5])
     a.write_value(None, v)
-    assert(c.value == v)
+    assert c.value == v
 
     # Simple delegated adapter
     a = DelegatedCharacteristicAdapter(c, lambda x: bytes(reversed(x)), lambda x: bytes(reversed(x)))
 
     value = a.read_value(None)
-    assert(value == bytes(reversed(v)))
+    assert value == bytes(reversed(v))
 
     v = bytes([3, 4, 5])
     a.write_value(None, v)
-    assert(a.value == bytes(reversed(v)))
+    assert a.value == bytes(reversed(v))
 
     # Packed adapter with single element format
     v = 1234
@@ -129,10 +246,10 @@ def test_CharacteristicAdapter():
     a = PackedCharacteristicAdapter(c, '>H')
 
     value = a.read_value(None)
-    assert(value == pv)
+    assert value == pv
     c.value = None
     a.write_value(None, pv)
-    assert(a.value == v)
+    assert a.value == v
 
     # Packed adapter with multi-element format
     v1 = 1234
@@ -142,10 +259,10 @@ def test_CharacteristicAdapter():
     a = PackedCharacteristicAdapter(c, '>HH')
 
     value = a.read_value(None)
-    assert(value == pv)
+    assert value == pv
     c.value = None
     a.write_value(None, pv)
-    assert(a.value == (v1, v2))
+    assert a.value == (v1, v2)
 
     # Mapped adapter
     v1 = 1234
@@ -156,10 +273,10 @@ def test_CharacteristicAdapter():
     a = MappedCharacteristicAdapter(c, '>HH', ('v1', 'v2'))
 
     value = a.read_value(None)
-    assert(value == pv)
+    assert value == pv
     c.value = None
     a.write_value(None, pv)
-    assert(a.value == mapped)
+    assert a.value == mapped
 
     # UTF-8 adapter
     v = 'Hello π'
@@ -168,10 +285,10 @@ def test_CharacteristicAdapter():
     a = UTF8CharacteristicAdapter(c)
 
     value = a.read_value(None)
-    assert(value == ev)
+    assert value == ev
     c.value = None
     a.write_value(None, ev)
-    assert(a.value == v)
+    assert a.value == v
 
 
 # -----------------------------------------------------------------------------
@@ -179,13 +296,13 @@ def test_CharacteristicValue():
     b = bytes([1, 2, 3])
     c = CharacteristicValue(read=lambda _: b)
     x = c.read(None)
-    assert(x == b)
+    assert x == b
 
     result = []
     c = CharacteristicValue(write=lambda connection, value: result.append((connection, value)))
     z = object()
     c.write(z, b)
-    assert(result == [(z, b)])
+    assert result == [(z, b)]
 
 
 # -----------------------------------------------------------------------------
@@ -265,35 +382,35 @@ async def test_read_write():
     await peer.discover_services()
     await peer.discover_characteristics()
     c = peer.get_characteristics_by_uuid(characteristic1.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c1 = c[0]
     c = peer.get_characteristics_by_uuid(characteristic2.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c2 = c[0]
 
     v1 = await peer.read_value(c1)
-    assert(v1 == b'')
+    assert v1 == b''
     b = bytes([1, 2, 3])
     await peer.write_value(c1, b)
     await async_barrier()
-    assert(characteristic1.value == b)
+    assert characteristic1.value == b
     v1 = await peer.read_value(c1)
-    assert(v1 == b)
-    assert(type(characteristic1._last_value) is tuple)
-    assert(len(characteristic1._last_value) == 2)
-    assert(str(characteristic1._last_value[0].peer_address) == str(client.random_address))
-    assert(characteristic1._last_value[1] == b)
+    assert v1 == b
+    assert type(characteristic1._last_value is tuple)
+    assert len(characteristic1._last_value) == 2
+    assert str(characteristic1._last_value[0].peer_address) == str(client.random_address)
+    assert characteristic1._last_value[1] == b
     bb = bytes([3, 4, 5, 6])
     characteristic1.value = bb
     v1 = await peer.read_value(c1)
-    assert(v1 == bb)
+    assert v1 == bb
 
     await peer.write_value(c2, b)
     await async_barrier()
-    assert(type(characteristic2._last_value) is tuple)
-    assert(len(characteristic2._last_value) == 2)
-    assert(str(characteristic2._last_value[0].peer_address) == str(client.random_address))
-    assert(characteristic2._last_value[1] == b)
+    assert type(characteristic2._last_value is tuple)
+    assert len(characteristic2._last_value) == 2
+    assert str(characteristic2._last_value[0].peer_address) == str(client.random_address)
+    assert characteristic2._last_value[1] == b
 
 
 # -----------------------------------------------------------------------------
@@ -324,26 +441,26 @@ async def test_read_write2():
 
     await peer.discover_services()
     c = peer.get_services_by_uuid(service1.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     s = c[0]
     await s.discover_characteristics()
     c = s.get_characteristics_by_uuid(characteristic1.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c1 = c[0]
 
     v1 = await c1.read_value()
-    assert(v1 == v)
+    assert v1 == v
 
     a1 = PackedCharacteristicAdapter(c1, '>I')
     v1 = await a1.read_value()
-    assert(v1 == struct.unpack('>I', v)[0])
+    assert v1 == struct.unpack('>I', v)[0]
 
     b = bytes([0x55, 0x66, 0x77, 0x88])
     await a1.write_value(struct.unpack('>I', b)[0])
     await async_barrier()
-    assert(characteristic1.value == b)
+    assert characteristic1.value == b
     v1 = await a1.read_value()
-    assert(v1 == struct.unpack('>I', b)[0])
+    assert v1 == struct.unpack('>I', b)[0]
 
 
 # -----------------------------------------------------------------------------
@@ -410,13 +527,13 @@ async def test_subscribe_notify():
     await peer.discover_services()
     await peer.discover_characteristics()
     c = peer.get_characteristics_by_uuid(characteristic1.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c1 = c[0]
     c = peer.get_characteristics_by_uuid(characteristic2.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c2 = c[0]
     c = peer.get_characteristics_by_uuid(characteristic3.uuid)
-    assert(len(c) == 1)
+    assert len(c) == 1
     c3 = c[0]
 
     c1._called = False
@@ -429,23 +546,32 @@ async def test_subscribe_notify():
     c1.on('update', on_c1_update)
     await peer.subscribe(c1)
     await async_barrier()
-    assert(server._last_subscription[1] == characteristic1)
-    assert(server._last_subscription[2])
-    assert(not server._last_subscription[3])
-    assert(characteristic1._last_subscription[1])
-    assert(not characteristic1._last_subscription[2])
+    assert server._last_subscription[1] == characteristic1
+    assert server._last_subscription[2]
+    assert not server._last_subscription[3]
+    assert characteristic1._last_subscription[1]
+    assert not characteristic1._last_subscription[2]
     await server.indicate_subscribers(characteristic1)
     await async_barrier()
-    assert(not c1._called)
+    assert not c1._called
     await server.notify_subscribers(characteristic1)
     await async_barrier()
-    assert(c1._called)
-    assert(c1._last_update == characteristic1.value)
+    assert c1._called
+    assert c1._last_update == characteristic1.value
+
+    c1._called = False
+    c1._last_update = None
+    c1_value = characteristic1.value
+    await server.notify_subscribers(characteristic1, bytes([0, 1, 2]))
+    await async_barrier()
+    assert c1._called
+    assert c1._last_update == bytes([0, 1, 2])
+    assert characteristic1.value == c1_value
 
     c1._called = False
     await peer.unsubscribe(c1)
     await server.notify_subscribers(characteristic1)
-    assert(not c1._called)
+    assert not c1._called
 
     c2._called = False
     c2._last_update = None
@@ -458,17 +584,17 @@ async def test_subscribe_notify():
     await async_barrier()
     await server.notify_subscriber(characteristic2._last_subscription[0], characteristic2)
     await async_barrier()
-    assert(not c2._called)
+    assert not c2._called
     await server.indicate_subscriber(characteristic2._last_subscription[0], characteristic2)
     await async_barrier()
-    assert(c2._called)
-    assert(c2._last_update == characteristic2.value)
+    assert c2._called
+    assert c2._last_update == characteristic2.value
 
     c2._called = False
     await peer.unsubscribe(c2, on_c2_update)
     await server.indicate_subscriber(characteristic2._last_subscription[0], characteristic2)
     await async_barrier()
-    assert(not c2._called)
+    assert not c2._called
 
     def on_c3_update(value):
         c3._called = True
@@ -483,17 +609,17 @@ async def test_subscribe_notify():
     await async_barrier()
     await server.notify_subscriber(characteristic3._last_subscription[0], characteristic3)
     await async_barrier()
-    assert(c3._called)
-    assert(c3._last_update == characteristic3.value)
-    assert(c3._called_2)
-    assert(c3._last_update_2 == characteristic3.value)
+    assert c3._called
+    assert c3._last_update == characteristic3.value
+    assert c3._called_2
+    assert c3._last_update_2 == characteristic3.value
     characteristic3.value = bytes([1, 2, 3])
     await server.indicate_subscriber(characteristic3._last_subscription[0], characteristic3)
     await async_barrier()
-    assert(c3._called)
-    assert(c3._last_update == characteristic3.value)
-    assert(c3._called_2)
-    assert(c3._last_update_2 == characteristic3.value)
+    assert c3._called
+    assert c3._last_update == characteristic3.value
+    assert c3._called_2
+    assert c3._last_update_2 == characteristic3.value
 
     c3._called = False
     c3._called_2 = False
@@ -501,8 +627,8 @@ async def test_subscribe_notify():
     await server.notify_subscriber(characteristic3._last_subscription[0], characteristic3)
     await server.indicate_subscriber(characteristic3._last_subscription[0], characteristic3)
     await async_barrier()
-    assert(not c3._called)
-    assert(not c3._called_2)
+    assert not c3._called
+    assert not c3._called_2
 
 
 # -----------------------------------------------------------------------------
@@ -510,6 +636,8 @@ async def async_main():
     await test_read_write()
     await test_read_write2()
     await test_subscribe_notify()
+    await test_characteristic_encoding()
+
 
 # -----------------------------------------------------------------------------
 if __name__ == '__main__':

tests/self_test.py

@@ -246,8 +246,7 @@ IO_CAP = [
 SC = [False, True]
 MITM = [False, True]
 # Key distribution is a 4-bit bitmask
-# IdKey is necessary for current SMP structure
-KEY_DIST = [i for i in range(16) if (i & SMP_ID_KEY_DISTRIBUTION_FLAG)]
+KEY_DIST = range(16)
 
 @pytest.mark.asyncio
 @pytest.mark.parametrize('io_cap, sc, mitm, key_dist',