BluetoothGattServer始终在30秒后断开连接

Question

我一直试图找出如何通过蓝牙让这些手机相互通话。我将android手机设置为外设，我的iPhone运行nrf connect app。我可以通过iPhone广告并连接到Android手机，我可以订阅通知并查看更新的特性。问题是如果我不发送特征通知，大约7-10秒后连接就会丢失。我得到了connectionStateChanged回调处理程序的回调，我无法弄清楚是什么导致了这一点。我不认为这是nrf应用程序，因为我已经连接到其他东西，它只是永远保持联系。有什么我想念的吗？

这是一些代码：

private BluetoothManager bluetoothManager;
private BluetoothGattServer gattServer;
private BluetoothGattCharacteristic test_characteristic;
private BluetoothDevice connected_device;


private BluetoothGattServerCallback gattServerCallback = new BluetoothGattServerCallback() {
    @Override
    public void onConnectionStateChange(BluetoothDevice device, int status, int newState) {
        super.onConnectionStateChange(device, status, newState);
        if (newState == 2){ //CONNECTED
            connected_device = device;
        }
        Log.i("chase", "Connection state changed: "+newState);
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    BluetoothRegulator.sharedInstance().appContext = getApplicationContext();
    bluetoothManager = (android.bluetooth.BluetoothManager) this.getSystemService(Context.BLUETOOTH_SERVICE);
    BluetoothRegulator.sharedInstance().initialize(bluetoothManager);

    if( ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION}, 1);
    }


    gattServer = bluetoothManager.openGattServer(this, gattServerCallback);
    String uuid_string = "92D9D153-9BE6-43FF-9672-3E2904628B9D";
    BluetoothGattService service = new BluetoothGattService(UUID.fromString(uuid_string), BluetoothGattService.SERVICE_TYPE_PRIMARY);

    uuid_string = "43FF0001-9BE6-43FF-9672-3E2904628B9D";
    test_characteristic = new BluetoothGattCharacteristic(
            UUID.fromString(uuid_string),
            BluetoothGattCharacteristic.PROPERTY_BROADCAST | BluetoothGattCharacteristic.PROPERTY_NOTIFY | BluetoothGattCharacteristic.PROPERTY_READ | BluetoothGattCharacteristic.PROPERTY_WRITE,
            BluetoothGattCharacteristic.PERMISSION_READ | BluetoothGattCharacteristic.PERMISSION_WRITE);
    test_characteristic.setValue( ""+System.currentTimeMillis() );
    service.addCharacteristic(test_characteristic);
    gattServer.addService(service);

    findViewById(R.id.send_data_btn).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            shot_detected_characteristic.setValue( ""+System.currentTimeMillis() );
            gattServer.notifyCharacteristicChanged(connected_device, shot_detected_characteristic, false);
        }
    });

    findViewById(R.id.advertise).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            advertise();
        }
    });

}
private void advertise() {
    BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
    BluetoothLeAdvertiser advertiser = adapter.getBluetoothLeAdvertiser();
    AdvertiseSettings settings = new AdvertiseSettings.Builder()
            .setAdvertiseMode( AdvertiseSettings.ADVERTISE_MODE_LOW_LATENCY )
            .setTxPowerLevel( AdvertiseSettings.ADVERTISE_TX_POWER_HIGH )
            .setConnectable( true )
            .build();
    String uuid_string = "92C9D164-9BE6-43FF-9672-3E2804618B9C";
    ParcelUuid pUuid = new ParcelUuid( UUID.fromString( uuid_string ) );

    AdvertiseData data = new AdvertiseData.Builder()
            .setIncludeDeviceName( true )
            .addServiceData( pUuid, "TEST".getBytes( Charset.forName( "UTF-8" ) ) )
            .build();

    AdvertiseCallback advertisingCallback = new AdvertiseCallback() {
        @Override
        public void onStartSuccess(AdvertiseSettings settingsInEffect) {
            Log.e( "BLE", "Advertising Started");
            super.onStartSuccess(settingsInEffect);
        }

        @Override
        public void onStartFailure(int errorCode) {
            Log.e( "BLE", "Advertising onStartFailure: " + errorCode );
            super.onStartFailure(errorCode);
        }
    };
    advertiser.startAdvertising( settings, data, advertisingCallback );
}

编辑：实际上，我注意到它与空闲无关。它实际上每次都在30秒标记时断开连接。

编辑：所以我添加了onCharacteristicRead和onCharacteristicWrite回调。但这似乎没有改变任何东西，这对我来说是有意义的，因为除了调用super.onCharacteristicRead()之外，我没有做任何事。另外，如果我不进行读写操作，那些就不会被调用。即使没有读取或写入请求，蓝牙也应该保持连接超过30秒。

private BluetoothGattServerCallback gattServerCallback = new BluetoothGattServerCallback() {
    @Override
    public void onConnectionStateChange(BluetoothDevice device, int status, int newState) {
        super.onConnectionStateChange(device, status, newState);
        if (newState == 2){
            connected_device = device;
            advertiser.stopAdvertising(new AdvertiseCallback() {});
        }
    }

    @Override
    public void onCharacteristicReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattCharacteristic characteristic) {
        super.onCharacteristicReadRequest(device, requestId, offset, characteristic);
    }

    @Override
    public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) {
        super.onCharacteristicWriteRequest(device, requestId, characteristic, preparedWrite, responseNeeded, offset, value);
    }

};

解

所以问题在于onCharacteristicReadRequest回调。 According to the docs：

应用程序必须调用BluetoothGattServer＃sendResponse来完成请求。

所以一旦我更新了我的回调，看起来像这样：

@Override
public void onCharacteristicReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattCharacteristic characteristic) {
    super.onCharacteristicReadRequest(device, requestId, offset, characteristic);
    gattServer.sendResponse(device, requestId, 1, offset, characteristic.getValue());
}

然后每隔几秒钟读取一次，然后就不会超时并断开连接。

Answer 1

根据ble core specification，ATT

未在30秒内完成的交易应超时。

在实践中，这通常表现为连接的一侧断开连接。

某些类型的GATT请求需要响应（即指示，读请求，写请求）。看起来你没有在你的Gatt服务器实现中实现onCharacteristicReadRequest和onCharacteristicWriteRequest等回调，这可能会导致这个问题。