core/java/android/bluetooth/BluetoothGatt.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.bluetooth;

import android.content.Context;
import android.os.ParcelUuid;
import android.os.RemoteException;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

/**
 * Public API for the Bluetooth GATT Profile.
 *
 * <p>This class provides Bluetooth GATT functionality to enable communication
 * with Bluetooth Smart or Smart Ready devices.
 *
 * <p>To connect to a remote peripheral device, create a {@link BluetoothGattCallback}
 * and call {@link BluetoothDevice#connectGatt} to get a instance of this class.
 * GATT capable devices can be discovered using the Bluetooth device discovery or BLE
 * scan process.
 */
public final class BluetoothGatt implements BluetoothProfile {
    private static final String TAG = "BluetoothGatt";
    private static final boolean DBG = true;
    private static final boolean VDBG = false;

    private final Context mContext;
    private IBluetoothGatt mService;
    private BluetoothGattCallback mCallback;
    private int mClientIf;
    private boolean mAuthRetry = false;
    private BluetoothDevice mDevice;
    private boolean mAutoConnect;
    private int mConnState;
    private final Object mStateLock = new Object();
    private Boolean mDeviceBusy = false;
    private int mTransport;

    private static final int CONN_STATE_IDLE = 0;
    private static final int CONN_STATE_CONNECTING = 1;
    private static final int CONN_STATE_CONNECTED = 2;
    private static final int CONN_STATE_DISCONNECTING = 3;
    private static final int CONN_STATE_CLOSED = 4;

    private List<BluetoothGattService> mServices;

    /** A GATT operation completed successfully */
    public static final int GATT_SUCCESS = 0;

    /** GATT read operation is not permitted */
    public static final int GATT_READ_NOT_PERMITTED = 0x2;

    /** GATT write operation is not permitted */
    public static final int GATT_WRITE_NOT_PERMITTED = 0x3;

    /** Insufficient authentication for a given operation */
    public static final int GATT_INSUFFICIENT_AUTHENTICATION = 0x5;

    /** The given request is not supported */
    public static final int GATT_REQUEST_NOT_SUPPORTED = 0x6;

    /** Insufficient encryption for a given operation */
    public static final int GATT_INSUFFICIENT_ENCRYPTION = 0xf;

    /** A read or write operation was requested with an invalid offset */
    public static final int GATT_INVALID_OFFSET = 0x7;

    /** A write operation exceeds the maximum length of the attribute */
    public static final int GATT_INVALID_ATTRIBUTE_LENGTH = 0xd;

    /** A remote device connection is congested. */
    public static final int GATT_CONNECTION_CONGESTED = 0x8f;

    /** A GATT operation failed, errors other than the above */
    public static final int GATT_FAILURE = 0x101;

    /**
     * Connection paramter update - Use the connection paramters recommended by the
     * Bluetooth SIG. This is the default value if no connection parameter update
     * is requested.
     */
    public static final int CONNECTION_PRIORITY_BALANCED = 0;

    /**
     * Connection paramter update - Request a high priority, low latency connection.
     * An application should only request high priority connection paramters to transfer
     * large amounts of data over LE quickly. Once the transfer is complete, the application
     * should request {@link BluetoothGatt#CONNECTION_PRIORITY_BALANCED} connectoin parameters
     * to reduce energy use.
     */
    public static final int CONNECTION_PRIORITY_HIGH = 1;

    /** Connection paramter update - Request low power, reduced data rate connection parameters. */
    public static final int CONNECTION_PRIORITY_LOW_POWER = 2;

    /**
     * No authentication required.
     * @hide
     */
    /*package*/ static final int AUTHENTICATION_NONE = 0;

    /**
     * Authentication requested; no man-in-the-middle protection required.
     * @hide
     */
    /*package*/ static final int AUTHENTICATION_NO_MITM = 1;

    /**
     * Authentication with man-in-the-middle protection requested.
     * @hide
     */
    /*package*/ static final int AUTHENTICATION_MITM = 2;

    /**
     * Bluetooth GATT callbacks. Overrides the default BluetoothGattCallback implementation.
     */
    private final IBluetoothGattCallback mBluetoothGattCallback =
        new BluetoothGattCallbackWrapper() {
            /**
             * Application interface registered - app is ready to go
             * @hide
             */
            public void onClientRegistered(int status, int clientIf) {
                if (DBG) Log.d(TAG, "onClientRegistered() - status=" + status
                    + " clientIf=" + clientIf);
                if (VDBG) {
                    synchronized(mStateLock) {
                        if (mConnState != CONN_STATE_CONNECTING) {
                            Log.e(TAG, "Bad connection state: " + mConnState);
                        }
                    }
                }
                mClientIf = clientIf;
                if (status != GATT_SUCCESS) {
                    mCallback.onConnectionStateChange(BluetoothGatt.this, GATT_FAILURE,
                                                      BluetoothProfile.STATE_DISCONNECTED);
                    synchronized(mStateLock) {
                        mConnState = CONN_STATE_IDLE;
                    }
                    return;
                }
                try {
                    mService.clientConnect(mClientIf, mDevice.getAddress(),
                                           !mAutoConnect, mTransport); // autoConnect is inverse of "isDirect"
                } catch (RemoteException e) {
                    Log.e(TAG,"",e);
                }
            }

            /**
             * Client connection state changed
             * @hide
             */
            public void onClientConnectionState(int status, int clientIf,
                                                boolean connected, String address) {
                if (DBG) Log.d(TAG, "onClientConnectionState() - status=" + status
                                 + " clientIf=" + clientIf + " device=" + address);
                if (!address.equals(mDevice.getAddress())) {
                    return;
                }
                int profileState = connected ? BluetoothProfile.STATE_CONNECTED :
                                               BluetoothProfile.STATE_DISCONNECTED;
                try {
                    mCallback.onConnectionStateChange(BluetoothGatt.this, status, profileState);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }

                synchronized(mStateLock) {
                    if (connected) {
                        mConnState = CONN_STATE_CONNECTED;
                    } else {
                        mConnState = CONN_STATE_IDLE;
                    }
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }
            }

            /**
             * Remote search has been completed.
             * The internal object structure should now reflect the state
             * of the remote device database. Let the application know that
             * we are done at this point.
             * @hide
             */
            public void onSearchComplete(String address, List<BluetoothGattService> services,
                                         int status) {
                if (DBG) Log.d(TAG, "onSearchComplete() = Device=" + address + " Status=" + status);
                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                for (BluetoothGattService s : services) {
                    //services we receive don't have device set properly.
                    s.setDevice(mDevice);
                }

                mServices.addAll(services);

                // Fix references to included services, as they doesn't point to right objects.
                for (BluetoothGattService fixedService : mServices) {
                    ArrayList<BluetoothGattService> includedServices =
                        new ArrayList(fixedService.getIncludedServices());
                    fixedService.getIncludedServices().clear();

                    for(BluetoothGattService brokenRef : includedServices) {
                        BluetoothGattService includedService = getService(mDevice,
                            brokenRef.getUuid(), brokenRef.getInstanceId(), brokenRef.getType());
                        if (includedService != null) {
                            fixedService.addIncludedService(includedService);
                        } else {
                            Log.e(TAG, "Broken GATT database: can't find included service.");
                        }
                    }
                }

                try {
                    mCallback.onServicesDiscovered(BluetoothGatt.this, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Remote characteristic has been read.
             * Updates the internal value.
             * @hide
             */
            public void onCharacteristicRead(String address, int status, int handle, byte[] value) {
                if (VDBG) Log.d(TAG, "onCharacteristicRead() - Device=" + address
                            + " handle=" + handle + " Status=" + status);

                 Log.w(TAG, "onCharacteristicRead() - Device=" + address
                            + " handle=" + handle + " Status=" + status);

                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }

                if ((status == GATT_INSUFFICIENT_AUTHENTICATION
                  || status == GATT_INSUFFICIENT_ENCRYPTION)
                  && mAuthRetry == false) {
                    try {
                        mAuthRetry = true;
                        mService.readCharacteristic(mClientIf, address, handle, AUTHENTICATION_MITM);
                        return;
                    } catch (RemoteException e) {
                        Log.e(TAG,"",e);
                    }
                }

                mAuthRetry = false;

                BluetoothGattCharacteristic characteristic = getCharacteristicById(mDevice, handle);
                if (characteristic == null) {
                    Log.w(TAG, "onCharacteristicRead() failed to find characteristic!");
                    return;
                }

                if (status == 0) characteristic.setValue(value);

                try {
                    mCallback.onCharacteristicRead(BluetoothGatt.this, characteristic, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Characteristic has been written to the remote device.
             * Let the app know how we did...
             * @hide
             */
            public void onCharacteristicWrite(String address, int status, int handle) {
                if (VDBG) Log.d(TAG, "onCharacteristicWrite() - Device=" + address
                            + " handle=" + handle + " Status=" + status);

                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }

                BluetoothGattCharacteristic characteristic = getCharacteristicById(mDevice, handle);
                if (characteristic == null) return;

                if ((status == GATT_INSUFFICIENT_AUTHENTICATION
                  || status == GATT_INSUFFICIENT_ENCRYPTION)
                  && mAuthRetry == false) {
                    try {
                        mAuthRetry = true;
                        mService.writeCharacteristic(mClientIf, address, handle,
                            characteristic.getWriteType(), AUTHENTICATION_MITM,
                            characteristic.getValue());
                        return;
                    } catch (RemoteException e) {
                        Log.e(TAG,"",e);
                    }
                }

                mAuthRetry = false;

                try {
                    mCallback.onCharacteristicWrite(BluetoothGatt.this, characteristic, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Remote characteristic has been updated.
             * Updates the internal value.
             * @hide
             */
            public void onNotify(String address, int handle, byte[] value) {
                if (VDBG) Log.d(TAG, "onNotify() - Device=" + address + " handle=" + handle);

                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                BluetoothGattCharacteristic characteristic = getCharacteristicById(mDevice, handle);
                if (characteristic == null) return;

                characteristic.setValue(value);

                try {
                    mCallback.onCharacteristicChanged(BluetoothGatt.this, characteristic);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Descriptor has been read.
             * @hide
             */
            public void onDescriptorRead(String address, int status, int handle, byte[] value) {
                if (VDBG) Log.d(TAG, "onDescriptorRead() - Device=" + address + " handle=" + handle);

                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }

                BluetoothGattDescriptor descriptor = getDescriptorById(mDevice, handle);
                if (descriptor == null) return;

                if (status == 0) descriptor.setValue(value);

                if ((status == GATT_INSUFFICIENT_AUTHENTICATION
                  || status == GATT_INSUFFICIENT_ENCRYPTION)
                  && mAuthRetry == false) {
                    try {
                        mAuthRetry = true;
                        mService.readDescriptor(mClientIf, address, handle, AUTHENTICATION_MITM);
                        return;
                    } catch (RemoteException e) {
                        Log.e(TAG,"",e);
                    }
                }

                mAuthRetry = true;

                try {
                    mCallback.onDescriptorRead(BluetoothGatt.this, descriptor, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Descriptor write operation complete.
             * @hide
             */
            public void onDescriptorWrite(String address, int status, int handle) {
                if (VDBG) Log.d(TAG, "onDescriptorWrite() - Device=" + address + " handle=" + handle);

                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }

                BluetoothGattDescriptor descriptor = getDescriptorById(mDevice, handle);
                if (descriptor == null) return;

                if ((status == GATT_INSUFFICIENT_AUTHENTICATION
                  || status == GATT_INSUFFICIENT_ENCRYPTION)
                  && mAuthRetry == false) {
                    try {
                        mAuthRetry = true;
                        mService.writeDescriptor(mClientIf, address, handle,
                            BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT,
                            AUTHENTICATION_MITM, descriptor.getValue());
                        return;
                    } catch (RemoteException e) {
                        Log.e(TAG,"",e);
                    }
                }

                mAuthRetry = false;

                try {
                    mCallback.onDescriptorWrite(BluetoothGatt.this, descriptor, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Prepared write transaction completed (or aborted)
             * @hide
             */
            public void onExecuteWrite(String address, int status) {
                if (VDBG) Log.d(TAG, "onExecuteWrite() - Device=" + address
                    + " status=" + status);
                if (!address.equals(mDevice.getAddress())) {
                    return;
                }

                synchronized(mDeviceBusy) {
                    mDeviceBusy = false;
                }

                try {
                    mCallback.onReliableWriteCompleted(BluetoothGatt.this, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Remote device RSSI has been read
             * @hide
             */
            public void onReadRemoteRssi(String address, int rssi, int status) {
                if (VDBG) Log.d(TAG, "onReadRemoteRssi() - Device=" + address +
                            " rssi=" + rssi + " status=" + status);
                if (!address.equals(mDevice.getAddress())) {
                    return;
                }
                try {
                    mCallback.onReadRemoteRssi(BluetoothGatt.this, rssi, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }

            /**
             * Callback invoked when the MTU for a given connection changes
             * @hide
             */
            public void onConfigureMTU(String address, int mtu, int status) {
                if (DBG) Log.d(TAG, "onConfigureMTU() - Device=" + address +
                            " mtu=" + mtu + " status=" + status);
                if (!address.equals(mDevice.getAddress())) {
                    return;
                }
                try {
                    mCallback.onMtuChanged(BluetoothGatt.this, mtu, status);
                } catch (Exception ex) {
                    Log.w(TAG, "Unhandled exception in callback", ex);
                }
            }
        };

    /*package*/ BluetoothGatt(Context context, IBluetoothGatt iGatt, BluetoothDevice device,
                                int transport) {
        mContext = context;
        mService = iGatt;
        mDevice = device;
        mTransport = transport;
        mServices = new ArrayList<BluetoothGattService>();

        mConnState = CONN_STATE_IDLE;
    }

    /**
     * Close this Bluetooth GATT client.
     *
     * Application should call this method as early as possible after it is done with
     * this GATT client.
     */
    public void close() {
        if (DBG) Log.d(TAG, "close()");

        unregisterApp();
        mConnState = CONN_STATE_CLOSED;
    }

    /**
     * Returns a service by UUID, instance and type.
     * @hide
     */
    /*package*/ BluetoothGattService getService(BluetoothDevice device, UUID uuid,
                                                int instanceId, int type) {
        for(BluetoothGattService svc : mServices) {
            if (svc.getDevice().equals(device) &&
                svc.getType() == type &&
                svc.getInstanceId() == instanceId &&
                svc.getUuid().equals(uuid)) {
                return svc;
            }
        }
        return null;
    }


    /**
     * Returns a characteristic with id equal to instanceId.
     * @hide
     */
    /*package*/ BluetoothGattCharacteristic getCharacteristicById(BluetoothDevice device, int instanceId) {
        for(BluetoothGattService svc : mServices) {
            for(BluetoothGattCharacteristic charac : svc.getCharacteristics()) {
                if (charac.getInstanceId() == instanceId)
                    return charac;
            }
        }
        return null;
    }

    /**
     * Returns a descriptor with id equal to instanceId.
     * @hide
     */
    /*package*/ BluetoothGattDescriptor getDescriptorById(BluetoothDevice device, int instanceId) {
        for(BluetoothGattService svc : mServices) {
            for(BluetoothGattCharacteristic charac : svc.getCharacteristics()) {
                for(BluetoothGattDescriptor desc : charac.getDescriptors()) {
                    if (desc.getInstanceId() == instanceId)
                        return desc;
                }
            }
        }
        return null;
    }

    /**
     * Register an application callback to start using GATT.
     *
     * <p>This is an asynchronous call. The callback {@link BluetoothGattCallback#onAppRegistered}
     * is used to notify success or failure if the function returns true.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param callback GATT callback handler that will receive asynchronous callbacks.
     * @return If true, the callback will be called to notify success or failure,
     *         false on immediate error
     */
    private boolean registerApp(BluetoothGattCallback callback) {
        if (DBG) Log.d(TAG, "registerApp()");
        if (mService == null) return false;

        mCallback = callback;
        UUID uuid = UUID.randomUUID();
        if (DBG) Log.d(TAG, "registerApp() - UUID=" + uuid);

        try {
            mService.registerClient(new ParcelUuid(uuid), mBluetoothGattCallback);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Unregister the current application and callbacks.
     */
    private void unregisterApp() {
        if (DBG) Log.d(TAG, "unregisterApp() - mClientIf=" + mClientIf);
        if (mService == null || mClientIf == 0) return;

        try {
            mCallback = null;
            mService.unregisterClient(mClientIf);
            mClientIf = 0;
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
        }
    }

    /**
     * Initiate a connection to a Bluetooth GATT capable device.
     *
     * <p>The connection may not be established right away, but will be
     * completed when the remote device is available. A
     * {@link BluetoothGattCallback#onConnectionStateChange} callback will be
     * invoked when the connection state changes as a result of this function.
     *
     * <p>The autoConnect parameter determines whether to actively connect to
     * the remote device, or rather passively scan and finalize the connection
     * when the remote device is in range/available. Generally, the first ever
     * connection to a device should be direct (autoConnect set to false) and
     * subsequent connections to known devices should be invoked with the
     * autoConnect parameter set to true.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param device Remote device to connect to
     * @param autoConnect Whether to directly connect to the remote device (false)
     *                    or to automatically connect as soon as the remote
     *                    device becomes available (true).
     * @return true, if the connection attempt was initiated successfully
     */
    /*package*/ boolean connect(Boolean autoConnect, BluetoothGattCallback callback) {
        if (DBG) Log.d(TAG, "connect() - device: " + mDevice.getAddress() + ", auto: " + autoConnect);
        synchronized(mStateLock) {
            if (mConnState != CONN_STATE_IDLE) {
                throw new IllegalStateException("Not idle");
            }
            mConnState = CONN_STATE_CONNECTING;
        }
        if (!registerApp(callback)) {
            synchronized(mStateLock) {
                mConnState = CONN_STATE_IDLE;
            }
            Log.e(TAG, "Failed to register callback");
            return false;
        }

        // the connection will continue after successful callback registration
        mAutoConnect = autoConnect;
        return true;
    }

    /**
     * Disconnects an established connection, or cancels a connection attempt
     * currently in progress.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     */
    public void disconnect() {
        if (DBG) Log.d(TAG, "cancelOpen() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return;

        try {
            mService.clientDisconnect(mClientIf, mDevice.getAddress());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
        }
    }

    /**
     * Connect back to remote device.
     *
     * <p>This method is used to re-connect to a remote device after the
     * connection has been dropped. If the device is not in range, the
     * re-connection will be triggered once the device is back in range.
     *
     * @return true, if the connection attempt was initiated successfully
     */
    public boolean connect() {
        try {
            mService.clientConnect(mClientIf, mDevice.getAddress(),
                                   false, mTransport); // autoConnect is inverse of "isDirect"
            return true;
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }
    }

    /**
     * Return the remote bluetooth device this GATT client targets to
     *
     * @return remote bluetooth device
     */
    public BluetoothDevice getDevice() {
        return mDevice;
    }

    /**
     * Discovers services offered by a remote device as well as their
     * characteristics and descriptors.
     *
     * <p>This is an asynchronous operation. Once service discovery is completed,
     * the {@link BluetoothGattCallback#onServicesDiscovered} callback is
     * triggered. If the discovery was successful, the remote services can be
     * retrieved using the {@link #getServices} function.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return true, if the remote service discovery has been started
     */
    public boolean discoverServices() {
        if (DBG) Log.d(TAG, "discoverServices() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return false;

        mServices.clear();

        try {
            mService.discoverServices(mClientIf, mDevice.getAddress());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Returns a list of GATT services offered by the remote device.
     *
     * <p>This function requires that service discovery has been completed
     * for the given device.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return List of services on the remote device. Returns an empty list
     *         if service discovery has not yet been performed.
     */
    public List<BluetoothGattService> getServices() {
        List<BluetoothGattService> result =
                new ArrayList<BluetoothGattService>();

        for (BluetoothGattService service : mServices) {
            if (service.getDevice().equals(mDevice)) {
                result.add(service);
            }
        }

        return result;
    }

    /**
     * Returns a {@link BluetoothGattService}, if the requested UUID is
     * supported by the remote device.
     *
     * <p>This function requires that service discovery has been completed
     * for the given device.
     *
     * <p>If multiple instances of the same service (as identified by UUID)
     * exist, the first instance of the service is returned.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param uuid UUID of the requested service
     * @return BluetoothGattService if supported, or null if the requested
     *         service is not offered by the remote device.
     */
    public BluetoothGattService getService(UUID uuid) {
        for (BluetoothGattService service : mServices) {
            if (service.getDevice().equals(mDevice) &&
                service.getUuid().equals(uuid)) {
                return service;
            }
        }

        return null;
    }

    /**
     * Reads the requested characteristic from the associated remote device.
     *
     * <p>This is an asynchronous operation. The result of the read operation
     * is reported by the {@link BluetoothGattCallback#onCharacteristicRead}
     * callback.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param characteristic Characteristic to read from the remote device
     * @return true, if the read operation was initiated successfully
     */
    public boolean readCharacteristic(BluetoothGattCharacteristic characteristic) {
        if ((characteristic.getProperties() &
                BluetoothGattCharacteristic.PROPERTY_READ) == 0) return false;

        if (VDBG) Log.d(TAG, "readCharacteristic() - uuid: " + characteristic.getUuid());
        if (mService == null || mClientIf == 0) return false;

        BluetoothGattService service = characteristic.getService();
        if (service == null) return false;

        BluetoothDevice device = service.getDevice();
        if (device == null) return false;

        synchronized(mDeviceBusy) {
            if (mDeviceBusy) return false;
            mDeviceBusy = true;
        }

        try {
            mService.readCharacteristic(mClientIf, device.getAddress(),
                characteristic.getInstanceId(), AUTHENTICATION_NONE);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            mDeviceBusy = false;
            return false;
        }

        return true;
    }

    /**
     * Writes a given characteristic and its values to the associated remote device.
     *
     * <p>Once the write operation has been completed, the
     * {@link BluetoothGattCallback#onCharacteristicWrite} callback is invoked,
     * reporting the result of the operation.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param characteristic Characteristic to write on the remote device
     * @return true, if the write operation was initiated successfully
     */
    public boolean writeCharacteristic(BluetoothGattCharacteristic characteristic) {
        if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_WRITE) == 0
            && (characteristic.getProperties() &
                BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE) == 0) return false;

        if (VDBG) Log.d(TAG, "writeCharacteristic() - uuid: " + characteristic.getUuid());
        if (mService == null || mClientIf == 0 || characteristic.getValue() == null) return false;

        BluetoothGattService service = characteristic.getService();
        if (service == null) return false;

        BluetoothDevice device = service.getDevice();
        if (device == null) return false;

        synchronized(mDeviceBusy) {
            if (mDeviceBusy) return false;
            mDeviceBusy = true;
        }

        try {
            mService.writeCharacteristic(mClientIf, device.getAddress(),
                characteristic.getInstanceId(), characteristic.getWriteType(),
                AUTHENTICATION_NONE, characteristic.getValue());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            mDeviceBusy = false;
            return false;
        }

        return true;
    }

    /**
     * Reads the value for a given descriptor from the associated remote device.
     *
     * <p>Once the read operation has been completed, the
     * {@link BluetoothGattCallback#onDescriptorRead} callback is
     * triggered, signaling the result of the operation.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param descriptor Descriptor value to read from the remote device
     * @return true, if the read operation was initiated successfully
     */
    public boolean readDescriptor(BluetoothGattDescriptor descriptor) {
        if (VDBG) Log.d(TAG, "readDescriptor() - uuid: " + descriptor.getUuid());
        if (mService == null || mClientIf == 0) return false;

        BluetoothGattCharacteristic characteristic = descriptor.getCharacteristic();
        if (characteristic == null) return false;

        BluetoothGattService service = characteristic.getService();
        if (service == null) return false;

        BluetoothDevice device = service.getDevice();
        if (device == null) return false;

        synchronized(mDeviceBusy) {
            if (mDeviceBusy) return false;
            mDeviceBusy = true;
        }

        try {
            mService.readDescriptor(mClientIf, device.getAddress(),
                descriptor.getInstanceId(), AUTHENTICATION_NONE);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            mDeviceBusy = false;
            return false;
        }

        return true;
    }

    /**
     * Write the value of a given descriptor to the associated remote device.
     *
     * <p>A {@link BluetoothGattCallback#onDescriptorWrite} callback is
     * triggered to report the result of the write operation.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param descriptor Descriptor to write to the associated remote device
     * @return true, if the write operation was initiated successfully
     */
    public boolean writeDescriptor(BluetoothGattDescriptor descriptor) {
        if (VDBG) Log.d(TAG, "writeDescriptor() - uuid: " + descriptor.getUuid());
        if (mService == null || mClientIf == 0 || descriptor.getValue() == null) return false;

        BluetoothGattCharacteristic characteristic = descriptor.getCharacteristic();
        if (characteristic == null) return false;

        BluetoothGattService service = characteristic.getService();
        if (service == null) return false;

        BluetoothDevice device = service.getDevice();
        if (device == null) return false;

        synchronized(mDeviceBusy) {
            if (mDeviceBusy) return false;
            mDeviceBusy = true;
        }

        try {
            mService.writeDescriptor(mClientIf, device.getAddress(), descriptor.getInstanceId(),
                BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT, AUTHENTICATION_NONE,
                descriptor.getValue());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            mDeviceBusy = false;
            return false;
        }

        return true;
    }

    /**
     * Initiates a reliable write transaction for a given remote device.
     *
     * <p>Once a reliable write transaction has been initiated, all calls
     * to {@link #writeCharacteristic} are sent to the remote device for
     * verification and queued up for atomic execution. The application will
     * receive an {@link BluetoothGattCallback#onCharacteristicWrite} callback
     * in response to every {@link #writeCharacteristic} call and is responsible
     * for verifying if the value has been transmitted accurately.
     *
     * <p>After all characteristics have been queued up and verified,
     * {@link #executeReliableWrite} will execute all writes. If a characteristic
     * was not written correctly, calling {@link #abortReliableWrite} will
     * cancel the current transaction without commiting any values on the
     * remote device.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return true, if the reliable write transaction has been initiated
     */
    public boolean beginReliableWrite() {
        if (VDBG) Log.d(TAG, "beginReliableWrite() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return false;

        try {
            mService.beginReliableWrite(mClientIf, mDevice.getAddress());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Executes a reliable write transaction for a given remote device.
     *
     * <p>This function will commit all queued up characteristic write
     * operations for a given remote device.
     *
     * <p>A {@link BluetoothGattCallback#onReliableWriteCompleted} callback is
     * invoked to indicate whether the transaction has been executed correctly.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return true, if the request to execute the transaction has been sent
     */
    public boolean executeReliableWrite() {
        if (VDBG) Log.d(TAG, "executeReliableWrite() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return false;

        synchronized(mDeviceBusy) {
            if (mDeviceBusy) return false;
            mDeviceBusy = true;
        }

        try {
            mService.endReliableWrite(mClientIf, mDevice.getAddress(), true);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            mDeviceBusy = false;
            return false;
        }

        return true;
    }

    /**
     * Cancels a reliable write transaction for a given device.
     *
     * <p>Calling this function will discard all queued characteristic write
     * operations for a given remote device.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     */
    public void abortReliableWrite() {
        if (VDBG) Log.d(TAG, "abortReliableWrite() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return;

        try {
            mService.endReliableWrite(mClientIf, mDevice.getAddress(), false);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
        }
    }

    /**
     * @deprecated Use {@link #abortReliableWrite()}
     */
    public void abortReliableWrite(BluetoothDevice mDevice) {
        abortReliableWrite();
    }

    /**
     * Enable or disable notifications/indications for a given characteristic.
     *
     * <p>Once notifications are enabled for a characteristic, a
     * {@link BluetoothGattCallback#onCharacteristicChanged} callback will be
     * triggered if the remote device indicates that the given characteristic
     * has changed.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param characteristic The characteristic for which to enable notifications
     * @param enable Set to true to enable notifications/indications
     * @return true, if the requested notification status was set successfully
     */
    public boolean setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
                                              boolean enable) {
        if (DBG) Log.d(TAG, "setCharacteristicNotification() - uuid: " + characteristic.getUuid()
                         + " enable: " + enable);
        if (mService == null || mClientIf == 0) return false;

        BluetoothGattService service = characteristic.getService();
        if (service == null) return false;

        BluetoothDevice device = service.getDevice();
        if (device == null) return false;

        try {
            mService.registerForNotification(mClientIf, device.getAddress(),
                characteristic.getInstanceId(), enable);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Clears the internal cache and forces a refresh of the services from the
     * remote device.
     * @hide
     */
    public boolean refresh() {
        if (DBG) Log.d(TAG, "refresh() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return false;

        try {
            mService.refreshDevice(mClientIf, mDevice.getAddress());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Read the RSSI for a connected remote device.
     *
     * <p>The {@link BluetoothGattCallback#onReadRemoteRssi} callback will be
     * invoked when the RSSI value has been read.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return true, if the RSSI value has been requested successfully
     */
    public boolean readRemoteRssi() {
        if (DBG) Log.d(TAG, "readRssi() - device: " + mDevice.getAddress());
        if (mService == null || mClientIf == 0) return false;

        try {
            mService.readRemoteRssi(mClientIf, mDevice.getAddress());
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Request an MTU size used for a given connection.
     *
     * <p>When performing a write request operation (write without response),
     * the data sent is truncated to the MTU size. This function may be used
     * to request a larger MTU size to be able to send more data at once.
     *
     * <p>A {@link BluetoothGattCallback#onMtuChanged} callback will indicate
     * whether this operation was successful.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return true, if the new MTU value has been requested successfully
     */
    public boolean requestMtu(int mtu) {
        if (DBG) Log.d(TAG, "configureMTU() - device: " + mDevice.getAddress()
                            + " mtu: " + mtu);
        if (mService == null || mClientIf == 0) return false;

        try {
            mService.configureMTU(mClientIf, mDevice.getAddress(), mtu);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Request a connection parameter update.
     *
     * <p>This function will send a connection parameter update request to the
     * remote device.
     *
     * @param connectionPriority Request a specific connection priority. Must be one of
     *          {@link BluetoothGatt#CONNECTION_PRIORITY_BALANCED},
     *          {@link BluetoothGatt#CONNECTION_PRIORITY_HIGH}
     *          or {@link BluetoothGatt#CONNECTION_PRIORITY_LOW_POWER}.
     * @throws IllegalArgumentException If the parameters are outside of their
     *                                  specified range.
     */
    public boolean requestConnectionPriority(int connectionPriority) {
        if (connectionPriority < CONNECTION_PRIORITY_BALANCED ||
            connectionPriority > CONNECTION_PRIORITY_LOW_POWER) {
            throw new IllegalArgumentException("connectionPriority not within valid range");
        }

        if (DBG) Log.d(TAG, "requestConnectionPriority() - params: " + connectionPriority);
        if (mService == null || mClientIf == 0) return false;

        try {
            mService.connectionParameterUpdate(mClientIf, mDevice.getAddress(), connectionPriority);
        } catch (RemoteException e) {
            Log.e(TAG,"",e);
            return false;
        }

        return true;
    }

    /**
     * Not supported - please use {@link BluetoothManager#getConnectedDevices(int)}
     * with {@link BluetoothProfile#GATT} as argument
     *
     * @throws UnsupportedOperationException
     */
    @Override
    public int getConnectionState(BluetoothDevice device) {
        throw new UnsupportedOperationException("Use BluetoothManager#getConnectionState instead.");
    }

    /**
     * Not supported - please use {@link BluetoothManager#getConnectedDevices(int)}
     * with {@link BluetoothProfile#GATT} as argument
     *
     * @throws UnsupportedOperationException
     */
    @Override
    public List<BluetoothDevice> getConnectedDevices() {
        throw new UnsupportedOperationException
            ("Use BluetoothManager#getConnectedDevices instead.");
    }

    /**
     * Not supported - please use
     * {@link BluetoothManager#getDevicesMatchingConnectionStates(int, int[])}
     * with {@link BluetoothProfile#GATT} as first argument
     *
     * @throws UnsupportedOperationException
     */
    @Override
    public List<BluetoothDevice> getDevicesMatchingConnectionStates(int[] states) {
        throw new UnsupportedOperationException
            ("Use BluetoothManager#getDevicesMatchingConnectionStates instead.");
    }
}