java - 区分 "out of range"或 "in range, but no listening server socket"？ (蓝牙)

Question

问题

我如何区分无法与远程 Android 设备建立蓝牙连接是因为:

• 场景 1:远程设备不在范围内，或者其蓝牙已禁用。
• 场景 2:远程设备在范围内，但远程设备上没有服务器套接字来接受我的连接。

我尝试过的

1. 我无法区分连接时抛出的异常，因为它在两种情况下抛出了相同的异常:

   java.io.IOException: read failed, socket might closed or timeout, read ret -1
   

2. 我无法使用fetchUuidsWithSdp() 来检查远程设备是否支持我的 UUID，因为它在任何一种情况下的行为都相同... according to the documentation :

   This API is asynchronous and {@link #ACTION_UUID} intent is sent, with the UUIDs supported by the remote end. If there is an error in getting the SDP records or if the process takes a long time, {@link #ACTION_UUID} intent is sent with the UUIDs that is currently present in the cache...

   根据 this SO thread，它的行为似乎也有点不可预测。

3. 最后，我不想使用sdpSearch来区分两者，因为它是在 API 23 中添加的，我希望能够支持低至 API 19。

Answer 1

您可以通过尝试连接到通常在 Android 设备上可用的标准 UUID 来确定设备是否在范围内。如果调用连接:

• 失败，然后远程设备超出范围或其蓝牙被禁用。
• 成功，则远程设备在范围内，您应该关闭连接，然后尝试连接到您应用的 UUID...如果失败，则没有监听套接字...如果成功，则一切正常好吧。

示例代码:

public BluetoothSocket connect(BluetoothDevice remoteDevice) throws IOException
{
    OPP_UUID = UUID.fromString("00001105-0000-1000-8000-00805f9b34fb");

    // check if remote device is in range...throw exception if out of range
    try
    {
        BluetoothSocket socket = remoteDevice
            .createRfcommSocketToServiceRecord(OPP_UUID);
        socket.connect();
        socket.close();
    }
    catch(IOException ex)
    {
        throw new IOException("out of range",ex);
    }

    // try to connect to service on remote device...throw exception if UUID
    // is not available
    try
    {
        BluetoothSocket socket = remoteDevice
            .createRfcommSocketToServiceRecord(MY_UUID);
        socket.connect();
        return socket;
    }
    catch(IOException ex)
    {
        throw new IOException("no listening server socket",ex);
    }
}

我用了BluetoothDevice.getUuids()获取我的一台 Android 设备上可用的 UUID。它给了我这个列表:

0000110a-0000-1000-8000-00805f9b34fb - Advanced Audio Distribution Profile (0x110a)
00001105-0000-1000-8000-00805f9b34fb - Object Push Profile (0x1105) // least invasive one...it seems
00001115-0000-1000-8000-00805f9b34fb - Personal Area Networking Profile (0x1115)
0000112f-0000-1000-8000-00805f9b34fb - Phonebook Access (0x112f) // this works!
00001112-0000-1000-8000-00805f9b34fb - Headset - Audio Gateway (0x1112)
0000111f-0000-1000-8000-00805f9b34fb - Handsfree Audio Gateway (0x111f)
00001132-0000-1000-8000-00805f9b34fb - Message Access Profile (0x1132) // this works too!
00000000-0000-1000-8000-00805f9b34fb - Base UUID (0x0000) // couldn't get this to work :(

Standard UUIDs from Bluetooth spec.