Android example source code file (BluetoothSocket.java)

This example Android source code file (BluetoothSocket.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, bluetooth, bluetoothdevice, bluetoothinputstream, bluetoothoutputstream, bluetoothsocket, io, ioexception, max_rfcomm_channel, os, parceluuid, reentrantreadwritelock, remoteexception, rfcomm, sdphelper, service, string, type_rfcomm, util, utilities

The BluetoothSocket.java Android example source code

/*
 * Copyright (C) 2009 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.bluetooth.IBluetoothCallback;
import android.os.ParcelUuid;
import android.os.RemoteException;
import android.util.Log;

import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * A connected or connecting Bluetooth socket.
 *
 * <p>The interface for Bluetooth Sockets is similar to that of TCP sockets:
 * {@link java.net.Socket} and {@link java.net.ServerSocket}. On the server
 * side, use a {@link BluetoothServerSocket} to create a listening server
 * socket. When a connection is accepted by the {@link BluetoothServerSocket},
 * it will return a new {@link BluetoothSocket} to manage the connection.
 * On the client side, use a single {@link BluetoothSocket} to both intiate
 * an outgoing connection and to manage the connection.
 *
 * <p>The most common type of Bluetooth socket is RFCOMM, which is the type
 * supported by the Android APIs. RFCOMM is a connection-oriented, streaming
 * transport over Bluetooth. It is also known as the Serial Port Profile (SPP).
 *
 * <p>To create a {@link BluetoothSocket} for connecting to a known device, use
 * {@link BluetoothDevice#createRfcommSocketToServiceRecord
 * BluetoothDevice.createRfcommSocketToServiceRecord()}.
 * Then call {@link #connect()} to attempt a connection to the remote device.
 * This call will block until a connection is established or the connection
 * fails.
 *
 * <p>To create a {@link BluetoothSocket} as a server (or "host"), see the
 * {@link BluetoothServerSocket} documentation.
 *
 * <p>Once the socket is connected, whether initiated as a client or accepted
 * as a server, open the IO streams by calling {@link #getInputStream} and
 * {@link #getOutputStream} in order to retrieve {@link java.io.InputStream}
 * and {@link java.io.OutputStream} objects, respectively, which are
 * automatically connected to the socket.
 *
 * <p>{@link BluetoothSocket} is thread
 * safe. In particular, {@link #close} will always immediately abort ongoing
 * operations and close the socket.
 *
 * <p class="note">Note:
 * Requires the {@link android.Manifest.permission#BLUETOOTH} permission.
 *
 * {@see BluetoothServerSocket}
 * {@see java.io.InputStream}
 * {@see java.io.OutputStream}
 */
public final class BluetoothSocket implements Closeable {
    private static final String TAG = "BluetoothSocket";

    /** @hide */
    public static final int MAX_RFCOMM_CHANNEL = 30;

    /** Keep TYPE_ fields in sync with BluetoothSocket.cpp */
    /*package*/ static final int TYPE_RFCOMM = 1;
    /*package*/ static final int TYPE_SCO = 2;
    /*package*/ static final int TYPE_L2CAP = 3;

    /*package*/ static final int EBADFD = 77;
    /*package*/ static final int EADDRINUSE = 98;

    private final int mType;  /* one of TYPE_RFCOMM etc */
    private final BluetoothDevice mDevice;    /* remote device */
    private final String mAddress;    /* remote address */
    private final boolean mAuth;
    private final boolean mEncrypt;
    private final BluetoothInputStream mInputStream;
    private final BluetoothOutputStream mOutputStream;
    private final SdpHelper mSdp;

    private int mPort;  /* RFCOMM channel or L2CAP psm */

    /** prevents all native calls after destroyNative() */
    private boolean mClosed;

    /** protects mClosed */
    private final ReentrantReadWriteLock mLock;

    /** used by native code only */
    private int mSocketData;

    /**
     * Construct a BluetoothSocket.
     * @param type    type of socket
     * @param fd      fd to use for connected socket, or -1 for a new socket
     * @param auth    require the remote device to be authenticated
     * @param encrypt require the connection to be encrypted
     * @param device  remote device that this socket can connect to
     * @param port    remote port
     * @param uuid    SDP uuid
     * @throws IOException On error, for example Bluetooth not available, or
     *                     insufficient priveleges
     */
    /*package*/ BluetoothSocket(int type, int fd, boolean auth, boolean encrypt,
            BluetoothDevice device, int port, ParcelUuid uuid) throws IOException {
        if (type == BluetoothSocket.TYPE_RFCOMM && uuid == null && fd == -1) {
            if (port < 1 || port > MAX_RFCOMM_CHANNEL) {
                throw new IOException("Invalid RFCOMM channel: " + port);
            }
        }
        if (uuid == null) {
            mPort = port;
            mSdp = null;
        } else {
            mSdp = new SdpHelper(device, uuid);
            mPort = -1;
        }
        mType = type;
        mAuth = auth;
        mEncrypt = encrypt;
        mDevice = device;
        if (device == null) {
            mAddress = null;
        } else {
            mAddress = device.getAddress();
        }
        if (fd == -1) {
            initSocketNative();
        } else {
            initSocketFromFdNative(fd);
        }
        mInputStream = new BluetoothInputStream(this);
        mOutputStream = new BluetoothOutputStream(this);
        mClosed = false;
        mLock = new ReentrantReadWriteLock();
    }

    /**
     * Construct a BluetoothSocket from address. Used by native code.
     * @param type    type of socket
     * @param fd      fd to use for connected socket, or -1 for a new socket
     * @param auth    require the remote device to be authenticated
     * @param encrypt require the connection to be encrypted
     * @param address remote device that this socket can connect to
     * @param port    remote port
     * @throws IOException On error, for example Bluetooth not available, or
     *                     insufficient priveleges
     */
    private BluetoothSocket(int type, int fd, boolean auth, boolean encrypt, String address,
            int port) throws IOException {
        this(type, fd, auth, encrypt, new BluetoothDevice(address), port, null);
    }

    /** @hide */
    @Override
    protected void finalize() throws Throwable {
        try {
            close();
        } finally {
            super.finalize();
        }
    }

    /**
     * Attempt to connect to a remote device.
     * <p>This method will block until a connection is made or the connection
     * fails. If this method returns without an exception then this socket
     * is now connected.
     * <p>Creating new connections to
     * remote Bluetooth devices should not be attempted while device discovery
     * is in progress. Device discovery is a heavyweight procedure on the
     * Bluetooth adapter and will significantly slow a device connection.
     * Use {@link BluetoothAdapter#cancelDiscovery()} to cancel an ongoing
     * discovery. Discovery is not managed by the Activity,
     * but is run as a system service, so an application should always call
     * {@link BluetoothAdapter#cancelDiscovery()} even if it
     * did not directly request a discovery, just to be sure.
     * <p>{@link #close} can be used to abort this call from another thread.
     * @throws IOException on error, for example connection failure
     */
    public void connect() throws IOException {
        mLock.readLock().lock();
        try {
            if (mClosed) throw new IOException("socket closed");

            if (mSdp != null) {
                mPort = mSdp.doSdp();  // blocks
            }

            connectNative();  // blocks
        } finally {
            mLock.readLock().unlock();
        }
    }

    /**
     * Immediately close this socket, and release all associated resources.
     * <p>Causes blocked calls on this socket in other threads to immediately
     * throw an IOException.
     */
    public void close() throws IOException {
        // abort blocking operations on the socket
        mLock.readLock().lock();
        try {
            if (mClosed) return;
            if (mSdp != null) {
                mSdp.cancel();
            }
            abortNative();
        } finally {
            mLock.readLock().unlock();
        }

        // all native calls are guaranteed to immediately return after
        // abortNative(), so this lock should immediatley acquire
        mLock.writeLock().lock();
        try {
            mClosed = true;
            destroyNative();
        } finally {
            mLock.writeLock().unlock();
        }
    }

    /**
     * Get the remote device this socket is connecting, or connected, to.
     * @return remote device
     */
    public BluetoothDevice getRemoteDevice() {
        return mDevice;
    }

    /**
     * Get the input stream associated with this socket.
     * <p>The input stream will be returned even if the socket is not yet
     * connected, but operations on that stream will throw IOException until
     * the associated socket is connected.
     * @return InputStream
     */
    public InputStream getInputStream() throws IOException {
        return mInputStream;
    }

    /**
     * Get the output stream associated with this socket.
     * <p>The output stream will be returned even if the socket is not yet
     * connected, but operations on that stream will throw IOException until
     * the associated socket is connected.
     * @return OutputStream
     */
    public OutputStream getOutputStream() throws IOException {
        return mOutputStream;
    }

    /**
     * Currently returns unix errno instead of throwing IOException,
     * so that BluetoothAdapter can check the error code for EADDRINUSE
     */
    /*package*/ int bindListen() {
        mLock.readLock().lock();
        try {
            if (mClosed) return EBADFD;
            return bindListenNative();
        } finally {
            mLock.readLock().unlock();
        }
    }

    /*package*/ BluetoothSocket accept(int timeout) throws IOException {
        mLock.readLock().lock();
        try {
            if (mClosed) throw new IOException("socket closed");
            return acceptNative(timeout);
        } finally {
            mLock.readLock().unlock();
        }
    }

    /*package*/ int available() throws IOException {
        mLock.readLock().lock();
        try {
            if (mClosed) throw new IOException("socket closed");
            return availableNative();
        } finally {
            mLock.readLock().unlock();
        }
    }

    /*package*/ int read(byte[] b, int offset, int length) throws IOException {
        mLock.readLock().lock();
        try {
            if (mClosed) throw new IOException("socket closed");
            return readNative(b, offset, length);
        } finally {
            mLock.readLock().unlock();
        }
    }

    /*package*/ int write(byte[] b, int offset, int length) throws IOException {
        mLock.readLock().lock();
        try {
            if (mClosed) throw new IOException("socket closed");
            return writeNative(b, offset, length);
        } finally {
            mLock.readLock().unlock();
        }
    }

    private native void initSocketNative() throws IOException;
    private native void initSocketFromFdNative(int fd) throws IOException;
    private native void connectNative() throws IOException;
    private native int bindListenNative();
    private native BluetoothSocket acceptNative(int timeout) throws IOException;
    private native int availableNative() throws IOException;
    private native int readNative(byte[] b, int offset, int length) throws IOException;
    private native int writeNative(byte[] b, int offset, int length) throws IOException;
    private native void abortNative() throws IOException;
    private native void destroyNative() throws IOException;
    /**
     * Throws an IOException for given posix errno. Done natively so we can
     * use strerr to convert to string error.
     */
    /*package*/ native void throwErrnoNative(int errno) throws IOException;

    /**
     * Helper to perform blocking SDP lookup.
     */
    private static class SdpHelper extends IBluetoothCallback.Stub {
        private final IBluetooth service;
        private final ParcelUuid uuid;
        private final BluetoothDevice device;
        private int channel;
        private boolean canceled;
        public SdpHelper(BluetoothDevice device, ParcelUuid uuid) {
            service = BluetoothDevice.getService();
            this.device = device;
            this.uuid = uuid;
            canceled = false;
        }
        /**
         * Returns the RFCOMM channel for the UUID, or throws IOException
         * on failure.
         */
        public synchronized int doSdp() throws IOException {
            if (canceled) throw new IOException("Service discovery canceled");
            channel = -1;

            boolean inProgress = false;
            try {
                inProgress = service.fetchRemoteUuids(device.getAddress(), uuid, this);
            } catch (RemoteException e) {Log.e(TAG, "", e);}

            if (!inProgress) throw new IOException("Unable to start Service Discovery");

            try {
                /* 12 second timeout as a precaution - onRfcommChannelFound
                 * should always occur before the timeout */
                wait(12000);   // block

            } catch (InterruptedException e) {}

            if (canceled) throw new IOException("Service discovery canceled");
            if (channel < 1) throw new IOException("Service discovery failed");

            return channel;
        }
        /** Object cannot be re-used after calling cancel() */
        public synchronized void cancel() {
            if (!canceled) {
                canceled = true;
                channel = -1;
                notifyAll();  // unblock
            }
        }
        public synchronized void onRfcommChannelFound(int channel) {
            if (!canceled) {
                this.channel = channel;
                notifyAll();  // unblock
            }
        }
    }
}