Question

我一直在尝试弄清楚如何让这些手机通过蓝牙相互通话。我已将Android手机设置为外围设备，并且我的iPhone正在运行nrf connect app。我可以通过iPhone进行广告宣传并连接到Android手机，并且可以订阅通知并查看更新的特性。问题是，如果我没有发送特征通知，则大约7-10秒后，连接将会丢失。我在connectionStateChanged回调处理程序上得到了一个回调，但我不知道是什么原因造成的。我不认为这是nrf应用程序，因为我已经连接到其他东西，并且它永远保持连接状态。有什么我想念的吗？

以下是一些代码：

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，我注意到这与空闲无关。实际上，每次30秒时，它几乎断开连接。

编辑：因此，我添加了onCharacteristicRead和onCharacteristicWrite回调。但这似乎并没有改变任何东西，这对我来说很有意义，因为除了调用super.onCharacteristicRead()之外，我没有对它们做任何事情。另外，如果我不进行读写操作，则不会调用这些方法。而且，即使没有读取或写入请求，蓝牙也应该保持连接30秒以上。

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);
    }

};

解决方案

因此问题出在onCharacteristicReadRequest回调中。 According to the docs：

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

因此，一旦我将回调更新为以下形式：

@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，那么它不会超时并断开连接。

Answer 1

根据ble core specification，对于ATT

30秒内未完成的交易将超时。

实际上，这通常表现为连接一侧的断开连接。

某些类型的GATT请求需要响应（即指示，读取请求，写入请求）。看起来您在Gatt服务器实现中未实现onCharacteristicReadRequest和onCharacteristicWriteRequest之类的回调，这可能会导致此问题。

BluetoothGattServer始终在30秒后断开连接

解决方案

1 个答案: