是的，BLE服务可以实现外设和服务器之间的双向写入。在设置BLE服务时，设置相应的属性即可实现双向写入。

以下是在Android设备上实现双向写入的示例代码：

在外设端：

//创建BluetoothGattCharacteristic对象，同时设置读写属性和回调函数 BluetoothGattCharacteristic myReadWriteCharacteristic = new BluetoothGattCharacteristic(UUID.fromString("your_readwrite_char_uuid"), BluetoothGattCharacteristic.PROPERTY_READ | BluetoothGattCharacteristic.PROPERTY_WRITE, BluetoothGattCharacteristic.PERMISSION_READ | BluetoothGattCharacteristic.PERMISSION_WRITE);

//添加Characteristic到Service中 BluetoothGattService myService = new BluetoothGattService(UUID.fromString("your_service_uuid"), BluetoothGattService.SERVICE_TYPE_PRIMARY); myService.addCharacteristic(myReadWriteCharacteristic);

//启动peripheral的BLE advertisement bluetoothLeAdvertiser = bluetoothAdapter.getBluetoothLeAdvertiser(); AdvertiseSettings settings = new AdvertiseSettings.Builder().setAdvertiseMode(AdvertiseSettings.ADVERTISE_MODE_BALANCED).setConnectable(true).setTimeout(0).setTxPowerLevel(AdvertiseSettings.ADVERTISE_TX_POWER_HIGH).build(); AdvertiseData data = new AdvertiseData.Builder().setIncludeTxPowerLevel(true).setIncludeDeviceName(true).build(); bluetoothLeAdvertiser.startAdvertising(settings, data, advertiseCallback);

//在Peripheral端的回调函数中处理双向写入 @Override public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) { if (characteristic.getUuid().equals(UUID.fromString("your_readwrite_char_uuid"))) { //获取写入的数据 String data = new String(value); Log.d(TAG, "onCharacteristicWriteRequest: data written - " + data);

    //处理写入的数据
    //此处可以回复写入状态给Central端，如果responseNeeded为true
    if (responseNeeded) {
        bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);
    }
}

}

在服务器端：

//连接到Peripheral端 bluetoothGatt = bluetoothDevice.connectGatt(this, false, gattCallback);

//获取Peripheral端的Service和Characteristic BluetoothGattService myService = bluetoothGatt.getService(UUID.fromString("your_service_uuid")); BluetoothGattCharacteristic myReadWriteCharacteristic = myService.getCharacteristic(UUID.fromString("your_readwrite_char_uuid"));

//写入数据到Peripheral端的Characteristic byte[] data = "Hello Peripheral!".getBytes(); myReadWriteCharacteristic.setValue(data); bluetoothGatt.writeCharacteristic(myReadWriteCharacteristic);

//在Central端的回调函数中处理Peripheral端的回复