上一篇文章介绍了蓝牙的技术知识，这里我们具体说明一下中心模式的应用场景。主设备（手机去扫描连接外设，发现外设服务和属性，操作服务和属性的应用。一般来说，外设（蓝牙设备，比如智能手环之类的东西），会由硬件工程师开发好，并定义好设备提供的服务，每个服务对于的特征，每个特征的属性（只读，只写，通知等等），本文例子的业务场景，就是用一手机app去读写蓝牙设备。

【iOS 蓝牙开发（二）iOS 连接外设的代码实现】 iOS连接外设的代码实现流程
1. 建立中心角色
2. 扫描外设（discover）
3. 连接外设(connect)
4. 扫描外设中的服务和特征(discover)
? ? - 4.1 获取外设的services
? ? - 4.2 获取外设的Characteristics,获取Characteristics的值，获取Characteristics的Descriptor和Descriptor的值
5. 与外设做数据交互(explore and interact)
6. 订阅Characteristic的通知
7. 断开连接(disconnect)
准备环境
? 1 Xcode
? 2 开发证书和手机（蓝牙程序需要使用使用真机调试，使用模拟器也可以调试，但是方法很蛋疼，我会放在最后说）
? 3 蓝牙外设
实现步骤
1 导入CoreBluetooth头文件，建立主设备管理类，设置主设备委托

????#import? ????@interface?ViewController?:?UIViewController ????@interface?ViewController?(){ ????????//系统蓝牙设备管理对象，可以把他理解为主设备，通过他，可以去扫描和链接外设 ????????CBCentralManager?*manager; ????} ????-?(void)viewDidLoad?{ ????????[super?viewDidLoad]; ????????/* ?????????设置主设备的委托,CBCentralManagerDelegate ????????????必须实现的： ????????????-?(void)centralManagerDidUpdateState:(CBCentralManager?*)central; //主设备状态改变的委托，在初始化CBCentralManager的适合会打开设备，只有当设备正确打开后才能使用 ????????????其他选择实现的委托中比较重要的： ????????????-?(void)centralManager:(CBCentralManager?*)central?didDiscoverPeripheral:(CBPeripheral?*)peripheral?advertisementData:(NSDictionary?*)advertisementData?RSSI:(NSNumber?*)RSSI; ?//找到外设的委托 ????????????-?(void)centralManager:(CBCentralManager?*)central?didConnectPeripheral:(CBPeripheral?*)peripheral; //连接外设成功的委托 ????????????-?(void)centralManager:(CBCentralManager?*)central?didFailToConnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error; //外设连接失败的委托 ????????????-?(void)centralManager:(CBCentralManager?*)central?didDisconnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error; //断开外设的委托 ????????*/ ?????????//初始化并设置委托和线程队列，最好一个线程的参数可以为nil，默认会就main线程 ?????????manager?=?[[CBCentralManager?alloc]initWithDelegate:self?queue:dispatch_get_main_queue()];

2 扫描外设（discover），扫描外设的方法我们放在centralManager成功打开的委托中，因为只有设备成功打开，才能开始扫描，否则会报错。

????????-(void)centralManagerDidUpdateState:(CBCentralManager?*)central{ ????????????switch?(central.state)?{ ????????????????case?CBCentralManagerStateUnknown: ????????????????????NSLog(@">>>CBCentralManagerStateUnknown"); ????????????????????break; ????????????????case?CBCentralManagerStateResetting: ????????????????????NSLog(@">>>CBCentralManagerStateResetting"); ????????????????????break; ????????????????case?CBCentralManagerStateUnsupported: ????????????????????NSLog(@">>>CBCentralManagerStateUnsupported"); ????????????????????break; ????????????????case?CBCentralManagerStateUnauthorized: ????????????????????NSLog(@">>>CBCentralManagerStateUnauthorized"); ????????????????????break; ????????????????case?CBCentralManagerStatePoweredOff: ????????????????????NSLog(@">>>CBCentralManagerStatePoweredOff"); ????????????????????break; ????????????????case?CBCentralManagerStatePoweredOn: ????????????????????NSLog(@">>>CBCentralManagerStatePoweredOn"); ????????????????????//开始扫描周围的外设 ????????????????????/* ?????????????????????第一个参数nil就是扫描周围所有的外设，扫描到外设后会进入 ??????????????????????????-?(void)centralManager:(CBCentralManager?*)central?didDiscoverPeripheral:(CBPeripheral?*)peripheral?advertisementData:(NSDictionary?*)advertisementData?RSSI:(NSNumber?*)RSSI; ?????????????????????*/ ????????????????????[manager?scanForPeripheralsWithServices:nil?options:nil]; ????????????????????break; ????????????????default: ????????????????????break; ????????????} ????????} ????????//扫描到设备会进入方法 ????????-(void)centralManager:(CBCentralManager?*)central?didDiscoverPeripheral:(CBPeripheral?*)peripheral?advertisementData:(NSDictionary?*)advertisementData?RSSI:(NSNumber?*)RSSI{ ????????????NSLog(@"当扫描到设备:%@",peripheral.name); ????????????//接下来可以连接设备 ????????}

3 连接外设(connect)

????????//扫描到设备会进入方法 ????????-(void)centralManager:(CBCentralManager?*)central?didDiscoverPeripheral:(CBPeripheral?*)peripheral?advertisementData:(NSDictionary?*)advertisementData?RSSI:(NSNumber?*)RSSI{ ????????????//接下连接我们的测试设备，如果你没有设备，可以下载一个app叫lightbule的app去模拟一个设备 ????????????//这里自己去设置下连接规则，我设置的是P开头的设备 ???????????????????if?([peripheral.name?hasPrefix:@"P"]){ ???????????????????/* ???????????????????????一个主设备最多能连7个外设，每个外设最多只能给一个主设备连接,连接成功，失败，断开会进入各自的委托 ????????????????????-?(void)centralManager:(CBCentralManager?*)central?didConnectPeripheral:(CBPeripheral?*)peripheral; //连接外设成功的委托 ????????????????????-?(void)centralManager:(CBCentralManager?*)central?didFailToConnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error; //外设连接失败的委托 ????????????????????-?(void)centralManager:(CBCentralManager?*)central?didDisconnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error; //断开外设的委托 ????????????????????*/ ????????????????????//连接设备 ???????????????????[manager?connectPeripheral:peripheral?options:nil]; ???????????????} ????????} ????????//连接到Peripherals-成功 ????????-?(void)centralManager:(CBCentralManager?*)central?didConnectPeripheral:(CBPeripheral?*)peripheral ????????{ ????????????NSLog(@">>>连接到名称为（%@）的设备-成功",peripheral.name); ????????} ????????//连接到Peripherals-失败 ????????-(void)centralManager:(CBCentralManager?*)central?didFailToConnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error ????????{ ????????????NSLog(@">>>连接到名称为（%@）的设备-失败,原因:%@",[peripheral?name],[error?localizedDescription]); ????????} ????????//Peripherals断开连接 ????????-?(void)centralManager:(CBCentralManager?*)central?didDisconnectPeripheral:(CBPeripheral?*)peripheral?error:(NSError?*)error{ ????????????NSLog(@">>>外设连接断开连接?%@:?%@\n",?[peripheral?name],?[error?localizedDescription]); ????????}

4 扫描外设中的服务和特征(discover)
设备连接成功后，就可以扫描设备的服务了，同样是通过委托形式，扫描到结果后会进入委托方法。但是这个委托已经不再是主设备的委托（CBCentralManagerDelegate），而是外设的委托（CBPeripheralDelegate）,这个委托包含了主设备与外设交互的许多 回叫方法，包括获取services，获取characteristics，获取characteristics的值，获取characteristics的Descriptor，和Descriptor的值，写数据，读rssi，用通知的方式订阅数据等等。
4.1 获取外设的services

????????//连接到Peripherals-成功 ????????-?(void)centralManager:(CBCentralManager?*)central?didConnectPeripheral:(CBPeripheral?*)peripheral ????????{ ????????????NSLog(@">>>连接到名称为（%@）的设备-成功",peripheral.name); ????????????//设置的peripheral委托CBPeripheralDelegate ????????????//@interface?ViewController?:?UIViewController ????????????[peripheral?setDelegate:self]; ????????????//扫描外设Services，成功后会进入方法：-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverServices:(NSError?*)error{ ????????????[peripheral?discoverServices:nil]; ????????} ????????//扫描到Services ????????-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverServices:(NSError?*)error{ ????????????//??NSLog(@">>>扫描到服务：%@",peripheral.services); ????????????if?(error) ????????????{ ????????????????NSLog(@">>>Discovered?services?for?%@?with?error:?%@",?peripheral.name,?[error?localizedDescription]); ????????????????return; ????????????} ????????????for?(CBService?*service?in?peripheral.services)?{ ?????????????????????????????NSLog(@"%@",service.UUID); ?????????????????????????????//扫描每个service的Characteristics，扫描到后会进入方法：?-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverCharacteristicsForService:(CBService?*)service?error:(NSError?*)error ?????????????????????????????[peripheral?discoverCharacteristics:nil?forService:service]; ?????????????????????????} ????????}

4.2 获取外设的Characteristics,获取Characteristics的值，获取Characteristics的Descriptor和Descriptor的值

?????//扫描到Characteristics ?????-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverCharacteristicsForService:(CBService?*)service?error:(NSError?*)error{ ?????????if?(error) ?????????{ ?????????????NSLog(@"error?Discovered?characteristics?for?%@?with?error:?%@",?service.UUID,?[error?localizedDescription]); ?????????????return; ?????????} ?????????for?(CBCharacteristic?*characteristic?in?service.characteristics) ?????????{ ?????????????NSLog(@"service:%@?的?Characteristic:?%@",service.UUID,characteristic.UUID); ?????????} ?????????//获取Characteristic的值，读到数据会进入方法：-(void)peripheral:(CBPeripheral?*)peripheral?didUpdateValueForCharacteristic:(CBCharacteristic?*)characteristic?error:(NSError?*)error ?????????for?(CBCharacteristic?*characteristic?in?service.characteristics){ ?????????????{ ?????????????????[peripheral?readValueForCharacteristic:characteristic]; ?????????????} ?????????} ?????????//搜索Characteristic的Descriptors，读到数据会进入方法：-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverDescriptorsForCharacteristic:(CBCharacteristic?*)characteristic?error:(NSError?*)error ?????????for?(CBCharacteristic?*characteristic?in?service.characteristics){ ?????????????[peripheral?discoverDescriptorsForCharacteristic:characteristic]; ?????????} ?????} ????//获取的charateristic的值 ????-(void)peripheral:(CBPeripheral?*)peripheral?didUpdateValueForCharacteristic:(CBCharacteristic?*)characteristic?error:(NSError?*)error{ ????????//打印出characteristic的UUID和值 ????????//!注意，value的类型是NSData，具体开发时，会根据外设协议制定的方式去解析数据 ????????NSLog(@"characteristic?uuid:%@??value:%@",characteristic.UUID,characteristic.value); ????} ????//搜索到Characteristic的Descriptors ????-(void)peripheral:(CBPeripheral?*)peripheral?didDiscoverDescriptorsForCharacteristic:(CBCharacteristic?*)characteristic?error:(NSError?*)error{ ????????//打印出Characteristic和他的Descriptors ?????????NSLog(@"characteristic?uuid:%@",characteristic.UUID); ????????for?(CBDescriptor?*d?in?characteristic.descriptors)?{ ????????????NSLog(@"Descriptor?uuid:%@",d.UUID); ????????} ????} ????//获取到Descriptors的值 ????-(void)peripheral:(CBPeripheral?*)peripheral?didUpdateValueForDescriptor:(CBDescriptor?*)descriptor?error:(NSError?*)error{ ????????//打印出DescriptorsUUID?和value ????????//这个descriptor都是对于characteristic的描述，一般都是字符串，所以这里我们转换成字符串去解析 ????????NSLog(@"characteristic?uuid:%@??value:%@",[NSString?stringWithFormat:@"%@",descriptor.UUID],descriptor.value); ????}

5 把数据写到Characteristic中

????//写数据 ????-(void)writeCharacteristic:(CBPeripheral?*)peripheral ????????????????characteristic:(CBCharacteristic?*)characteristic ?????????????????????????value:(NSData?*)value{ ????????//打印出?characteristic?的权限，可以看到有很多种，这是一个NS_OPTIONS，就是可以同时用于好几个值，常见的有read，write，notify，indicate，知知道这几个基本就够用了，前连个是读写权限，后两个都是通知，两种不同的通知方式。 ????????/* ?????????typedef?NS_OPTIONS(NSUInteger,?CBCharacteristicProperties)?{ ?????????CBCharacteristicPropertyBroadcast??????????????????????????????????????????????=?0x01, ?????????CBCharacteristicPropertyRead???????????????????????????????????????????????????=?0x02, ?????????CBCharacteristicPropertyWriteWithoutResponse???????????????????????????????????=?0x04, ?????????CBCharacteristicPropertyWrite??????????????????????????????????????????????????=?0x08, ?????????CBCharacteristicPropertyNotify?????????????????????????????????????????????????=?0x10, ?????????CBCharacteristicPropertyIndicate???????????????????????????????????????????????=?0x20, ?????????CBCharacteristicPropertyAuthenticatedSignedWrites??????????????????????????????=?0x40, ?????????CBCharacteristicPropertyExtendedProperties?????????????????????????????????????=?0x80, ?????????CBCharacteristicPropertyNotifyEncryptionRequired?NS_ENUM_AVAILABLE(NA,?6_0)????????=?0x100, ?????????CBCharacteristicPropertyIndicateEncryptionRequired?NS_ENUM_AVAILABLE(NA,?6_0)??=?0x200 ?????????}; ?????????*/ ????????NSLog(@"%lu",?(unsigned?long)characteristic.properties); ????????//只有?characteristic.properties?有write的权限才可以写 ????????if(characteristic.properties?&?CBCharacteristicPropertyWrite){ ????????????/* ????????????????最好一个type参数可以为CBCharacteristicWriteWithResponse或type:CBCharacteristicWriteWithResponse,区别是是否会有反馈 ????????????*/ ????????????[peripheral?writeValue:value?forCharacteristic:characteristic?type:CBCharacteristicWriteWithResponse]; ????????}else{ ????????????NSLog(@"该字段不可写！"); ????????} ????}

6 订阅Characteristic的通知

????//设置通知 ????-(void)notifyCharacteristic:(CBPeripheral?*)peripheral ????????????????characteristic:(CBCharacteristic?*)characteristic{ ????????//设置通知，数据通知会进入：didUpdateValueForCharacteristic方法 ????????[peripheral?setNotifyValue:YES?forCharacteristic:characteristic]; ????} ????//取消通知 ????-(void)cancelNotifyCharacteristic:(CBPeripheral?*)peripheral ?????????????????characteristic:(CBCharacteristic?*)characteristic{ ?????????[peripheral?setNotifyValue:NO?forCharacteristic:characteristic]; ????}

7 断开连接(disconnect)

????//停止扫描并断开连接 ????-(void)disconnectPeripheral:(CBCentralManager?*)centralManager ?????????????????????peripheral:(CBPeripheral?*)peripheral{ ????????//停止扫描 ????????[centralManager?stopScan]; ????????//断开连接 ????????[centralManager?cancelPeripheralConnection:peripheral]; ????}

8 模拟器蓝牙调试，慎用，最好还是用真机去调试。
由于在iPhone 4s之后的iOS才支持BLE，新一代的这些iOS设备又都不便宜，在做测试的时候，用iOS模拟器进行调试，可以节约一些开发成本。怎么在iOS模拟器上调试BLE，
苹果最初给出的说明是，支持BLE的mac机子上可以用模拟器进行调试，并给出了一份技术文档（传送门），恶心的是，后来苹果抽风，又把这份文档移除，
并且把iOS 7.0的模拟器上对BLE的支持也移除掉了（难道是想让大家多买设备测试？Apple sucks.）后面，网上搜了一下，解决办法如下：
1. 买一个CSR蓝牙4.0 USB适配器（某宝上大概30块钱），在机子上插入该物（你懂的）
2. 在Terminal下敲入sudo nvram bluetoothHostControllerSwitchBehavior="never" ， 重启Mac。
3. 用XCode 4.6调试代码，在iOS 6.1的模拟器上跑程序（用XCode 5.0跑iOS 7.0模拟器会抛异常，原因上面详诉过了，Apple sucks，你懂的）
如何降低模拟器的iOS版本呢？
XCode->Preferences->Downloads里面有很多simulators你可以下载
选择个6.1的下载好了
代码下载:
我博客中大部分示例代码都上传到了github，地址是：https://github.com/coolnameismy/demo
本文代码存放目录是BleDemo

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