蓝牙的野史：

蓝牙的名字来源于10世纪丹麦国王Harald Blatand，英文名字是Harald Bluetooth，没错，这个蓝牙就是那个蓝牙。因为这个国王将挪威、瑞典和丹麦统一起来，这就像这项技术把无线通信统一起来一样，所以，无线行业协会组织人员讨论后，就用这个名字命名了。

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蓝牙的协议：

蓝牙的协议分为4层：

       核心协议层、 电缆替代协议层、 电话控制协议层、  其他协议层  

       

       其中，核心协议层是最重要的部分。包括基带、链路管理、逻辑链路控制和适应协议四部分。其中链路管理（LMP）负责蓝牙组件间的连接的建立。 逻辑链路控制和适应协议（L2CAP）位于基带协议层之上，属于数据链路层，是一个为高层传输和应用层协议屏蔽基带协议的适配协议。

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打开和关闭蓝牙设备：

第一种方式：

Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent,1);

会出现一个窗口请求权限供用户选择是否打开。

第二种方式：

必须设置权限：

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

然后代码实现：

BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
//调用enable就把蓝牙打开
adapter.enable();
//调用disable就把蓝牙关闭
adapter.disable();

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蓝牙数据传输：

通过蓝牙传输数据与Socket类似。在网络中使用Socket和ServerSocket控制客户端和服务端的数据读写。而蓝牙通讯也由客户端和服务端Socket来完成。蓝牙客户端Socket是BluetoothSocket，蓝牙服务端Socket是BluetoothServerSocket。这两个类都在android.bluetooth包中。

无论是BluetoothSocket,还是 BluetoothSocket，都需要一个UUID（全局唯一标识符，Universally Unique Identifier）。

格式如下：xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

UUID的格式被分成5段，形成一个8-4-4-4-12的字符串。

例子：在两个Android设备中传输数据。

先完成蓝牙的搜索功能，并连接另一部设备，再在两部设备中传输数据

package com.sadaharu.jacksom.bluetooth;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.UUID;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener{private BluetoothAdapter mBluetoothAdapter;
    private ListView lvDevices;

    private List<String> bluetoothDevices = new ArrayList<>();

    private ArrayAdapter<String> arrayAdapter;

    private final UUID MY_UUID = UUID.randomUUID();
    private final String NAME = "Bluetooth_Socket";

    private BluetoothSocket clientSocket;
    private BluetoothDevice device;
    private AcceptThread acceptThread;
    private OutputStream os;

    @Override
    protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

      /*//蓝牙的打开方式一：
        Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(intent,1);

        //蓝牙的打开方式二：
        BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
        //调用enable就把蓝牙打开
        adapter.enable();
        //调用disable就把蓝牙关闭
        adapter.disable();*/

        lvDevices = (ListView) findViewById(R.id.lvDevices);
        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        acceptThread = new AcceptThread();
        acceptThread.start();

        //已经配过对的，存储在这个集合里
        Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();

        //将已经配对过的设备显示出来
        if (pairedDevices.size() > 0){for (BluetoothDevice device : pairedDevices){bluetoothDevices.add(device.getName() + ":" + device.getAddress());
            }}arrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,
                android.R.id.text1,bluetoothDevices);

        lvDevices.setAdapter(arrayAdapter);
        lvDevices.setOnItemClickListener(this);

        //找到一个设备会发送广播
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        this.registerReceiver(receiver, filter);

        //全部搜索完成会发送一个广播
        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.registerReceiver(receiver, filter);
    }//按钮监听方法
    public void onClick_Search(View view){//设置一个进度条显示正在扫描
        setProgressBarVisibility(true);
        setTitle("正在扫描……");
        if (mBluetoothAdapter.isDiscovering()){mBluetoothAdapter.cancelDiscovery();
        }mBluetoothAdapter.startDiscovery();
    }private final BroadcastReceiver receiver = new BroadcastReceiver() {@Override
        public void onReceive(Context context, Intent intent) {String action = intent.getAction();
            //如果找到这个设备
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {//获得这个设备的信息
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                //如果没有被配对过，再添加
                if (device.getBondState() != BluetoothDevice.BOND_BONDED){bluetoothDevices.add(device.getName() + ":" + device.getAddress() + "\n");
                    arrayAdapter.notifyDataSetChanged();
                }}else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)){setProgressBarVisibility(false);
                setTitle("搜索已经完成");
            }}};

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {String s = arrayAdapter.getItem(position);
        String address = s.substring(s.indexOf(":") + 1).trim();

        try{if (mBluetoothAdapter.isDiscovering()){mBluetoothAdapter.cancelDiscovery();
            }if (device == null){device = mBluetoothAdapter.getRemoteDevice(address);
            }if (clientSocket == null){clientSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
                clientSocket.connect();

                os = clientSocket.getOutputStream();
            }}catch (Exception e ){}if (os != null){try {os.write("发送信息到其他蓝牙设备".getBytes("utf-8"));
            } catch (IOException e) {e.printStackTrace();
            }}}//服务端
    private Handler handler = new Handler(){public void handlerMessage(Message msg){Toast.makeText(MainActivity.this,String.valueOf(msg.obj),Toast.LENGTH_LONG).show();
            super.handleMessage(msg);
        }};

    private class AcceptThread extends Thread{private BluetoothServerSocket serverSocket;
        private BluetoothSocket socket;
        private InputStream is;
        private OutputStream os;
        public AcceptThread(){try {serverSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME,MY_UUID);
            } catch (IOException e) {e.printStackTrace();
            }}@Override
        public void run() {try {socket = serverSocket.accept();
                is = socket.getInputStream();
                os = socket.getOutputStream();

                //有数据就从客户端读入，没有数据就阻塞
                while (true){byte[] buffer = new byte[128];
                    int count = is.read(buffer);
                    Message msg = new Message();
                    msg.obj = new String(buffer, 0,count,"utf-8");
                    handler.sendMessage(msg);
                }} catch (IOException e) {e.printStackTrace();
            }}}
}

例子代码的地址：

github：https://github.com/sadaharusong/Bluetooth/