本文從以下三方面講解下藍牙開發
1、藍牙相關基本知識
2、藍牙相關類圖
3、藍牙交互流程
一、藍牙相關基本知識
涉及到藍牙開發，首先有幾個問題是需要我們理解的
1、任何設備既可以是中心設備、也可以是外圍設備
2、外設 和 中心設備 之間通過特征建立一個雙向的數據通道
3、CBCentralManager主要操作中心設備，處理鏈接上外設之前的操作，鏈接上外設后，主要靠CBPeripheral（主要操作外設）處理外設相關操作（服務、特征、數據讀寫）
4、中心設備管理 CBCentralManager
中心控制類，主要管理中心設備，以及處理跟外設（外圍設備）相關操作，主要是掃描、鏈接、斷開外設。
操作中心設備的核心類。
很重要的協議CBCentralManagerDelegate，包含中心設備狀態（是否打開藍牙）回調、發現外設回調、鏈接外設成功回調、鏈接外設失敗回調、外設鏈接斷開回調等方法。
一個中心設備可以鏈接多個外圍設備。
5、外圍設備 CBPeripheral
外設類，包含設備的基礎屬性，名字，uuid等信息。向外設寫入數據。
當中心設備連接到外設后，需要通過外設對象的代理方法進行數據交互。
操作外圍設備的核心類。
很重要的協議CBPeripheralDelegate，包含發現服務回調、發現特征回調、特征的通知設置改變回調、特征更新回調、特征已寫入數據回調等方法。
一個設備包含多個服務、一個服務包含多個特征、一個特征又包含多個描述。
6、外圍設備管理 CBPeripheralManager
設備的控制，主要可以為設備設置Service以及Characteristic，可以手動配置特定的服務和特征值，也可看作可以自定義藍牙協議，例如將手機作為外設時可以為自己的手機藍牙設置服務和特征值。CBCentralManager更適合將自己的軟件作為中心。
用的較少
7、服務 CBService
服務對象是用來管理外設提供的一些數據服務的。
一個服務可以包含多個特征
8、特征 CBCharacteristic
通過綁定服務中的特征值來進行數據的讀寫操作。
特征就是具體鍵值對，提供數據的地方。
每個特征屬性分為這么幾種：讀，寫，通知等幾種方式。
有時讀、寫、通知可以是同一個特征，也可以讀、寫、通知各用一個特征表示。
一個特征可以包含多個描述。
一般我們操作到特征這一層
9、描述 CBDescriptor
每個characteristic可以對應一個或多個Description 供用戶描述characteristic的信息或屬性。
10、CBAttribute
CBService，CBCharacteristic，CBDescriptor 類都繼承自 CBAttribute，
它們有一個共同的屬性 CBUUID，用來作為唯一的標識。
二、藍牙相關類圖
下面用類圖簡述下：
一個中心設備可以連接多個外設，一個外設包含多個服務，一個服務包含多個特征，一個特征包含多個描述
服務、特征、描述都用CBUUID唯一標識
三、藍牙交互流程
下面簡述下以手機作為中心設備、其它作為外圍設備的交互流程，大致流程如圖所示
下面是操作詳解
1、創建中心設備管理對象（初始化中心設備）
CBCentralManager 的創建是異步的，如果初始化完成之后沒有被當前創建它的類所持有，就會在下一次 RunLoop 迭代的時候釋放。
創建線程寫nil，為主線程。
初始化成功后，就會觸發 CBCentralManagerDelegate 中的中心設備狀態更新方法：centralManagerDidUpdateState:
NSDictionary *options = @{CBCentralManagerOptionShowPowerAlertKey:@NO};
self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil options:options];
/*! * @method initWithDelegate:queue:options: * * @param delegate The delegate that will receive central role events. * @param queue The dispatch queue on which the events will be dispatched. * @param options An optional dictionary specifying options for the manager. * * @discussion The initialization call. The events of the central role will be dispatched on the provided queue. * If <i>nil</i>, the main queue will be used. * * @seealso CBCentralManagerOptionShowPowerAlertKey * @seealso CBCentralManagerOptionRestoreIdentifierKey * */ - (instancetype)initWithDelegate:(nullable id<CBCentralManagerDelegate>)delegate queue:(nullable dispatch_queue_t)queue options:(nullable NSDictionary<NSString *, id> *)options NS_AVAILABLE(10_9, 7_0) NS_DESIGNATED_INITIALIZER;
@protocol CBCentralManagerDelegate <NSObject> @required /*! * @method centralManagerDidUpdateState: * * @param central The central manager whose state has changed. * * @discussion Invoked whenever the central manager's state has been updated. Commands should only be issued when the state is * <code>CBCentralManagerStatePoweredOn</code>. A state below <code>CBCentralManagerStatePoweredOn</code> * implies that scanning has stopped and any connected peripherals have been disconnected. If the state moves below * <code>CBCentralManagerStatePoweredOff</code>, all <code>CBPeripheral</code> objects obtained from this central * manager become invalid and must be retrieved or discovered again. * * @see state * */ - (void)centralManagerDidUpdateState:(CBCentralManager *)central;
2、掃描外圍設備
在CBCentralManagerDelegate 中的中心設備狀態更新方法：centralManagerDidUpdateState:中，
當中心設備處於CBManagerStatePoweredOn 狀態的時候開始掃描周邊設備（可以使用指定的 UUID 發現特定的 Service，也可以傳入 nil，表示發現所有周邊的藍牙設備，不過還是建議只發現自己需要服務的設備）。
掃描外設：scanForPeripheralsWithServices:options:
該操作由CBCentralManager對象通過scanForPeripheralsWithServices:options:方法實現
case CBManagerStatePoweredOn: //藍牙正常開啟 [self startScan]; break;
- (void)startScan { // [self.centralManager scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey : @YES }]; // 掃描所有設備 當指定設備不好使時可以使用該方法 // [self.centralManager scanForPeripheralsWithServices:nil options:nil]; // 掃描指定設備 快速 [self.centralManager scanForPeripheralsWithServices:@[[CBUUID UUIDWithString:self.peripheralServiceUUID]] options:nil]; [self startTime]; }
/*! * @method scanForPeripheralsWithServices:options: * * @param serviceUUIDs A list of <code>CBUUID</code> objects representing the service(s) to scan for. * @param options An optional dictionary specifying options for the scan. * * @discussion Starts scanning for peripherals that are advertising any of the services listed in <i>serviceUUIDs</i>. Although strongly discouraged, * if <i>serviceUUIDs</i> is <i>nil</i> all discovered peripherals will be returned. If the central is already scanning with different * <i>serviceUUIDs</i> or <i>options</i>, the provided parameters will replace them. * Applications that have specified the <code>bluetooth-central</code> background mode are allowed to scan while backgrounded, with two * caveats: the scan must specify one or more service types in <i>serviceUUIDs</i>, and the <code>CBCentralManagerScanOptionAllowDuplicatesKey</code> * scan option will be ignored. * * @see centralManager:didDiscoverPeripheral:advertisementData:RSSI: * @seealso CBCentralManagerScanOptionAllowDuplicatesKey * @seealso CBCentralManagerScanOptionSolicitedServiceUUIDsKey * */ - (void)scanForPeripheralsWithServices:(nullable NSArray<CBUUID *> *)serviceUUIDs options:(nullable NSDictionary<NSString *, id> *)options;
3、發現外圍設備
CBCentralManager對象執行掃描外設方法scanForPeripheralsWithServices:options:后
會觸發 CBCentralManagerDelegate 中的方法：（發現外設）centralManager:didDiscoverPeripheral:advertisementData:RSSI:
如果在掃描時指定了明確的服務，那么此時該方法里的外設就是包含該服務的外設，
如果傳入的是nil，那么此時該方法里的外設就是周邊所有打開的藍牙設備。
/*! * @method centralManager:didDiscoverPeripheral:advertisementData:RSSI: * * @param central The central manager providing this update. * @param peripheral A <code>CBPeripheral</code> object. * @param advertisementData A dictionary containing any advertisement and scan response data. * @param RSSI The current RSSI of <i>peripheral</i>, in dBm. A value of <code>127</code> is reserved and indicates the RSSI * was not available. * * @discussion This method is invoked while scanning, upon the discovery of <i>peripheral</i> by <i>central</i>. A discovered peripheral must * be retained in order to use it; otherwise, it is assumed to not be of interest and will be cleaned up by the central manager. For * a list of <i>advertisementData</i> keys, see {@link CBAdvertisementDataLocalNameKey} and other similar constants. * * @seealso CBAdvertisementData.h * */ - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *, id> *)advertisementData RSSI:(NSNumber *)RSSI;
4、鏈接外設
在CBCentralManagerDelegate 中的發現外設方法：centralManager:didDiscoverPeripheral:advertisementData:RSSI:中，
我們會鏈接外設：connectPeripheral:options:
該操作由CBCentralManager對象通過connectPeripheral:options:方法實現
我們通過名稱或者廠商數據來確定我們需要鏈接的外設（過濾外設），找到后停止掃描，然后鏈接該外設，即鏈接指定外設
[central connectPeripheral:peripheral options:nil];
/*! * @method connectPeripheral:options: * * @param peripheral The <code>CBPeripheral</code> to be connected. * @param options An optional dictionary specifying connection behavior options. * * @discussion Initiates a connection to <i>peripheral</i>. Connection attempts never time out and, depending on the outcome, will result * in a call to either {@link centralManager:didConnectPeripheral:} or {@link centralManager:didFailToConnectPeripheral:error:}. * Pending attempts are cancelled automatically upon deallocation of <i>peripheral</i>, and explicitly via {@link cancelPeripheralConnection}. * * @see centralManager:didConnectPeripheral: * @see centralManager:didFailToConnectPeripheral:error: * @seealso CBConnectPeripheralOptionNotifyOnConnectionKey * @seealso CBConnectPeripheralOptionNotifyOnDisconnectionKey * @seealso CBConnectPeripheralOptionNotifyOnNotificationKey * @seealso CBConnectPeripheralOptionEnableTransportBridgingKey * @seealso CBConnectPeripheralOptionRequiresANCS * */ - (void)connectPeripheral:(CBPeripheral *)peripheral options:(nullable NSDictionary<NSString *, id> *)options;
5、鏈接外設結果回調
CBCentralManager對象執行鏈接外設方法connectPeripheral:options:后
會觸發 CBCentralManagerDelegate 中的方法：
鏈接外設成功回調：centralManager:didConnectPeripheral:
/*! * @method centralManager:didConnectPeripheral: * * @param central The central manager providing this information. * @param peripheral The <code>CBPeripheral</code> that has connected. * * @discussion This method is invoked when a connection initiated by {@link connectPeripheral:options:} has succeeded. * */ - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;
鏈接外設失敗回調：centralManager:didFailToConnectPeripheral:error:
/*! * @method centralManager:didFailToConnectPeripheral:error: * * @param central The central manager providing this information. * @param peripheral The <code>CBPeripheral</code> that has failed to connect. * @param error The cause of the failure. * * @discussion This method is invoked when a connection initiated by {@link connectPeripheral:options:} has failed to complete. As connection attempts do not * timeout, the failure of a connection is atypical and usually indicative of a transient issue. * */ - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(nullable NSError *)error;
6、查找服務
在CBCentralManagerDelegate 中的鏈接外設成功回調方法：centralManager:didConnectPeripheral:中，
我們會查找服務：discoverServices:
該操作由CBPeripheral對象通過discoverServices:方法實現
[peripheral discoverServices:@[[CBUUID UUIDWithString:self.peripheralServiceUUID]]];
/*! * @method discoverServices: * * @param serviceUUIDs A list of <code>CBUUID</code> objects representing the service types to be discovered. If <i>nil</i>, * all services will be discovered. * * @discussion Discovers available service(s) on the peripheral. * * @see peripheral:didDiscoverServices: */ - (void)discoverServices:(nullable NSArray<CBUUID *> *)serviceUUIDs;
7、發現服務
CBPeripheral對象執行查找服務方法discoverServices:后，
會觸發 CBPeripheralDelegate 中的發現服務方法：peripheral:didDiscoverServices:
/*! * @method peripheral:didDiscoverServices: * * @param peripheral The peripheral providing this information. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link discoverServices: @/link call. If the service(s) were read successfully, they can be retrieved via * <i>peripheral</i>'s @link services @/link property. * */ - (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(nullable NSError *)error;
8、查找特征
在 CBPeripheralDelegate 中的發現服務方法：peripheral:didDiscoverServices:中，
我們會查找特征：discoverCharacteristics:forService:
該操作由CBPeripheral對象通過discoverCharacteristics:forService:方法實現
[peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:self.peripheralCharacteristicRTXUUID]] forService:service];
/*! * @method discoverCharacteristics:forService: * * @param characteristicUUIDs A list of <code>CBUUID</code> objects representing the characteristic types to be discovered. If <i>nil</i>, * all characteristics of <i>service</i> will be discovered. * @param service A GATT service. * * @discussion Discovers the specified characteristic(s) of <i>service</i>. * * @see peripheral:didDiscoverCharacteristicsForService:error: */ - (void)discoverCharacteristics:(nullable NSArray<CBUUID *> *)characteristicUUIDs forService:(CBService *)service;
9、發現特征
CBPeripheral對象執行查找特征方法discoverCharacteristics:forService:后，
會觸發CBPeripheralDelegate 中的發現特征方法：peripheral:didDiscoverCharacteristicsForService:error:
/*! * @method peripheral:didDiscoverCharacteristicsForService:error: * * @param peripheral The peripheral providing this information. * @param service The <code>CBService</code> object containing the characteristic(s). * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link discoverCharacteristics:forService: @/link call. If the characteristic(s) were read successfully, * they can be retrieved via <i>service</i>'s <code>characteristics</code> property. */ - (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(nullable NSError *)error;
10、寫特征、通知特征（讀取）、讀特征
在 CBPeripheralDelegate 中的發現特征方法：peripheral:didDiscoverCharacteristicsForService:error:中，
我們會處理特征（讀、寫、通知），一般會保存寫入特征，方便后期寫入數據，打開使能通知，方便讀取數據
寫：
保存寫特征，方便后期寫入數據。
讀：
通知特征和讀特征都是為了讀取，一般我們使用的都是通知，
使用通知的時候，要打開使能通知（訂閱），
該操作由CBPeripheral對象通過setNotifyValue:forCharacteristic:方法打開指定通知特征
通知特征發送的數據在didUpdateValueForCharacteristic方法里接受（讀取）
該操作會回調CBPeripheralDelegate 中的方法peripheral:didUpdateNotificationStateForCharacteristic:error:
通過characteristic.isNotifying知曉通知狀態
/*! * @method peripheral:didUpdateNotificationStateForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link setNotifyValue:forCharacteristic: @/link call. */ - (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
for (CBCharacteristic *characteristic in service.characteristics) { // if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:self.peripheralCharacteristicTXUUID]]) { // // 打開使能通知 （訂閱）該特征發送的數據在didUpdateValueForCharacteristic方法里接受（讀取） // [peripheral setNotifyValue:YES forCharacteristic:characteristic]; // } else if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:self.peripheralCharacteristicRXUUID]]) { // // 保存外設接受特征（寫入特征） // self.characteristicRX = characteristic;
11、寫入數據
寫入方法：writeValue:forCharacteristic:type:
寫入操作由CBPeripheral對象通過writeValue:forCharacteristic:type:方法寫入指定寫入特征
[self.peripheral writeValue:peripheralRXData forCharacteristic:self.characteristicRX type:
CBCharacteristicWriteWithResponse];
/*! * @method writeValue:forCharacteristic:type: * * @param data The value to write. * @param characteristic The characteristic whose characteristic value will be written. * @param type The type of write to be executed. * * @discussion Writes <i>value</i> to <i>characteristic</i>'s characteristic value. * If the <code>CBCharacteristicWriteWithResponse</code> type is specified, {@link peripheral:didWriteValueForCharacteristic:error:} * is called with the result of the write request. * If the <code>CBCharacteristicWriteWithoutResponse</code> type is specified, and canSendWriteWithoutResponse is false, the delivery * of the data is best-effort and may not be guaranteed. * * @see peripheral:didWriteValueForCharacteristic:error: * @see peripheralIsReadyToSendWriteWithoutResponse: * @see canSendWriteWithoutResponse * @see CBCharacteristicWriteType */ - (void)writeValue:(NSData *)data forCharacteristic:(CBCharacteristic *)characteristic type:(CBCharacteristicWriteType)type;
寫入數據有兩種方式：
/* 32 typedef NS_ENUM(NSInteger, CBCharacteristicWriteType) { 33 CBCharacteristicWriteWithResponse = 0,//寫數據並且接收成功與否回執 34 CBCharacteristicWriteWithoutResponse,//寫數據不接收回執 35 }; 36 */
如果寫入類型為CBCharacteristicWriteWithResponse 回調CBPeripheralDelegate 中的方法：
peripheral:didWriteValueForCharacteristic:error:，
如果寫入類型為CBCharacteristicWriteWithoutResponse不回調此方法，
該方法只是告知寫入數據是否成功
/*! * @method peripheral:didWriteValueForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a {@link writeValue:forCharacteristic:type:} call, when the <code>CBCharacteristicWriteWithResponse</code> type is used. */ - (void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
寫入數據后外設響應數據在特征值更新方法didUpdateValueForCharacteristic:error:中讀取
12、讀取數據
讀取外設發送給中心設備的數據，
無論是read的回調，還是notify（訂閱）的回調都是CBPeripheralDelegate 中的方法：
特征值更新：didUpdateValueForCharacteristic:error:
/*! * @method peripheral:didUpdateValueForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method is invoked after a @link readValueForCharacteristic: @/link call, or upon receipt of a notification/indication. */ - (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
13、斷開鏈接
斷開鏈接：cancelPeripheralConnection:
斷開鏈接操作由CBCentralManager對象通過cancelPeripheralConnection:方法實現
該方法不會觸發CBCentralManagerDelegate 中的方法：
斷開外設（僅在異常斷開時會觸發）：centralManager:didDisconnectPeripheral:error:
/*! * @method cancelPeripheralConnection: * * @param peripheral A <code>CBPeripheral</code>. * * @discussion Cancels an active or pending connection to <i>peripheral</i>. Note that this is non-blocking, and any <code>CBPeripheral</code> * commands that are still pending to <i>peripheral</i> may or may not complete. * * @see centralManager:didDisconnectPeripheral:error: * */ - (void)cancelPeripheralConnection:(CBPeripheral *)peripheral;
參考資料：