Merge pull request #499 from google/gbg/rfcomm-bridge

rfcomm bridge app

apps/bench.py

@@ -899,14 +899,26 @@ class L2capServer(StreamedPacketIO):
 # RfcommClient
 # -----------------------------------------------------------------------------
 class RfcommClient(StreamedPacketIO):
-    def __init__(self, device, channel, uuid, l2cap_mtu, max_frame_size, window_size):
+    def __init__(
+        self,
+        device,
+        channel,
+        uuid,
+        l2cap_mtu,
+        max_frame_size,
+        initial_credits,
+        max_credits,
+        credits_threshold,
+    ):
         super().__init__()
         self.device = device
         self.channel = channel
         self.uuid = uuid
         self.l2cap_mtu = l2cap_mtu
         self.max_frame_size = max_frame_size
-        self.window_size = window_size
+        self.initial_credits = initial_credits
+        self.max_credits = max_credits
+        self.credits_threshold = credits_threshold
         self.rfcomm_session = None
         self.ready = asyncio.Event()
 
@@ -940,12 +952,17 @@ class RfcommClient(StreamedPacketIO):
         logging.info(color(f'### Opening session for channel {channel}...', 'yellow'))
         try:
             dlc_options = {}
-            if self.max_frame_size:
+            if self.max_frame_size is not None:
                 dlc_options['max_frame_size'] = self.max_frame_size
-            if self.window_size:
+            if self.initial_credits is not None:
-                dlc_options['window_size'] = self.window_size
+                dlc_options['initial_credits'] = self.initial_credits
             rfcomm_session = await rfcomm_mux.open_dlc(channel, **dlc_options)
             logging.info(color(f'### Session open: {rfcomm_session}', 'yellow'))
+            if self.max_credits is not None:
+                rfcomm_session.rx_max_credits = self.max_credits
+            if self.credits_threshold is not None:
+                rfcomm_session.rx_credits_threshold = self.credits_threshold
+
         except bumble.core.ConnectionError as error:
             logging.info(color(f'!!! Session open failed: {error}', 'red'))
             await rfcomm_mux.disconnect()
@@ -969,8 +986,19 @@ class RfcommClient(StreamedPacketIO):
 # RfcommServer
 # -----------------------------------------------------------------------------
 class RfcommServer(StreamedPacketIO):
-    def __init__(self, device, channel, l2cap_mtu):
+    def __init__(
+        self,
+        device,
+        channel,
+        l2cap_mtu,
+        max_frame_size,
+        initial_credits,
+        max_credits,
+        credits_threshold,
+    ):
         super().__init__()
+        self.max_credits = max_credits
+        self.credits_threshold = credits_threshold
         self.dlc = None
         self.ready = asyncio.Event()
 
@@ -981,7 +1009,12 @@ class RfcommServer(StreamedPacketIO):
         rfcomm_server = bumble.rfcomm.Server(device, **server_options)
 
         # Listen for incoming DLC connections
-        channel_number = rfcomm_server.listen(self.on_dlc, channel)
+        dlc_options = {}
+        if max_frame_size is not None:
+            dlc_options['max_frame_size'] = max_frame_size
+        if initial_credits is not None:
+            dlc_options['initial_credits'] = initial_credits
+        channel_number = rfcomm_server.listen(self.on_dlc, channel, **dlc_options)
 
         # Setup the SDP to advertise this channel
         device.sdp_service_records = make_sdp_records(channel_number)
@@ -1004,6 +1037,10 @@ class RfcommServer(StreamedPacketIO):
         dlc.sink = self.on_packet
         self.io_sink = dlc.write
         self.dlc = dlc
+        if self.max_credits is not None:
+            dlc.rx_max_credits = self.max_credits
+        if self.credits_threshold is not None:
+            dlc.rx_credits_threshold = self.credits_threshold
 
     async def drain(self):
         assert self.dlc
@@ -1321,7 +1358,9 @@ def create_mode_factory(ctx, default_mode):
                 uuid=ctx.obj['rfcomm_uuid'],
                 l2cap_mtu=ctx.obj['rfcomm_l2cap_mtu'],
                 max_frame_size=ctx.obj['rfcomm_max_frame_size'],
-                window_size=ctx.obj['rfcomm_window_size'],
+                initial_credits=ctx.obj['rfcomm_initial_credits'],
+                max_credits=ctx.obj['rfcomm_max_credits'],
+                credits_threshold=ctx.obj['rfcomm_credits_threshold'],
             )
 
         if mode == 'rfcomm-server':
@@ -1329,6 +1368,10 @@ def create_mode_factory(ctx, default_mode):
                 device,
                 channel=ctx.obj['rfcomm_channel'],
                 l2cap_mtu=ctx.obj['rfcomm_l2cap_mtu'],
+                max_frame_size=ctx.obj['rfcomm_max_frame_size'],
+                initial_credits=ctx.obj['rfcomm_initial_credits'],
+                max_credits=ctx.obj['rfcomm_max_credits'],
+                credits_threshold=ctx.obj['rfcomm_credits_threshold'],
             )
 
         raise ValueError('invalid mode')
@@ -1427,9 +1470,19 @@ def create_role_factory(ctx, default_role):
     help='RFComm maximum frame size',
 )
 @click.option(
-    '--rfcomm-window-size',
+    '--rfcomm-initial-credits',
     type=int,
-    help='RFComm window size',
+    help='RFComm initial credits',
+)
+@click.option(
+    '--rfcomm-max-credits',
+    type=int,
+    help='RFComm max credits',
+)
+@click.option(
+    '--rfcomm-credits-threshold',
+    type=int,
+    help='RFComm credits threshold',
 )
 @click.option(
     '--l2cap-psm',
@@ -1530,7 +1583,9 @@ def bench(
     rfcomm_uuid,
     rfcomm_l2cap_mtu,
     rfcomm_max_frame_size,
-    rfcomm_window_size,
+    rfcomm_initial_credits,
+    rfcomm_max_credits,
+    rfcomm_credits_threshold,
     l2cap_psm,
     l2cap_mtu,
     l2cap_mps,
@@ -1545,7 +1600,9 @@ def bench(
     ctx.obj['rfcomm_uuid'] = rfcomm_uuid
     ctx.obj['rfcomm_l2cap_mtu'] = rfcomm_l2cap_mtu
     ctx.obj['rfcomm_max_frame_size'] = rfcomm_max_frame_size
-    ctx.obj['rfcomm_window_size'] = rfcomm_window_size
+    ctx.obj['rfcomm_initial_credits'] = rfcomm_initial_credits
+    ctx.obj['rfcomm_max_credits'] = rfcomm_max_credits
+    ctx.obj['rfcomm_credits_threshold'] = rfcomm_credits_threshold
     ctx.obj['l2cap_psm'] = l2cap_psm
     ctx.obj['l2cap_mtu'] = l2cap_mtu
     ctx.obj['l2cap_mps'] = l2cap_mps

apps/rfcomm_bridge.py

@@ -0,0 +1,511 @@
+# Copyright 2024 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.
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import asyncio
+import logging
+import os
+import time
+from typing import Optional
+
+import click
+
+from bumble.colors import color
+from bumble.device import Device, DeviceConfiguration, Connection
+from bumble import core
+from bumble import hci
+from bumble import rfcomm
+from bumble import transport
+from bumble import utils
+
+
+# -----------------------------------------------------------------------------
+# Constants
+# -----------------------------------------------------------------------------
+DEFAULT_RFCOMM_UUID = "E6D55659-C8B4-4B85-96BB-B1143AF6D3AE"
+DEFAULT_MTU = 4096
+DEFAULT_CLIENT_TCP_PORT = 9544
+DEFAULT_SERVER_TCP_PORT = 9545
+
+TRACE_MAX_SIZE = 48
+
+
+# -----------------------------------------------------------------------------
+class Tracer:
+    """
+    Trace data buffers transmitted from one endpoint to another, with stats.
+    """
+
+    def __init__(self, channel_name: str) -> None:
+        self.channel_name = channel_name
+        self.last_ts: float = 0.0
+
+    def trace_data(self, data: bytes) -> None:
+        now = time.time()
+        elapsed_s = now - self.last_ts if self.last_ts else 0
+        elapsed_ms = int(elapsed_s * 1000)
+        instant_throughput_kbps = ((len(data) / elapsed_s) / 1000) if elapsed_s else 0.0
+
+        hex_str = data[:TRACE_MAX_SIZE].hex() + (
+            "..." if len(data) > TRACE_MAX_SIZE else ""
+        )
+        print(
+            f"[{self.channel_name}] {len(data):4} bytes "
+            f"(+{elapsed_ms:4}ms, {instant_throughput_kbps: 7.2f}kB/s) "
+            f" {hex_str}"
+        )
+
+        self.last_ts = now
+
+
+# -----------------------------------------------------------------------------
+class ServerBridge:
+    """
+    RFCOMM server bridge: waits for a peer to connect an RFCOMM channel.
+    The RFCOMM channel may be associated with a UUID published in an SDP service
+    description, or simply be on a system-assigned channel number.
+    When the connection is made, the bridge connects a TCP socket to a remote host and
+    bridges the data in both directions, with flow control.
+    When the RFCOMM channel is closed, the bridge disconnects the TCP socket
+    and waits for a new channel to be connected.
+    """
+
+    READ_CHUNK_SIZE = 4096
+
+    def __init__(
+        self, channel: int, uuid: str, trace: bool, tcp_host: str, tcp_port: int
+    ) -> None:
+        self.device: Optional[Device] = None
+        self.channel = channel
+        self.uuid = uuid
+        self.tcp_host = tcp_host
+        self.tcp_port = tcp_port
+        self.rfcomm_channel: Optional[rfcomm.DLC] = None
+        self.tcp_tracer: Optional[Tracer]
+        self.rfcomm_tracer: Optional[Tracer]
+
+        if trace:
+            self.tcp_tracer = Tracer(color("RFCOMM->TCP", "cyan"))
+            self.rfcomm_tracer = Tracer(color("TCP->RFCOMM", "magenta"))
+        else:
+            self.rfcomm_tracer = None
+            self.tcp_tracer = None
+
+    async def start(self, device: Device) -> None:
+        self.device = device
+
+        # Create and register a server
+        rfcomm_server = rfcomm.Server(self.device)
+
+        # Listen for incoming DLC connections
+        self.channel = rfcomm_server.listen(self.on_rfcomm_channel, self.channel)
+
+        # Setup the SDP to advertise this channel
+        service_record_handle = 0x00010001
+        self.device.sdp_service_records = {
+            service_record_handle: rfcomm.make_service_sdp_records(
+                service_record_handle, self.channel, core.UUID(self.uuid)
+            )
+        }
+
+        # We're ready for a connection
+        self.device.on("connection", self.on_connection)
+        await self.set_available(True)
+
+        print(
+            color(
+                (
+                    f"### Listening for RFCOMM connection on {device.public_address}, "
+                    f"channel {self.channel}"
+                ),
+                "yellow",
+            )
+        )
+
+    async def set_available(self, available: bool):
+        # Become discoverable and connectable
+        assert self.device
+        await self.device.set_connectable(available)
+        await self.device.set_discoverable(available)
+
+    def on_connection(self, connection):
+        print(color(f"@@@ Bluetooth connection: {connection}", "blue"))
+        connection.on("disconnection", self.on_disconnection)
+
+        # Don't accept new connections until we're disconnected
+        utils.AsyncRunner.spawn(self.set_available(False))
+
+    def on_disconnection(self, reason: int):
+        print(
+            color("@@@ Bluetooth disconnection:", "red"),
+            hci.HCI_Constant.error_name(reason),
+        )
+
+        # We're ready for a new connection
+        utils.AsyncRunner.spawn(self.set_available(True))
+
+    # Called when an RFCOMM channel is established
+    @utils.AsyncRunner.run_in_task()
+    async def on_rfcomm_channel(self, rfcomm_channel):
+        print(color("*** RFCOMM channel:", "cyan"), rfcomm_channel)
+
+        # Connect to the TCP server
+        print(
+            color(
+                f"### Connecting to TCP {self.tcp_host}:{self.tcp_port}",
+                "yellow",
+            )
+        )
+        try:
+            reader, writer = await asyncio.open_connection(self.tcp_host, self.tcp_port)
+        except OSError:
+            print(color("!!! Connection failed", "red"))
+            await rfcomm_channel.disconnect()
+            return
+
+        # Pipe data from RFCOMM to TCP
+        def on_rfcomm_channel_closed():
+            print(color("*** RFCOMM channel closed", "cyan"))
+            writer.close()
+
+        def write_rfcomm_data(data):
+            if self.rfcomm_tracer:
+                self.rfcomm_tracer.trace_data(data)
+
+            writer.write(data)
+
+        rfcomm_channel.sink = write_rfcomm_data
+        rfcomm_channel.on("close", on_rfcomm_channel_closed)
+
+        # Pipe data from TCP to RFCOMM
+        while True:
+            try:
+                data = await reader.read(self.READ_CHUNK_SIZE)
+
+                if len(data) == 0:
+                    print(color("### TCP end of stream", "yellow"))
+                    if rfcomm_channel.state == rfcomm.DLC.State.CONNECTED:
+                        await rfcomm_channel.disconnect()
+                    return
+
+                if self.tcp_tracer:
+                    self.tcp_tracer.trace_data(data)
+
+                rfcomm_channel.write(data)
+                await rfcomm_channel.drain()
+            except Exception as error:
+                print(f"!!! Exception: {error}")
+                break
+
+        writer.close()
+        await writer.wait_closed()
+        print(color("~~~ Bye bye", "magenta"))
+
+
+# -----------------------------------------------------------------------------
+class ClientBridge:
+    """
+    RFCOMM client bridge: connects to a BR/EDR device, then waits for an inbound
+    TCP connection on a specified port number. When a TCP client connects, an
+    RFCOMM connection to the device is established, and the data is bridged in both
+    directions, with flow control.
+    When the TCP connection is closed by the client, the RFCOMM channel is
+    disconnected, but the connection to the device remains, ready for a new TCP client
+    to connect.
+    """
+
+    READ_CHUNK_SIZE = 4096
+
+    def __init__(
+        self,
+        channel: int,
+        uuid: str,
+        trace: bool,
+        address: str,
+        tcp_host: str,
+        tcp_port: int,
+        encrypt: bool,
+    ):
+        self.channel = channel
+        self.uuid = uuid
+        self.trace = trace
+        self.address = address
+        self.tcp_host = tcp_host
+        self.tcp_port = tcp_port
+        self.encrypt = encrypt
+        self.device: Optional[Device] = None
+        self.connection: Optional[Connection] = None
+        self.rfcomm_client: Optional[rfcomm.Client]
+        self.rfcomm_mux: Optional[rfcomm.Multiplexer]
+        self.tcp_connected: bool = False
+
+        self.tcp_tracer: Optional[Tracer]
+        self.rfcomm_tracer: Optional[Tracer]
+
+        if trace:
+            self.tcp_tracer = Tracer(color("RFCOMM->TCP", "cyan"))
+            self.rfcomm_tracer = Tracer(color("TCP->RFCOMM", "magenta"))
+        else:
+            self.rfcomm_tracer = None
+            self.tcp_tracer = None
+
+    async def connect(self) -> None:
+        if self.connection:
+            return
+
+        print(color(f"@@@ Connecting to Bluetooth {self.address}", "blue"))
+        assert self.device
+        self.connection = await self.device.connect(
+            self.address, transport=core.BT_BR_EDR_TRANSPORT
+        )
+        print(color(f"@@@ Bluetooth connection: {self.connection}", "blue"))
+        self.connection.on("disconnection", self.on_disconnection)
+
+        if self.encrypt:
+            print(color("@@@ Encrypting Bluetooth connection", "blue"))
+            await self.connection.encrypt()
+            print(color("@@@ Bluetooth connection encrypted", "blue"))
+
+        self.rfcomm_client = rfcomm.Client(self.connection)
+        try:
+            self.rfcomm_mux = await self.rfcomm_client.start()
+        except BaseException as e:
+            print(color("!!! Failed to setup RFCOMM connection", "red"), e)
+            raise
+
+    async def start(self, device: Device) -> None:
+        self.device = device
+        await device.set_connectable(False)
+        await device.set_discoverable(False)
+
+        # Called when a TCP connection is established
+        async def on_tcp_connection(reader, writer):
+            print(color("<<< TCP connection", "magenta"))
+            if self.tcp_connected:
+                print(
+                    color("!!! TCP connection already active, rejecting new one", "red")
+                )
+                writer.close()
+                return
+            self.tcp_connected = True
+
+            try:
+                await self.pipe(reader, writer)
+            except BaseException as error:
+                print(color("!!! Exception while piping data:", "red"), error)
+                return
+            finally:
+                writer.close()
+                await writer.wait_closed()
+                self.tcp_connected = False
+
+        await asyncio.start_server(
+            on_tcp_connection,
+            host=self.tcp_host if self.tcp_host != "_" else None,
+            port=self.tcp_port,
+        )
+        print(
+            color(
+                f"### Listening for TCP connections on port {self.tcp_port}", "magenta"
+            )
+        )
+
+    async def pipe(
+        self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter
+    ) -> None:
+        # Resolve the channel number from the UUID if needed
+        if self.channel == 0:
+            await self.connect()
+            assert self.connection
+            channel = await rfcomm.find_rfcomm_channel_with_uuid(
+                self.connection, self.uuid
+            )
+            if channel:
+                print(color(f"### Found RFCOMM channel {channel}", "yellow"))
+            else:
+                print(color(f"!!! RFCOMM channel with UUID {self.uuid} not found"))
+                return
+        else:
+            channel = self.channel
+
+        # Connect a new RFCOMM channel
+        await self.connect()
+        assert self.rfcomm_mux
+        print(color(f"*** Opening RFCOMM channel {channel}", "green"))
+        try:
+            rfcomm_channel = await self.rfcomm_mux.open_dlc(channel)
+            print(color(f"*** RFCOMM channel open: {rfcomm_channel}", "green"))
+        except Exception as error:
+            print(color(f"!!! RFCOMM open failed: {error}", "red"))
+            return
+
+        # Pipe data from RFCOMM to TCP
+        def on_rfcomm_channel_closed():
+            print(color("*** RFCOMM channel closed", "green"))
+
+        def write_rfcomm_data(data):
+            if self.trace:
+                self.rfcomm_tracer.trace_data(data)
+
+            writer.write(data)
+
+        rfcomm_channel.on("close", on_rfcomm_channel_closed)
+        rfcomm_channel.sink = write_rfcomm_data
+
+        # Pipe data from TCP to RFCOMM
+        while True:
+            try:
+                data = await reader.read(self.READ_CHUNK_SIZE)
+
+                if len(data) == 0:
+                    print(color("### TCP end of stream", "yellow"))
+                    if rfcomm_channel.state == rfcomm.DLC.State.CONNECTED:
+                        await rfcomm_channel.disconnect()
+                    self.tcp_connected = False
+                    return
+
+                if self.tcp_tracer:
+                    self.tcp_tracer.trace_data(data)
+
+                rfcomm_channel.write(data)
+                await rfcomm_channel.drain()
+            except Exception as error:
+                print(f"!!! Exception: {error}")
+                break
+
+        print(color("~~~ Bye bye", "magenta"))
+
+    def on_disconnection(self, reason: int) -> None:
+        print(
+            color("@@@ Bluetooth disconnection:", "red"),
+            hci.HCI_Constant.error_name(reason),
+        )
+        self.connection = None
+
+
+# -----------------------------------------------------------------------------
+async def run(device_config, hci_transport, bridge):
+    print("<<< connecting to HCI...")
+    async with await transport.open_transport_or_link(hci_transport) as (
+        hci_source,
+        hci_sink,
+    ):
+        print("<<< connected")
+
+        if device_config:
+            device = Device.from_config_file_with_hci(
+                device_config, hci_source, hci_sink
+            )
+        else:
+            device = Device.from_config_with_hci(
+                DeviceConfiguration(), hci_source, hci_sink
+            )
+        device.classic_enabled = True
+
+        # Let's go
+        await device.power_on()
+        try:
+            await bridge.start(device)
+
+            # Wait until the transport terminates
+            await hci_source.wait_for_termination()
+        except core.ConnectionError as error:
+            print(color(f"!!! Bluetooth connection failed: {error}", "red"))
+        except Exception as error:
+            print(f"Exception while running bridge: {error}")
+
+
+# -----------------------------------------------------------------------------
+@click.group()
+@click.pass_context
+@click.option(
+    "--device-config",
+    metavar="CONFIG_FILE",
+    help="Device configuration file",
+)
+@click.option(
+    "--hci-transport", metavar="TRANSPORT_NAME", help="HCI transport", required=True
+)
+@click.option("--trace", is_flag=True, help="Trace bridged data to stdout")
+@click.option(
+    "--channel",
+    metavar="CHANNEL_NUMER",
+    help="RFCOMM channel number",
+    type=int,
+    default=0,
+)
+@click.option(
+    "--uuid",
+    metavar="UUID",
+    help="UUID for the RFCOMM channel",
+    default=DEFAULT_RFCOMM_UUID,
+)
+def cli(
+    context,
+    device_config,
+    hci_transport,
+    trace,
+    channel,
+    uuid,
+):
+    context.ensure_object(dict)
+    context.obj["device_config"] = device_config
+    context.obj["hci_transport"] = hci_transport
+    context.obj["trace"] = trace
+    context.obj["channel"] = channel
+    context.obj["uuid"] = uuid
+
+
+# -----------------------------------------------------------------------------
+@cli.command()
+@click.pass_context
+@click.option("--tcp-host", help="TCP host", default="localhost")
+@click.option("--tcp-port", help="TCP port", default=DEFAULT_SERVER_TCP_PORT)
+def server(context, tcp_host, tcp_port):
+    bridge = ServerBridge(
+        context.obj["channel"],
+        context.obj["uuid"],
+        context.obj["trace"],
+        tcp_host,
+        tcp_port,
+    )
+    asyncio.run(run(context.obj["device_config"], context.obj["hci_transport"], bridge))
+
+
+# -----------------------------------------------------------------------------
+@cli.command()
+@click.pass_context
+@click.argument("bluetooth-address")
+@click.option("--tcp-host", help="TCP host", default="_")
+@click.option("--tcp-port", help="TCP port", default=DEFAULT_CLIENT_TCP_PORT)
+@click.option("--encrypt", is_flag=True, help="Encrypt the connection")
+def client(context, bluetooth_address, tcp_host, tcp_port, encrypt):
+    bridge = ClientBridge(
+        context.obj["channel"],
+        context.obj["uuid"],
+        context.obj["trace"],
+        bluetooth_address,
+        tcp_host,
+        tcp_port,
+        encrypt,
+    )
+    asyncio.run(run(context.obj["device_config"], context.obj["hci_transport"], bridge))
+
+
+# -----------------------------------------------------------------------------
+logging.basicConfig(level=os.environ.get("BUMBLE_LOGLEVEL", "WARNING").upper())
+if __name__ == "__main__":
+    cli(obj={})  # pylint: disable=no-value-for-parameter

bumble/l2cap.py

@@ -70,6 +70,7 @@ L2CAP_LE_SIGNALING_CID = 0x05
 
 L2CAP_MIN_LE_MTU     = 23
 L2CAP_MIN_BR_EDR_MTU = 48
+L2CAP_MAX_BR_EDR_MTU = 65535
 
 L2CAP_DEFAULT_MTU = 2048  # Default value for the MTU we are willing to accept
 
@@ -832,7 +833,9 @@ class ClassicChannel(EventEmitter):
 
         # Wait for the connection to succeed or fail
         try:
-            return await self.connection_result
+            return await self.connection.abort_on(
+                'disconnection', self.connection_result
+            )
         finally:
             self.connection_result = None
 
@@ -2225,7 +2228,7 @@ class ChannelManager:
         # Connect
         try:
             await channel.connect()
-        except Exception as e:
+        except BaseException as e:
             del connection_channels[source_cid]
             raise e
 

bumble/rfcomm.py

@@ -106,9 +106,11 @@ CRC_TABLE = bytes([
     0XBA, 0X2B, 0X59, 0XC8, 0XBD, 0X2C, 0X5E, 0XCF
 ])
 
-RFCOMM_DEFAULT_L2CAP_MTU      = 2048
+RFCOMM_DEFAULT_L2CAP_MTU        = 2048
-RFCOMM_DEFAULT_WINDOW_SIZE    = 7
+RFCOMM_DEFAULT_INITIAL_CREDITS  = 7
-RFCOMM_DEFAULT_MAX_FRAME_SIZE = 2000
+RFCOMM_DEFAULT_MAX_CREDITS      = 32
+RFCOMM_DEFAULT_CREDIT_THRESHOLD = RFCOMM_DEFAULT_MAX_CREDITS // 2
+RFCOMM_DEFAULT_MAX_FRAME_SIZE   = 2000
 
 RFCOMM_DYNAMIC_CHANNEL_NUMBER_START = 1
 RFCOMM_DYNAMIC_CHANNEL_NUMBER_END   = 30
@@ -365,12 +367,12 @@ class RFCOMM_MCC_PN:
     ack_timer: int
     max_frame_size: int
     max_retransmissions: int
-    window_size: int
+    initial_credits: int
 
     def __post_init__(self) -> None:
-        if self.window_size < 1 or self.window_size > 7:
+        if self.initial_credits < 1 or self.initial_credits > 7:
             logger.warning(
-                f'Error Recovery Window size {self.window_size} is out of range [1, 7].'
+                f'Initial credits {self.initial_credits} is out of range [1, 7].'
             )
 
     @staticmethod
@@ -382,7 +384,7 @@ class RFCOMM_MCC_PN:
             ack_timer=data[3],
             max_frame_size=data[4] | data[5] << 8,
             max_retransmissions=data[6],
-            window_size=data[7] & 0x07,
+            initial_credits=data[7] & 0x07,
         )
 
     def __bytes__(self) -> bytes:
@@ -396,7 +398,7 @@ class RFCOMM_MCC_PN:
                 (self.max_frame_size >> 8) & 0xFF,
                 self.max_retransmissions & 0xFF,
                 # Only 3 bits are meaningful.
-                self.window_size & 0x07,
+                self.initial_credits & 0x07,
             ]
         )
 
@@ -446,40 +448,43 @@ class DLC(EventEmitter):
         DISCONNECTED = 0x04
         RESET = 0x05
 
-    connection_result: Optional[asyncio.Future]
-    _sink: Optional[Callable[[bytes], None]]
-    _enqueued_rx_packets: collections.deque[bytes]
-
     def __init__(
         self,
         multiplexer: Multiplexer,
         dlci: int,
-        max_frame_size: int,
+        tx_max_frame_size: int,
-        window_size: int,
+        tx_initial_credits: int,
+        rx_max_frame_size: int,
+        rx_initial_credits: int,
     ) -> None:
         super().__init__()
         self.multiplexer = multiplexer
         self.dlci = dlci
-        self.max_frame_size = max_frame_size
+        self.rx_max_frame_size = rx_max_frame_size
-        self.window_size = window_size
+        self.rx_initial_credits = rx_initial_credits
-        self.rx_credits = window_size
+        self.rx_max_credits = RFCOMM_DEFAULT_MAX_CREDITS
-        self.rx_threshold = window_size // 2
+        self.rx_credits = rx_initial_credits
-        self.tx_credits = window_size
+        self.rx_credits_threshold = RFCOMM_DEFAULT_CREDIT_THRESHOLD
+        self.tx_max_frame_size = tx_max_frame_size
+        self.tx_credits = tx_initial_credits
         self.tx_buffer = b''
         self.state = DLC.State.INIT
         self.role = multiplexer.role
         self.c_r = 1 if self.role == Multiplexer.Role.INITIATOR else 0
-        self.connection_result = None
+        self.connection_result: Optional[asyncio.Future] = None
+        self.disconnection_result: Optional[asyncio.Future] = None
         self.drained = asyncio.Event()
         self.drained.set()
         # Queued packets when sink is not set.
-        self._enqueued_rx_packets = collections.deque(maxlen=DEFAULT_RX_QUEUE_SIZE)
+        self._enqueued_rx_packets: collections.deque[bytes] = collections.deque(
-        self._sink = None
+            maxlen=DEFAULT_RX_QUEUE_SIZE
+        )
+        self._sink: Optional[Callable[[bytes], None]] = None
 
         # Compute the MTU
         max_overhead = 4 + 1  # header with 2-byte length + fcs
         self.mtu = min(
-            max_frame_size, self.multiplexer.l2cap_channel.peer_mtu - max_overhead
+            tx_max_frame_size, self.multiplexer.l2cap_channel.peer_mtu - max_overhead
         )
 
     @property
@@ -525,20 +530,35 @@ class DLC(EventEmitter):
         self.emit('open')
 
     def on_ua_frame(self, _frame: RFCOMM_Frame) -> None:
-        if self.state != DLC.State.CONNECTING:
+        if self.state == DLC.State.CONNECTING:
+            # Exchange the modem status with the peer
+            msc = RFCOMM_MCC_MSC(dlci=self.dlci, fc=0, rtc=1, rtr=1, ic=0, dv=1)
+            mcc = RFCOMM_Frame.make_mcc(mcc_type=MccType.MSC, c_r=1, data=bytes(msc))
+            logger.debug(f'>>> MCC MSC Command: {msc}')
+            self.send_frame(RFCOMM_Frame.uih(c_r=self.c_r, dlci=0, information=mcc))
+
+            self.change_state(DLC.State.CONNECTED)
+            if self.connection_result:
+                self.connection_result.set_result(None)
+                self.connection_result = None
+            self.multiplexer.on_dlc_open_complete(self)
+        elif self.state == DLC.State.DISCONNECTING:
+            self.change_state(DLC.State.DISCONNECTED)
+            if self.disconnection_result:
+                self.disconnection_result.set_result(None)
+                self.disconnection_result = None
+            self.multiplexer.on_dlc_disconnection(self)
+            self.emit('close')
+        else:
             logger.warning(
-                color('!!! received SABM when not in CONNECTING state', 'red')
+                color(
+                    (
+                        '!!! received UA frame when not in '
+                        'CONNECTING or DISCONNECTING state'
+                    ),
+                    'red',
+                )
             )
-            return
-
-        # Exchange the modem status with the peer
-        msc = RFCOMM_MCC_MSC(dlci=self.dlci, fc=0, rtc=1, rtr=1, ic=0, dv=1)
-        mcc = RFCOMM_Frame.make_mcc(mcc_type=MccType.MSC, c_r=1, data=bytes(msc))
-        logger.debug(f'>>> MCC MSC Command: {msc}')
-        self.send_frame(RFCOMM_Frame.uih(c_r=self.c_r, dlci=0, information=mcc))
-
-        self.change_state(DLC.State.CONNECTED)
-        self.multiplexer.on_dlc_open_complete(self)
 
     def on_dm_frame(self, frame: RFCOMM_Frame) -> None:
         # TODO: handle all states
@@ -609,6 +629,19 @@ class DLC(EventEmitter):
         self.connection_result = asyncio.get_running_loop().create_future()
         self.send_frame(RFCOMM_Frame.sabm(c_r=self.c_r, dlci=self.dlci))
 
+    async def disconnect(self) -> None:
+        if self.state != DLC.State.CONNECTED:
+            raise InvalidStateError('invalid state')
+
+        self.disconnection_result = asyncio.get_running_loop().create_future()
+        self.change_state(DLC.State.DISCONNECTING)
+        self.send_frame(
+            RFCOMM_Frame.disc(
+                c_r=1 if self.role == Multiplexer.Role.INITIATOR else 0, dlci=self.dlci
+            )
+        )
+        await self.disconnection_result
+
     def accept(self) -> None:
         if self.state != DLC.State.INIT:
             raise InvalidStateError('invalid state')
@@ -618,9 +651,9 @@ class DLC(EventEmitter):
             cl=0xE0,
             priority=7,
             ack_timer=0,
-            max_frame_size=self.max_frame_size,
+            max_frame_size=self.rx_max_frame_size,
             max_retransmissions=0,
-            window_size=self.window_size,
+            initial_credits=self.rx_initial_credits,
         )
         mcc = RFCOMM_Frame.make_mcc(mcc_type=MccType.PN, c_r=0, data=bytes(pn))
         logger.debug(f'>>> PN Response: {pn}')
@@ -628,8 +661,8 @@ class DLC(EventEmitter):
         self.change_state(DLC.State.CONNECTING)
 
     def rx_credits_needed(self) -> int:
-        if self.rx_credits <= self.rx_threshold:
+        if self.rx_credits <= self.rx_credits_threshold:
-            return self.window_size - self.rx_credits
+            return self.rx_max_credits - self.rx_credits
 
         return 0
 
@@ -689,6 +722,17 @@ class DLC(EventEmitter):
     async def drain(self) -> None:
         await self.drained.wait()
 
+    def abort(self) -> None:
+        logger.debug(f'aborting DLC: {self}')
+        if self.connection_result:
+            self.connection_result.cancel()
+            self.connection_result = None
+        if self.disconnection_result:
+            self.disconnection_result.cancel()
+            self.disconnection_result = None
+        self.change_state(DLC.State.RESET)
+        self.emit('close')
+
     def __str__(self) -> str:
         return f'DLC(dlci={self.dlci},state={self.state.name})'
 
@@ -711,7 +755,7 @@ class Multiplexer(EventEmitter):
     connection_result: Optional[asyncio.Future]
     disconnection_result: Optional[asyncio.Future]
     open_result: Optional[asyncio.Future]
-    acceptor: Optional[Callable[[int], bool]]
+    acceptor: Optional[Callable[[int], Optional[Tuple[int, int]]]]
     dlcs: Dict[int, DLC]
 
     def __init__(self, l2cap_channel: l2cap.ClassicChannel, role: Role) -> None:
@@ -723,11 +767,15 @@ class Multiplexer(EventEmitter):
         self.connection_result = None
         self.disconnection_result = None
         self.open_result = None
+        self.open_pn: Optional[RFCOMM_MCC_PN] = None
+        self.open_rx_max_credits = 0
         self.acceptor = None
 
         # Become a sink for the L2CAP channel
         l2cap_channel.sink = self.on_pdu
 
+        l2cap_channel.on('close', self.on_l2cap_channel_close)
+
     def change_state(self, new_state: State) -> None:
         logger.debug(f'{self} state change -> {color(new_state.name, "cyan")}')
         self.state = new_state
@@ -791,6 +839,7 @@ class Multiplexer(EventEmitter):
                         'rfcomm',
                     )
                 )
+                self.open_result = None
         else:
             logger.warning(f'unexpected state for DM: {self}')
 
@@ -828,9 +877,16 @@ class Multiplexer(EventEmitter):
             else:
                 if self.acceptor:
                     channel_number = pn.dlci >> 1
-                    if self.acceptor(channel_number):
+                    if dlc_params := self.acceptor(channel_number):
                         # Create a new DLC
-                        dlc = DLC(self, pn.dlci, pn.max_frame_size, pn.window_size)
+                        dlc = DLC(
+                            self,
+                            dlci=pn.dlci,
+                            tx_max_frame_size=pn.max_frame_size,
+                            tx_initial_credits=pn.initial_credits,
+                            rx_max_frame_size=dlc_params[0],
+                            rx_initial_credits=dlc_params[1],
+                        )
                         self.dlcs[pn.dlci] = dlc
 
                         # Re-emit the handshake completion event
@@ -848,8 +904,17 @@ class Multiplexer(EventEmitter):
             # Response
             logger.debug(f'>>> PN Response: {pn}')
             if self.state == Multiplexer.State.OPENING:
-                dlc = DLC(self, pn.dlci, pn.max_frame_size, pn.window_size)
+                assert self.open_pn
+                dlc = DLC(
+                    self,
+                    dlci=pn.dlci,
+                    tx_max_frame_size=pn.max_frame_size,
+                    tx_initial_credits=pn.initial_credits,
+                    rx_max_frame_size=self.open_pn.max_frame_size,
+                    rx_initial_credits=self.open_pn.initial_credits,
+                )
                 self.dlcs[pn.dlci] = dlc
+                self.open_pn = None
                 dlc.connect()
             else:
                 logger.warning('ignoring PN response')
@@ -887,7 +952,7 @@ class Multiplexer(EventEmitter):
         self,
         channel: int,
         max_frame_size: int = RFCOMM_DEFAULT_MAX_FRAME_SIZE,
-        window_size: int = RFCOMM_DEFAULT_WINDOW_SIZE,
+        initial_credits: int = RFCOMM_DEFAULT_INITIAL_CREDITS,
     ) -> DLC:
         if self.state != Multiplexer.State.CONNECTED:
             if self.state == Multiplexer.State.OPENING:
@@ -895,17 +960,19 @@ class Multiplexer(EventEmitter):
 
             raise InvalidStateError('not connected')
 
-        pn = RFCOMM_MCC_PN(
+        self.open_pn = RFCOMM_MCC_PN(
             dlci=channel << 1,
             cl=0xF0,
             priority=7,
             ack_timer=0,
             max_frame_size=max_frame_size,
             max_retransmissions=0,
-            window_size=window_size,
+            initial_credits=initial_credits,
         )
-        mcc = RFCOMM_Frame.make_mcc(mcc_type=MccType.PN, c_r=1, data=bytes(pn))
+        mcc = RFCOMM_Frame.make_mcc(
-        logger.debug(f'>>> Sending MCC: {pn}')
+            mcc_type=MccType.PN, c_r=1, data=bytes(self.open_pn)
+        )
+        logger.debug(f'>>> Sending MCC: {self.open_pn}')
         self.open_result = asyncio.get_running_loop().create_future()
         self.change_state(Multiplexer.State.OPENING)
         self.send_frame(
@@ -915,15 +982,31 @@ class Multiplexer(EventEmitter):
                 information=mcc,
             )
         )
-        result = await self.open_result
+        return await self.open_result
-        self.open_result = None
-        return result
 
     def on_dlc_open_complete(self, dlc: DLC) -> None:
         logger.debug(f'DLC [{dlc.dlci}] open complete')
+
         self.change_state(Multiplexer.State.CONNECTED)
+
         if self.open_result:
             self.open_result.set_result(dlc)
+            self.open_result = None
+
+    def on_dlc_disconnection(self, dlc: DLC) -> None:
+        logger.debug(f'DLC [{dlc.dlci}] disconnection')
+        self.dlcs.pop(dlc.dlci, None)
+
+    def on_l2cap_channel_close(self) -> None:
+        logger.debug('L2CAP channel closed, cleaning up')
+        if self.open_result:
+            self.open_result.cancel()
+            self.open_result = None
+        if self.disconnection_result:
+            self.disconnection_result.cancel()
+            self.disconnection_result = None
+        for dlc in self.dlcs.values():
+            dlc.abort()
 
     def __str__(self) -> str:
         return f'Multiplexer(state={self.state.name})'
@@ -982,15 +1065,13 @@ class Client:
 
 # -----------------------------------------------------------------------------
 class Server(EventEmitter):
-    acceptors: Dict[int, Callable[[DLC], None]]
-
     def __init__(
         self, device: Device, l2cap_mtu: int = RFCOMM_DEFAULT_L2CAP_MTU
     ) -> None:
         super().__init__()
         self.device = device
-        self.multiplexer = None
+        self.acceptors: Dict[int, Callable[[DLC], None]] = {}
-        self.acceptors = {}
+        self.dlc_configs: Dict[int, Tuple[int, int]] = {}
 
         # Register ourselves with the L2CAP channel manager
         self.l2cap_server = device.create_l2cap_server(
@@ -998,7 +1079,13 @@ class Server(EventEmitter):
             handler=self.on_connection,
         )
 
-    def listen(self, acceptor: Callable[[DLC], None], channel: int = 0) -> int:
+    def listen(
+        self,
+        acceptor: Callable[[DLC], None],
+        channel: int = 0,
+        max_frame_size: int = RFCOMM_DEFAULT_MAX_FRAME_SIZE,
+        initial_credits: int = RFCOMM_DEFAULT_INITIAL_CREDITS,
+    ) -> int:
         if channel:
             if channel in self.acceptors:
                 # Busy
@@ -1018,6 +1105,8 @@ class Server(EventEmitter):
                 return 0
 
         self.acceptors[channel] = acceptor
+        self.dlc_configs[channel] = (max_frame_size, initial_credits)
+
         return channel
 
     def on_connection(self, l2cap_channel: l2cap.ClassicChannel) -> None:
@@ -1035,15 +1124,14 @@ class Server(EventEmitter):
         # Notify
         self.emit('start', multiplexer)
 
-    def accept_dlc(self, channel_number: int) -> bool:
+    def accept_dlc(self, channel_number: int) -> Optional[Tuple[int, int]]:
-        return channel_number in self.acceptors
+        return self.dlc_configs.get(channel_number)
 
     def on_dlc(self, dlc: DLC) -> None:
         logger.debug(f'@@@ new DLC connected: {dlc}')
 
         # Let the acceptor know
-        acceptor = self.acceptors.get(dlc.dlci >> 1)
+        if acceptor := self.acceptors.get(dlc.dlci >> 1):
-        if acceptor:
             acceptor(dlc)
 
     def __enter__(self) -> Self:

bumble/sdp.py

@@ -997,7 +997,7 @@ class Server:
             try:
                 handler(sdp_pdu)
             except Exception as error:
-                logger.warning(f'{color("!!! Exception in handler:", "red")} {error}')
+                logger.exception(f'{color("!!! Exception in handler:", "red")} {error}')
                 self.send_response(
                     SDP_ErrorResponse(
                         transaction_id=sdp_pdu.transaction_id,

extras/android/BtBench/app/src/main/java/com/github/google/bumble/btbench/SocketClient.kt

@@ -56,13 +56,19 @@ class SocketClient(private val viewModel: AppViewModel, private val socket: Blue
 
             thread {
                 socketDataSource.receive()
+                socket.close()
+                sender.abort()
             }
 
             Log.info("Startup delay: $DEFAULT_STARTUP_DELAY")
             Thread.sleep(DEFAULT_STARTUP_DELAY.toLong());
             Log.info("Starting to send")
 
-            sender.run()
+            try {
+                sender.run()
+            } catch (error: IOException) {
+                Log.info("run ended abruptly")
+            }
             cleanup()
         }
     }

setup.cfg

@@ -62,6 +62,7 @@ console_scripts =
     bumble-gatt-dump = bumble.apps.gatt_dump:main
     bumble-hci-bridge = bumble.apps.hci_bridge:main
     bumble-l2cap-bridge = bumble.apps.l2cap_bridge:main
+    bumble-rfcomm-bridge = bumble.apps.rfcomm_bridge:main
     bumble-pair = bumble.apps.pair:main
     bumble-scan = bumble.apps.scan:main
     bumble-show = bumble.apps.show:main

tests/rfcomm_test.py

@@ -62,7 +62,7 @@ def test_frames():
 
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio
-async def test_basic_connection() -> None:
+async def test_connection_and_disconnection() -> None:
     devices = test_utils.TwoDevices()
     await devices.setup_connection()
 
@@ -83,6 +83,11 @@ async def test_basic_connection() -> None:
     dlcs[1].write(b'Lorem ipsum dolor sit amet')
     assert await queues[0].get() == b'Lorem ipsum dolor sit amet'
 
+    closed = asyncio.Event()
+    dlcs[1].on('close', closed.set)
+    await dlcs[1].disconnect()
+    await closed.wait()
+
 
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio