use TCP_NODELAY on socket

Co-authored-by: zxzxwu <92432172+zxzxwu@users.noreply.github.com>

apps/bench.py

@@ -82,10 +82,11 @@ SPEED_RX_UUID = '016A2CC7-E14B-4819-935F-1F56EAE4098D'
 DEFAULT_RFCOMM_UUID = 'E6D55659-C8B4-4B85-96BB-B1143AF6D3AE'
 DEFAULT_L2CAP_PSM = 1234
 DEFAULT_L2CAP_MAX_CREDITS = 128
-DEFAULT_L2CAP_MTU = 1022
-DEFAULT_L2CAP_MPS = 1024
+DEFAULT_L2CAP_MTU = 1024
+DEFAULT_L2CAP_MPS = 1022
 
 DEFAULT_LINGER_TIME = 1.0
+DEFAULT_POST_CONNECTION_WAIT_TIME = 1.0
 
 DEFAULT_RFCOMM_CHANNEL = 8
 
@@ -952,6 +953,10 @@ class Central(Connection.Listener):
 
             await self.device.power_on()
 
+            if self.classic:
+                await self.device.set_discoverable(False)
+                await self.device.set_connectable(False)
+
             print(color(f'### Connecting to {self.peripheral_address}...', 'cyan'))
             try:
                 self.connection = await self.device.connect(
@@ -972,6 +977,11 @@ class Central(Connection.Listener):
             self.connection.listener = self
             print_connection(self.connection)
 
+            # Wait a bit after the connection, some controllers aren't very good when
+            # we start sending data right away while some connection parameters are
+            # updated post connection
+            await asyncio.sleep(DEFAULT_POST_CONNECTION_WAIT_TIME)
+
             # Request a new data length if requested
             if self.extended_data_length:
                 print(color('+++ Requesting extended data length', 'cyan'))
@@ -1098,6 +1108,15 @@ class Peripheral(Device.Listener, Connection.Listener):
         self.connection = connection
         self.connected.set()
 
+        # Stop being discoverable and connectable
+        if self.classic:
+
+            async def stop_being_discoverable_connectable():
+                await self.device.set_discoverable(False)
+                await self.device.set_connectable(False)
+
+            AsyncRunner.spawn(stop_being_discoverable_connectable())
+
         # Request a new data length if needed
         if self.extended_data_length:
             print("+++ Requesting extended data length")

apps/controller_info.py

@@ -32,10 +32,14 @@ from bumble.hci import (
     HCI_Command,
     HCI_Command_Complete_Event,
     HCI_Command_Status_Event,
+    HCI_READ_BUFFER_SIZE_COMMAND,
+    HCI_Read_Buffer_Size_Command,
     HCI_READ_BD_ADDR_COMMAND,
     HCI_Read_BD_ADDR_Command,
     HCI_READ_LOCAL_NAME_COMMAND,
     HCI_Read_Local_Name_Command,
+    HCI_LE_READ_BUFFER_SIZE_COMMAND,
+    HCI_LE_Read_Buffer_Size_Command,
     HCI_LE_READ_MAXIMUM_DATA_LENGTH_COMMAND,
     HCI_LE_Read_Maximum_Data_Length_Command,
     HCI_LE_READ_NUMBER_OF_SUPPORTED_ADVERTISING_SETS_COMMAND,
@@ -59,7 +63,7 @@ def command_succeeded(response):
 
 
 # -----------------------------------------------------------------------------
-async def get_classic_info(host):
+async def get_classic_info(host: Host) -> None:
     if host.supports_command(HCI_READ_BD_ADDR_COMMAND):
         response = await host.send_command(HCI_Read_BD_ADDR_Command())
         if command_succeeded(response):
@@ -80,7 +84,7 @@ async def get_classic_info(host):
 
 
 # -----------------------------------------------------------------------------
-async def get_le_info(host):
+async def get_le_info(host: Host) -> None:
     print()
 
     if host.supports_command(HCI_LE_READ_NUMBER_OF_SUPPORTED_ADVERTISING_SETS_COMMAND):
@@ -136,6 +140,31 @@ async def get_le_info(host):
         print('  ', name_or_number(HCI_LE_SUPPORTED_FEATURES_NAMES, feature))
 
 
+# -----------------------------------------------------------------------------
+async def get_acl_flow_control_info(host: Host) -> None:
+    print()
+
+    if host.supports_command(HCI_READ_BUFFER_SIZE_COMMAND):
+        response = await host.send_command(
+            HCI_Read_Buffer_Size_Command(), check_result=True
+        )
+        print(
+            color('ACL Flow Control:', 'yellow'),
+            f'{response.return_parameters.hc_total_num_acl_data_packets} '
+            f'packets of size {response.return_parameters.hc_acl_data_packet_length}',
+        )
+
+    if host.supports_command(HCI_LE_READ_BUFFER_SIZE_COMMAND):
+        response = await host.send_command(
+            HCI_LE_Read_Buffer_Size_Command(), check_result=True
+        )
+        print(
+            color('LE ACL Flow Control:', 'yellow'),
+            f'{response.return_parameters.hc_total_num_le_acl_data_packets} '
+            f'packets of size {response.return_parameters.hc_le_acl_data_packet_length}',
+        )
+
+
 # -----------------------------------------------------------------------------
 async def async_main(transport):
     print('<<< connecting to HCI...')
@@ -168,6 +197,9 @@ async def async_main(transport):
         # Get the LE info
         await get_le_info(host)
 
+        # Print the ACL flow control info
+        await get_acl_flow_control_info(host)
+
         # Print the list of commands supported by the controller
         print()
         print(color('Supported Commands:', 'yellow'))

bumble/controller.py

@@ -134,12 +134,14 @@ class Controller:
             '0000000060000000'
         )  # BR/EDR Not Supported, LE Supported (Controller)
         self.manufacturer_name = 0xFFFF
+        self.hc_data_packet_length = 27
+        self.hc_total_num_data_packets = 64
         self.hc_le_data_packet_length = 27
         self.hc_total_num_le_data_packets = 64
         self.event_mask = 0
         self.event_mask_page_2 = 0
         self.supported_commands = bytes.fromhex(
-            '2000800000c000000000e40000002822000000000000040000f7ffff7f000000'
+            '2000800000c000000000e4000000a822000000000000040000f7ffff7f000000'
             '30f0f9ff01008004000000000000000000000000000000000000000000000000'
         )
         self.le_event_mask = 0
@@ -914,6 +916,19 @@ class Controller:
         '''
         return bytes([HCI_SUCCESS]) + self.lmp_features
 
+    def on_hci_read_buffer_size_command(self, _command):
+        '''
+        See Bluetooth spec Vol 4, Part E - 7.4.5 Read Buffer Size Command
+        '''
+        return struct.pack(
+            '<BHBHH',
+            HCI_SUCCESS,
+            self.hc_data_packet_length,
+            0,
+            self.hc_total_num_data_packets,
+            0,
+        )
+
     def on_hci_read_bd_addr_command(self, _command):
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.6 Read BD_ADDR Command

bumble/host.py

@@ -21,7 +21,7 @@ import collections
 import logging
 import struct
 
-from typing import Any, Awaitable, Callable, Dict, Optional, Union, cast, TYPE_CHECKING
+from typing import Any, Awaitable, Callable, Deque, Dict, Optional, cast, TYPE_CHECKING
 
 from bumble.colors import color
 from bumble.l2cap import L2CAP_PDU
@@ -91,16 +91,49 @@ logger = logging.getLogger(__name__)
 
 
 # -----------------------------------------------------------------------------
-# Constants
-# -----------------------------------------------------------------------------
-# fmt: off
+class AclPacketQueue:
+    max_packet_size: int
 
-HOST_DEFAULT_HC_LE_ACL_DATA_PACKET_LENGTH = 27
-HOST_HC_TOTAL_NUM_LE_ACL_DATA_PACKETS     = 1
-HOST_DEFAULT_HC_ACL_DATA_PACKET_LENGTH    = 27
-HOST_HC_TOTAL_NUM_ACL_DATA_PACKETS        = 1
+    def __init__(
+        self,
+        max_packet_size: int,
+        max_in_flight: int,
+        send: Callable[[HCI_Packet], None],
+    ) -> None:
+        self.max_packet_size = max_packet_size
+        self.max_in_flight = max_in_flight
+        self.in_flight = 0
+        self.send = send
+        self.packets: Deque[HCI_AclDataPacket] = collections.deque()
 
-# fmt: on
+    def enqueue(self, packet: HCI_AclDataPacket) -> None:
+        self.packets.appendleft(packet)
+        self.check_queue()
+
+        if self.packets:
+            logger.debug(
+                f'{self.in_flight} ACL packets in flight, '
+                f'{len(self.packets)} in queue'
+            )
+
+    def check_queue(self) -> None:
+        while self.packets and self.in_flight < self.max_in_flight:
+            packet = self.packets.pop()
+            self.send(packet)
+            self.in_flight += 1
+
+    def on_packets_completed(self, packet_count: int) -> None:
+        if packet_count > self.in_flight:
+            logger.warning(
+                color(
+                    '!!! {packet_count} completed but only '
+                    f'{self.in_flight} in flight'
+                )
+            )
+            packet_count = self.in_flight
+
+        self.in_flight -= packet_count
+        self.check_queue()
 
 
 # -----------------------------------------------------------------------------
@@ -111,6 +144,13 @@ class Connection:
         self.peer_address = peer_address
         self.assembler = HCI_AclDataPacketAssembler(self.on_acl_pdu)
         self.transport = transport
+        acl_packet_queue: Optional[AclPacketQueue] = (
+            host.le_acl_packet_queue
+            if transport == BT_LE_TRANSPORT
+            else host.acl_packet_queue
+        )
+        assert acl_packet_queue
+        self.acl_packet_queue = acl_packet_queue
 
     def on_hci_acl_data_packet(self, packet: HCI_AclDataPacket) -> None:
         self.assembler.feed_packet(packet)
@@ -123,7 +163,8 @@ class Connection:
 # -----------------------------------------------------------------------------
 class Host(AbortableEventEmitter):
     connections: Dict[int, Connection]
-    acl_packet_queue: collections.deque[HCI_AclDataPacket]
+    acl_packet_queue: Optional[AclPacketQueue] = None
+    le_acl_packet_queue: Optional[AclPacketQueue] = None
     hci_sink: Optional[TransportSink] = None
     hci_metadata: Dict[str, Any]
     long_term_key_provider: Optional[
@@ -143,12 +184,6 @@ class Host(AbortableEventEmitter):
         self.connections = {}  # Connections, by connection handle
         self.pending_command = None
         self.pending_response = None
-        self.hc_le_acl_data_packet_length = HOST_DEFAULT_HC_LE_ACL_DATA_PACKET_LENGTH
-        self.hc_total_num_le_acl_data_packets = HOST_HC_TOTAL_NUM_LE_ACL_DATA_PACKETS
-        self.hc_acl_data_packet_length = HOST_DEFAULT_HC_ACL_DATA_PACKET_LENGTH
-        self.hc_total_num_acl_data_packets = HOST_HC_TOTAL_NUM_ACL_DATA_PACKETS
-        self.acl_packet_queue = collections.deque()
-        self.acl_packets_in_flight = 0
         self.local_version = None
         self.local_supported_commands = bytes(64)
         self.local_le_features = 0
@@ -254,46 +289,54 @@ class Host(AbortableEventEmitter):
             response = await self.send_command(
                 HCI_Read_Buffer_Size_Command(), check_result=True
             )
-            self.hc_acl_data_packet_length = (
+            hc_acl_data_packet_length = (
                 response.return_parameters.hc_acl_data_packet_length
             )
-            self.hc_total_num_acl_data_packets = (
+            hc_total_num_acl_data_packets = (
                 response.return_parameters.hc_total_num_acl_data_packets
             )
 
             logger.debug(
                 'HCI ACL flow control: '
-                f'hc_acl_data_packet_length={self.hc_acl_data_packet_length},'
-                f'hc_total_num_acl_data_packets={self.hc_total_num_acl_data_packets}'
+                f'hc_acl_data_packet_length={hc_acl_data_packet_length},'
+                f'hc_total_num_acl_data_packets={hc_total_num_acl_data_packets}'
             )
 
+            self.acl_packet_queue = AclPacketQueue(
+                max_packet_size=hc_acl_data_packet_length,
+                max_in_flight=hc_total_num_acl_data_packets,
+                send=self.send_hci_packet,
+            )
+
+        hc_le_acl_data_packet_length = 0
+        hc_total_num_le_acl_data_packets = 0
         if self.supports_command(HCI_LE_READ_BUFFER_SIZE_COMMAND):
             response = await self.send_command(
                 HCI_LE_Read_Buffer_Size_Command(), check_result=True
             )
-            self.hc_le_acl_data_packet_length = (
+            hc_le_acl_data_packet_length = (
                 response.return_parameters.hc_le_acl_data_packet_length
             )
-            self.hc_total_num_le_acl_data_packets = (
+            hc_total_num_le_acl_data_packets = (
                 response.return_parameters.hc_total_num_le_acl_data_packets
             )
 
             logger.debug(
                 'HCI LE ACL flow control: '
-                f'hc_le_acl_data_packet_length={self.hc_le_acl_data_packet_length},'
-                'hc_total_num_le_acl_data_packets='
-                f'{self.hc_total_num_le_acl_data_packets}'
+                f'hc_le_acl_data_packet_length={hc_le_acl_data_packet_length},'
+                f'hc_total_num_le_acl_data_packets={hc_total_num_le_acl_data_packets}'
             )
 
-            if (
-                response.return_parameters.hc_le_acl_data_packet_length == 0
-                or response.return_parameters.hc_total_num_le_acl_data_packets == 0
-            ):
-                # LE and Classic share the same values
-                self.hc_le_acl_data_packet_length = self.hc_acl_data_packet_length
-                self.hc_total_num_le_acl_data_packets = (
-                    self.hc_total_num_acl_data_packets
-                )
+        if hc_le_acl_data_packet_length == 0 or hc_total_num_le_acl_data_packets == 0:
+            # LE and Classic share the same queue
+            self.le_acl_packet_queue = self.acl_packet_queue
+        else:
+            # Create a separate queue for LE
+            self.le_acl_packet_queue = AclPacketQueue(
+                max_packet_size=hc_le_acl_data_packet_length,
+                max_in_flight=hc_total_num_le_acl_data_packets,
+                send=self.send_hci_packet,
+            )
 
         if self.supports_command(
             HCI_LE_READ_SUGGESTED_DEFAULT_DATA_LENGTH_COMMAND
@@ -332,14 +375,13 @@ class Host(AbortableEventEmitter):
         self.hci_metadata = getattr(source, 'metadata', self.hci_metadata)
 
     def send_hci_packet(self, packet: HCI_Packet) -> None:
+        logger.debug(f'{color("### HOST -> CONTROLLER", "blue")}: {packet}')
         if self.snooper:
             self.snooper.snoop(bytes(packet), Snooper.Direction.HOST_TO_CONTROLLER)
         if self.hci_sink:
             self.hci_sink.on_packet(bytes(packet))
 
     async def send_command(self, command, check_result=False):
-        logger.debug(f'{color("### HOST -> CONTROLLER", "blue")}: {command}')
-
         # Wait until we can send (only one pending command at a time)
         async with self.command_semaphore:
             assert self.pending_command is None
@@ -387,6 +429,17 @@ class Host(AbortableEventEmitter):
         asyncio.create_task(send_command(command))
 
     def send_l2cap_pdu(self, connection_handle: int, cid: int, pdu: bytes) -> None:
+        if not (connection := self.connections.get(connection_handle)):
+            logger.warning(f'connection 0x{connection_handle:04X} not found')
+            return
+        packet_queue = connection.acl_packet_queue
+        if packet_queue is None:
+            logger.warning(
+                f'no ACL packet queue for connection 0x{connection_handle:04X}'
+            )
+            return
+
+        # Create a PDU
         l2cap_pdu = bytes(L2CAP_PDU(cid, pdu))
 
         # Send the data to the controller via ACL packets
@@ -394,8 +447,7 @@ class Host(AbortableEventEmitter):
         offset = 0
         pb_flag = 0
         while bytes_remaining:
-            # TODO: support different LE/Classic lengths
-            data_total_length = min(bytes_remaining, self.hc_le_acl_data_packet_length)
+            data_total_length = min(bytes_remaining, packet_queue.max_packet_size)
             acl_packet = HCI_AclDataPacket(
                 connection_handle=connection_handle,
                 pb_flag=pb_flag,
@@ -403,34 +455,12 @@ class Host(AbortableEventEmitter):
                 data_total_length=data_total_length,
                 data=l2cap_pdu[offset : offset + data_total_length],
             )
-            logger.debug(
-                f'{color("### HOST -> CONTROLLER", "blue")}: (CID={cid}) {acl_packet}'
-            )
-            self.queue_acl_packet(acl_packet)
+            logger.debug(f'>>> ACL packet enqueue: (CID={cid}) {acl_packet}')
+            packet_queue.enqueue(acl_packet)
             pb_flag = 1
             offset += data_total_length
             bytes_remaining -= data_total_length
 
-    def queue_acl_packet(self, acl_packet: HCI_AclDataPacket) -> None:
-        self.acl_packet_queue.appendleft(acl_packet)
-        self.check_acl_packet_queue()
-
-        if len(self.acl_packet_queue):
-            logger.debug(
-                f'{self.acl_packets_in_flight} ACL packets in flight, '
-                f'{len(self.acl_packet_queue)} in queue'
-            )
-
-    def check_acl_packet_queue(self) -> None:
-        # Send all we can (TODO: support different LE/Classic limits)
-        while (
-            len(self.acl_packet_queue) > 0
-            and self.acl_packets_in_flight < self.hc_total_num_le_acl_data_packets
-        ):
-            packet = self.acl_packet_queue.pop()
-            self.send_hci_packet(packet)
-            self.acl_packets_in_flight += 1
-
     def supports_command(self, command):
         # Find the support flag position for this command
         for octet, flags in enumerate(HCI_SUPPORTED_COMMANDS_FLAGS):
@@ -553,7 +583,7 @@ class Host(AbortableEventEmitter):
             # This is used just for the Num_HCI_Command_Packets field, not related to
             # an actual command
             logger.debug('no-command event')
-            return None
+            return
 
         return self.on_command_processed(event)
 
@@ -561,18 +591,17 @@ class Host(AbortableEventEmitter):
         return self.on_command_processed(event)
 
     def on_hci_number_of_completed_packets_event(self, event):
-        total_packets = sum(event.num_completed_packets)
-        if total_packets <= self.acl_packets_in_flight:
-            self.acl_packets_in_flight -= total_packets
-            self.check_acl_packet_queue()
-        else:
-            logger.warning(
-                color(
-                    '!!! {total_packets} completed but only '
-                    f'{self.acl_packets_in_flight} in flight'
+        for connection_handle, num_completed_packets in zip(
+            event.connection_handles, event.num_completed_packets
+        ):
+            if not (connection := self.connections.get(connection_handle)):
+                logger.warning(
+                    'received packet completion event for unknown handle '
+                    f'0x{connection_handle:04X}'
                 )
-            )
-            self.acl_packets_in_flight = 0
+                continue
+
+            connection.acl_packet_queue.on_packets_completed(num_completed_packets)
 
     # Classic only
     def on_hci_connection_request_event(self, event):

bumble/l2cap.py

@@ -151,8 +151,8 @@ L2CAP_LE_CREDIT_BASED_CONNECTION_MAX_CREDITS             = 65535
 L2CAP_LE_CREDIT_BASED_CONNECTION_MIN_MTU                 = 23
 L2CAP_LE_CREDIT_BASED_CONNECTION_MIN_MPS                 = 23
 L2CAP_LE_CREDIT_BASED_CONNECTION_MAX_MPS                 = 65533
-L2CAP_LE_CREDIT_BASED_CONNECTION_DEFAULT_MTU             = 2046
-L2CAP_LE_CREDIT_BASED_CONNECTION_DEFAULT_MPS             = 2048
+L2CAP_LE_CREDIT_BASED_CONNECTION_DEFAULT_MTU             = 2048
+L2CAP_LE_CREDIT_BASED_CONNECTION_DEFAULT_MPS             = 2046
 L2CAP_LE_CREDIT_BASED_CONNECTION_DEFAULT_INITIAL_CREDITS = 256
 
 L2CAP_MAXIMUM_TRANSMISSION_UNIT_CONFIGURATION_OPTION_TYPE = 0x01

bumble/rfcomm.py

@@ -118,8 +118,8 @@ CRC_TABLE = bytes([
     0XBA, 0X2B, 0X59, 0XC8, 0XBD, 0X2C, 0X5E, 0XCF
 ])
 
-RFCOMM_DEFAULT_INITIAL_RX_CREDITS = 7
-RFCOMM_DEFAULT_PREFERRED_MTU      = 1280
+RFCOMM_DEFAULT_WINDOW_SIZE    = 16
+RFCOMM_DEFAULT_MAX_FRAME_SIZE = 2000
 
 RFCOMM_DYNAMIC_CHANNEL_NUMBER_START = 1
 RFCOMM_DYNAMIC_CHANNEL_NUMBER_END   = 30
@@ -438,14 +438,16 @@ class DLC(EventEmitter):
         multiplexer: Multiplexer,
         dlci: int,
         max_frame_size: int,
-        initial_tx_credits: int,
+        window_size: int,
     ) -> None:
         super().__init__()
         self.multiplexer = multiplexer
         self.dlci = dlci
-        self.rx_credits = RFCOMM_DEFAULT_INITIAL_RX_CREDITS
-        self.rx_threshold = self.rx_credits // 2
-        self.tx_credits = initial_tx_credits
+        self.max_frame_size = max_frame_size
+        self.window_size = window_size
+        self.rx_credits = window_size
+        self.rx_threshold = window_size // 2
+        self.tx_credits = window_size
         self.tx_buffer = b''
         self.state = DLC.State.INIT
         self.role = multiplexer.role
@@ -537,11 +539,11 @@ class DLC(EventEmitter):
         if len(data) and self.sink:
             self.sink(data)  # pylint: disable=not-callable
 
-        # Update the credits
-        if self.rx_credits > 0:
-            self.rx_credits -= 1
-        else:
-            logger.warning(color('!!! received frame with no rx credits', 'red'))
+            # Update the credits
+            if self.rx_credits > 0:
+                self.rx_credits -= 1
+            else:
+                logger.warning(color('!!! received frame with no rx credits', 'red'))
 
         # Check if there's anything to send (including credits)
         self.process_tx()
@@ -580,9 +582,9 @@ class DLC(EventEmitter):
             cl=0xE0,
             priority=7,
             ack_timer=0,
-            max_frame_size=RFCOMM_DEFAULT_PREFERRED_MTU,
+            max_frame_size=self.max_frame_size,
             max_retransmissions=0,
-            window_size=RFCOMM_DEFAULT_INITIAL_RX_CREDITS,
+            window_size=self.window_size,
         )
         mcc = RFCOMM_Frame.make_mcc(mcc_type=RFCOMM_MCC_PN_TYPE, c_r=0, data=bytes(pn))
         logger.debug(f'>>> PN Response: {pn}')
@@ -591,7 +593,7 @@ class DLC(EventEmitter):
 
     def rx_credits_needed(self) -> int:
         if self.rx_credits <= self.rx_threshold:
-            return RFCOMM_DEFAULT_INITIAL_RX_CREDITS - self.rx_credits
+            return self.window_size - self.rx_credits
 
         return 0
 
@@ -843,7 +845,12 @@ class Multiplexer(EventEmitter):
         )
         await self.disconnection_result
 
-    async def open_dlc(self, channel: int) -> DLC:
+    async def open_dlc(
+        self,
+        channel: int,
+        max_frame_size: int = RFCOMM_DEFAULT_MAX_FRAME_SIZE,
+        window_size: int = RFCOMM_DEFAULT_WINDOW_SIZE,
+    ) -> DLC:
         if self.state != Multiplexer.State.CONNECTED:
             if self.state == Multiplexer.State.OPENING:
                 raise InvalidStateError('open already in progress')
@@ -855,9 +862,9 @@ class Multiplexer(EventEmitter):
             cl=0xF0,
             priority=7,
             ack_timer=0,
-            max_frame_size=RFCOMM_DEFAULT_PREFERRED_MTU,
+            max_frame_size=max_frame_size,
             max_retransmissions=0,
-            window_size=RFCOMM_DEFAULT_INITIAL_RX_CREDITS,
+            window_size=window_size,
         )
         mcc = RFCOMM_Frame.make_mcc(mcc_type=RFCOMM_MCC_PN_TYPE, c_r=1, data=bytes(pn))
         logger.debug(f'>>> Sending MCC: {pn}')

bumble/transport/usb.py

@@ -108,7 +108,7 @@ async def open_usb_transport(spec: str) -> Transport:
         USB_DEVICE_PROTOCOL_BLUETOOTH_PRIMARY_CONTROLLER,
     )
 
-    READ_SIZE = 1024
+    READ_SIZE = 4096
 
     class UsbPacketSink:
         def __init__(self, device, acl_out):

extras/android/RemoteHCI/app/src/main/java/com/github/google/bumble/remotehci/HciServer.java

@@ -42,6 +42,7 @@ public class HciServer {
         try (ServerSocket serverSocket = new ServerSocket(mPort)) {
             mListener.onMessage("Waiting for connection on port " + serverSocket.getLocalPort());
             try (Socket clientSocket = serverSocket.accept()) {
+                clientSocket.setTcpNoDelay(true);
                 mListener.onHostConnectionState(true);
                 mListener.onMessage("Connected");
                 HciParser parser = new HciParser(mListener);

tests/device_test.py

@@ -29,7 +29,7 @@ from bumble.core import (
     ConnectionParameters,
 )
 from bumble.device import Connection, Device
-from bumble.host import Host
+from bumble.host import AclPacketQueue, Host
 from bumble.hci import (
     HCI_ACCEPT_CONNECTION_REQUEST_COMMAND,
     HCI_COMMAND_STATUS_PENDING,
@@ -73,6 +73,13 @@ async def test_device_connect_parallel():
     d1 = Device(host=Host(None, None))
     d2 = Device(host=Host(None, None))
 
+    def _send(packet):
+        pass
+
+    d0.host.acl_packet_queue = AclPacketQueue(0, 0, _send)
+    d1.host.acl_packet_queue = AclPacketQueue(0, 0, _send)
+    d2.host.acl_packet_queue = AclPacketQueue(0, 0, _send)
+
     # enable classic
     d0.classic_enabled = True
     d1.classic_enabled = True