29 service change

　sevice change 特征改变方式

bluetooth 官网：　https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.gatt.service_changed.xml

Core4.2 : (Bluetooth Core Spec V4.2 Vol.3, Part G, 7.1)

(Bluetooth Core Spec V4.2 Vol.3, Part G, 2.5.2)

重要的信息点

Clients without a trusted relationship must perform service discovery on each connection if the server supports the Service Changed characteristic.

A server may set the affected Attribute Handle range to 0x0001 to 0xFFFF to indicate to the client to rediscover the entire set of Attribute Handles on the server.

当service change 的时候 在使用其他的权限的时候 需要首先进行discovery.

The client must perform service discovery before the client uses any service that has an attribute within the affected Attribute Handle range.