首先引入库CoreBluetooth.framework
引入头文件
#import <CoreBluetooth/CoreBluetooth.h>

遵守代理
CBPeripheralDelegate,CBCentralManagerDelegate
#pragma mark - 蓝牙
@property BOOL cbReady;
@property (nonatomic, strong) CBCentralManager *manager;
@property (nonatomic, strong) CBPeripheral *peripheral;
@property (strong ,nonatomic) CBCharacteristic *writeCharacteristic;
@property (strong,nonatomic) NSMutableArray *nDevices;
@property (strong,nonatomic) NSMutableArray *nServices;
@property (strong,nonatomic) NSMutableArray *nCharacteristics;
@property (nonatomic,strong) NSMutableArray *nPeripherals;

#pragma mark - 蓝牙
- (void)initBluetooth
{
    //实例化
    _manager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];
    _cbReady = false;
    _nDevices = [[NSMutableArray alloc]init];
    _nServices = [[NSMutableArray alloc]init];
    _nCharacteristics = [[NSMutableArray alloc]init];
    _nPeripherals = [[NSMutableArray alloc] init];
}
//扫描
-(void)scanBluetooth
{
    NSLog(@"正在扫描外设...");
    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];
    [_manager scanForPeripheralsWithServices:nil options:options];
    
    double delayInSeconds = 10.0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        [self.manager stopScan];
        NSLog(@"扫描超时,停止扫描");
    });
}
//开始查看服务，蓝牙开启
-(void)centralManagerDidUpdateState:(CBCentralManager *)central
{
    switch (central.state) {
        case CBCentralManagerStatePoweredOn:
            NSLog(@"蓝牙已打开,请扫描外设");
            [self scanBluetooth];break;
        case CBCentralManagerStatePoweredOff:
            NSLog(@"请打开蓝牙");break;
        default:
            break;
    }
}

//查到外设后，停止扫描，连接设备
-(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
{
    [_nPeripherals addObject:peripheral];
    NSLog(@"%@",[NSString stringWithFormat:@"已发现 peripheral: %@ rssi: %@, name: %@ advertisementData: %@ ", peripheral, RSSI, peripheral.name, advertisementData]);

    
    BOOL replace = NO;
    // Match if we have this device from before
    for (int i=0; i < _nDevices.count; i++) {
        CBPeripheral *p = [_nDevices objectAtIndex:i];
        if ([p isEqual:peripheral]) {
            [_nDevices replaceObjectAtIndex:i withObject:peripheral];
            replace = YES;
        }
    }
    if (!replace) {
        [_nDevices addObject:peripheral];
    }
    for(int i = 0;i < _nPeripherals.count;i++)
    {
        CBPeripheral *per = [_nPeripherals objectAtIndex:i];
        NSLog(@"%@ - %@ - %d",per.name,[[NSUserDefaults standardUserDefaults] objectForKey:@"m_device"],[per.name isEqualToString:[[NSUserDefaults standardUserDefaults] objectForKey:@"m_device"]]);

        if([per.name isEqualToString:[[NSUserDefaults standardUserDefaults] objectForKey:@"m_device"]])
        {
            _peripheral = per;
            
                       //连接蓝牙
            [self.manager connectPeripheral:_peripheral options:nil];
            [self.manager stopScan];//停止扫描
            return;
        }
        else
        {
            //重新扫描
            [self scanBluetooth];
        }
    }
}
//连接外设成功，开始发现服务
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral {
    
    NSLog(@"%@",[NSString stringWithFormat:@"成功连接 peripheral: %@ with name:%@ identifier = %@ name:%@",peripheral,peripheral.name,peripheral.identifier,peripheral.name]);
    [self.peripheral setDelegate:self];
    [self.peripheral discoverServices:nil];
}
//连接外设失败
-(void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
{
    NSLog(@"连接外设失败 = %@",error);
}
//已发现服务
-(void) peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
    
    NSLog(@"发现服务.");
    
    int i=0;
    for (CBService *service in peripheral.services) {
        [self.nServices addObject:service];
    }
    for (CBService *service in peripheral.services) {
        
        NSLog(@"%@",[NSString stringWithFormat:@"%d :服务 UUID: %@(%@)",i,service.UUID.data,service.UUID]);
        i++;
        [peripheral discoverCharacteristics:nil forService:service];
    }
}

//已搜索到Characteristics
-(void) peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
    NSLog(@"%@",[NSString stringWithFormat:@"发现特征的服务:%@ (%@)",service.UUID.data ,service.UUID]);
    
    for (CBCharacteristic *characteristic in service.characteristics) {
        NSLog(@"%@",[NSString stringWithFormat:@"特征 UUID: %@",characteristic.UUID]);
        //FFE1服务 FFE2读 FFE3写
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"FFE3"]]) {
            _writeCharacteristic = characteristic;
            
            
            [_peripheral writeValue:[[NSString stringWithFormat:@"m1=200\n"] dataUsingEncoding:NSUTF8StringEncoding] forCharacteristic:_writeCharacteristic type:CBCharacteristicWriteWithResponse];
            ((UIButton *)[self.view viewWithTag:10]).selected = YES;
            
            
        }
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"FFE2"]]) {
            [_peripheral readValueForCharacteristic:characteristic];
            [self.peripheral setNotifyValue:YES forCharacteristic:characteristic];
        }
        [_nCharacteristics addObject:characteristic];
    }
}
//获取外设发来的数据，不论是read和notify,获取数据都是从这个方法中读取。
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"FFE2"]]) {
        NSLog(@"接收数据 = %@",[[NSString alloc] initWithData:characteristic.value encoding:NSUTF8StringEncoding]);
       
        _flagFinish = [[NSString alloc] initWithData:characteristic.value encoding:NSUTF8StringEncoding];
        NSLog(@"_flagFinish = %@",_flagFinish);
        
    }
}

//中心读取外设实时数据
- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error {
    if (error) {
        NSLog(@"中心读取外设实时数据失败 %@", error.localizedDescription);
    }
    // Notification has started
    if (characteristic.isNotifying == YES) {
        [peripheral readValueForCharacteristic:characteristic];
        //        [self.peripheral setNotifyValue:YES forCharacteristic:characteristic];
        
        
    } else { // Notification has stopped
        // so disconnect from the peripheral
        NSLog(@"Notification stopped on %@.  Disconnecting", characteristic);
        [self.manager cancelPeripheralConnection:self.peripheral];
    }
    NSLog(@"接收数据 = %@",[[NSString alloc] initWithData:characteristic.value encoding:NSUTF8StringEncoding]);
}
//用于检测中心向外设写数据是否成功
-(void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    if (error) {
        NSLog(@"发送数据失败=======%@",error.userInfo);
    }else{
        NSLog(@"发送数据成功");
    }
}

注释：每一个蓝牙对应的特征服务都是不一样的，具体要看蓝牙的说明文档。