若想在裝置上實現Central角色的功能，主要有以下步驟：

2.搜尋周圍廣播的裝置

3.與一個外設進行連線，並探索外設提供的服務

4.向外設傳送讀寫characteristic的請求，如果有需要訂閱characteristic值得更新，來跟蹤資料的變化。

myCentralManager =
        [[CBCentralManager alloc] initWithDelegate:self queue:nil options:nil];

[myCentralManager scanForPeripheralsWithServices:nil options:nil];

//CBCentralManager代理方法
- (void)centralManager:(CBCentralManager *)central
 didDiscoverPeripheral:(CBPeripheral *)peripheral
     advertisementData:(NSDictionary *)advertisementData
                  RSSI:(NSNumber *)RSSI {
 
    NSLog(@"Discovered %@", peripheral.name);
    self.discoveredPeripheral = peripheral;
    ...
}
 

選擇需要的外設並建立連線，並設定外設的代理為self，用於與外設的互動

[myCentralManager connectPeripheral:peripheral options:nil];

- (void)centralManager:(CBCentralManager *)central
  didConnectPeripheral:(CBPeripheral *)peripheral {
 
    NSLog(@"Peripheral connected");
    peripheral.delegate = self;//
    ...
}

搜尋外設提供的服務並讀取資料

[peripheral discoverServices:nil];

- (void)peripheral:(CBPeripheral *)peripheral
didDiscoverServices:(NSError *)error {
 
    for (CBService *service in peripheral.services) {
        NSLog(@"Discovered service %@", service);
        ...
    }
    ...
}
 

停止搜尋外設

[myCentralManager stopScan];

從服務中獲取特徵

NSLog(@"Discovering characteristics for service %@", interestingService);
    [peripheral discoverCharacteristics:nil forService:interestingService];

- (void)peripheral:(CBPeripheral *)peripheral
didDiscoverCharacteristicsForService:(CBService *)service
             error:(NSError *)error {
 
    for (CBCharacteristic *characteristic in service.characteristics) {
        NSLog(@"Discovered characteristic %@", characteristic);
        ...
    }
    ...
}
 

從特徵中讀取資料

NSLog(@"Reading value for characteristic %@", interestingCharacteristic);
    [peripheral readValueForCharacteristic:interestingCharacteristic];

- (void)peripheral:(CBPeripheral *)peripheral
didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic
             error:(NSError *)error {
 
    NSData *data = characteristic.value;
    // parse the data as needed
    ...
}

如果需要獲取動態變化的特徵，需要訂閱特徵變化的通知

[peripheral setNotifyValue:YES forCharacteristic:interestingCharacteristic];

- (void)peripheral:(CBPeripheral *)peripheral
didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic
             error:(NSError *)error {
 
    if (error) {
        NSLog(@"Error changing notification state: %@",
           [error localizedDescription]);
    }
    ...
}

向外設寫資料

NSLog(@"Writing value for characteristic %@", interestingCharacteristic);
    [peripheral writeValue:dataToWrite forCharacteristic:interestingCharacteristic
        type:CBCharacteristicWriteWithResponse];

- (void)peripheral:(CBPeripheral *)peripheral
didWriteValueForCharacteristic:(CBCharacteristic *)characteristic
             error:(NSError *)error {
 
    if (error) {
        NSLog(@"Error writing characteristic value: %@",
            [error localizedDescription]);
    }
    ...
}

需要注意一下事項：

由於藍芽是共享無線電硬體裝置的來發送和接受資料的，可能其他無線通訊也需要使用無線電硬體，例如Wifi,或者其他App也正在使用藍芽，因此，應該儘量避免長時間使用無線電。可以通過以下方式來對其進行優化

1.只在需要時進行藍芽外設搜尋，當建立與外設的連線後，應停止搜尋。呼叫stopScan方法

3.準確的獲取外設的資料，而不是搜尋外設提供的所有的資料，[peripheral discoverServices:@[firstServiceUUID, secondServiceUUID]];

4.當不再獲取資料時，取消對資料的訂閱，斷開與外設的連線

[myCentralManager cancelPeripheralConnection:peripheral];

重連外設

Figure 5-1  A sample reconnection workflow