博客

有时我们需要将我们的设备作为外设，来为其他中心设备提供服务。需要以下步骤：

1.创建一个CBPeripheralManager实例

2.基于peripheral实例，创建services和characteristics实例。

3.发布services和characteristics到你设备本地数据库

4.广播你创建的服务

5.对中心设备的读写请求做出相应，向订阅数据的中心设备发送数据更新通知

 myPeripheralManager =
        [[CBPeripheralManager alloc] initWithDelegate:self queue:nil options:nil];

通过唯一的UUID来标示你创建的characteristics和services,UUID为128位，可以通过命令行uuidgen来产生多个UUID，一些通用的UUID为16位标示，但是系统会默认将其补充为128位。自己生成的UUID必须为128位。

CBUUID *heartRateServiceUUID = [CBUUID UUIDWithString: @"180D"];//180D为通用的心率服务ID

 CBUUID *myCustomServiceUUID =
        [CBUUID UUIDWithString:@"71DA3FD1-7E10-41C1-B16F-4430B506CDE7"];

myCharacteristic =
        [[CBMutableCharacteristic alloc] initWithType:myCharacteristicUUID
         properties:CBCharacteristicPropertyRead
         value:myValue permissions:CBAttributePermissionsReadable];//创建特征

myService = [[CBMutableService alloc] initWithType:myServiceUUID primary:YES];//创建服务

myService.characteristics = @[myCharacteristic];//

[myPeripheralManager addService:myService];//发布服务,发布之后会加入到本地数据库，之后就不能修改服务了

// CBPeripheralManagerDelegate
- (void)peripheralManager:(CBPeripheralManager *)peripheral
            didAddService:(CBService *)service
                    error:(NSError *)error {
 
    if (error) {
        NSLog(@"Error publishing service: %@", [error localizedDescription]);
    }
    ...
}

发布服务到本地数据库之后就可以广播服务了

[myPeripheralManager startAdvertising:@{ CBAdvertisementDataServiceUUIDsKey :
        @[myFirstService.UUID, mySecondService.UUID] }];

- (void)peripheralManagerDidStartAdvertising:(CBPeripheralManager *)peripheral
                                       error:(NSError *)error {
 
    if (error) {
        NSLog(@"Error advertising: %@", [error localizedDescription]);
    }
    ...
}

对中心设备的读写请求相应

- (void)peripheralManager:(CBPeripheralManager *)peripheral
    didReceiveReadRequest:(CBATTRequest *)request {
 
    if ([request.characteristic.UUID isEqual:myCharacteristic.UUID]) {
        ...
        if (request.offset > myCharacteristic.value.length) {
            [myPeripheralManager respondToRequest:request
                withResult:CBATTErrorInvalidOffset];
            return;
        }else {
             request.value = [myCharacteristic.value
            subdataWithRange:NSMakeRange(request.offset,
            myCharacteristic.value.length - request.offset)];
        [myPeripheralManager respondToRequest:request withResult:CBATTErrorSuccess];
        }

    }
}

对于写请求，在写代理方法中类似实现方式，修改值使用

myCharacteristic.value = request.value;方法。

对于中心设备注册监听的特征

- (void)peripheralManager:(CBPeripheralManager *)peripheral
                  central:(CBCentral *)central
didSubscribeToCharacteristic:(CBCharacteristic *)characteristic {
 
    NSLog(@"Central subscribed to characteristic %@", characteristic);
    ...
}

NSData *updatedValue = // fetch the characteristic's new value
    BOOL didSendValue = [myPeripheralManager updateValue:updatedValue
        forCharacteristic:characteristic onSubscribedCentrals:nil];//如果用于更新的队列满了，会返回NO，当有队列有空位时会调用peripheralManagerIsReadyToUpdateSubscribers: 方法，你可以在这个方法里重新发送更新数据

其他需要注意的事项：

1.限制广播数据的大小，最大为28byte + 10byte（专用于localNameKey),在广播的字典里，只能传入


CBAdvertisementDataLocalNameKey


and


CBAdvertisementDataServiceUUIDsKey

类型的数据。



2.在不需要时，停止广播


[myPeripheralManager stopAdvertising];

3.对于敏感数据，进行配对验证，对于需要订阅的数据设置，订阅权限。

myCharacteristic = [[CBMutableCharacteristic alloc]
        initWithType:myCharacteristicUUID
        properties:CBCharacteristicPropertyRead | CBCharacteristicPropertyNotify
        value:nil permissions:CBAttributePermissionsReadable];

 emailCharacteristic = [[CBMutableCharacteristic alloc]
        initWithType:emailCharacteristicUUID
        properties:CBCharacteristicPropertyRead
        | CBCharacteristicPropertyNotifyEncryptionRequired
        value:nil permissions:CBAttributePermissionsReadEncryptionRequired];