Python基于pyjnius开发安卓蓝牙客户端连接报socket读取失败如何解决

问题根因 #

你遇到的jnius.jnius.JavaException: JVM exception occurred: read failed, socket might closed or timeout, read ret: -1是Android蓝牙框架的经典兼容性问题，官方提供的createRfcommSocketToServiceRecord方法在部分设备、Android版本上无法正确匹配RFCOMM通道，需要通过反射调用系统隐藏的方法直接指定端口号连接。

完整可运行代码 #

from jnius import autoclass, JavaException


server_mac_address = '94:08:53:52:B5:98'
uuid = "00001101-0000-1000-8000-00805F9B34FB"

BluetoothAdapter = autoclass('android.bluetooth.BluetoothAdapter')
BluetoothDevice = autoclass('android.bluetooth.BluetoothDevice')
BluetoothSocket = autoclass('android.bluetooth.BluetoothSocket')
UUID = autoclass('java.util.UUID')
Integer = autoclass('java.lang.Integer')

def get_socket_stream():
    adapter = BluetoothAdapter.getDefaultAdapter()
    device = adapter.getRemoteDevice(server_mac_address)
    socket = None
    # 先尝试标准方法，失败后走反射 fallback 方案
    try:
        socket = device.createRfcommSocketToServiceRecord(UUID.fromString(uuid))
        adapter.cancelDiscovery()
        socket.connect()
    except JavaException:
        # 反射调用隐藏方法，指定RFCOMM通道1，和pybluez默认rfcomm-server端口对应
        create_rfcomm_method = device.getClass().getMethod("createRfcommSocket", [Integer.TYPE])
        socket = create_rfcomm_method.invoke(device, 1)
        adapter.cancelDiscovery()
        socket.connect()

    recv_stream = socket.getInputStream()
    send_stream = socket.getOutputStream()

    return recv_stream, send_stream

if __name__ == '__main__':
    recv_stream, send_stream = get_socket_stream()
    # 注意转换为bytes传输，否则会抛类型错误
    send_stream.write('hello\n'.encode('utf-8'))
    send_stream.flush()

必做检查项 #

• 确认你运行的pybluez服务端用的是默认端口1：如果修改过rfcomm-server.py的port参数，将代码里create_rfcomm_method.invoke(device, 1)的1替换为你实际使用的端口号
• 确认APP已拿到全部蓝牙权限：Android 12及以上需要申请BLUETOOTH_SCAN、BLUETOOTH_CONNECT、ACCESS_FINE_LOCATION权限，Android 11及以下需要BLUETOOTH、BLUETOOTH_ADMIN、ACCESS_COARSE_LOCATION权限，未授权会直接导致连接失败
• 确认连接时蓝牙没有在执行其他扫描任务：扫描会占用蓝牙硬件带宽，导致连接超时，代码里的cancelDiscovery()必须保留
• 确认设备配对状态正常：如果配对失效，先删除两端的配对记录，重新配对后再运行代码

内容的提问来源于stack exchange，提问作者Kirill