(BLE) 无法将数据写入 iOS 上的特性

如何解决(BLE) 无法将数据写入 iOS 上的特性

我一直在开发一个移动应用程序，该应用程序应该向充当 GATT 服务器的 BLE 设备发送一些数据，并在接收到数据后，GATT 服务器发送回通知。

问题是在iOS上，数据没有成功发送，因为GATT服务器没有发送通知。在 Android 上，我在发送数据和接收通知方面没有遇到任何问题。

在 iOS 上，我认为我已经完成了 BLE 连接所需的所有步骤（即服务发现、特征发现、订阅通知、监听回调以确保事件成功发生等），并且我认为问题发生在我将数据写入特征时。

首先，我在Android上做了一个BT snoop日志，分析了一个使用Wireshark的成功案例。

3113    6682.498460 Google_8c:f4:d1 (Pixel 3a)  microchi_16:a6:19 (n08S7E)  ATT 29  ✓   Sent Write Request,Handle: 0x001b (UnkNown: UnkNown)
Frame 3113: 29 bytes on wire (232 bits),29 bytes captured (232 bits)
    Encapsulation type: Bluetooth H4 with linux header (99)
    Arrival Time: May 30,2021 18:01:43.998492000 GTB Daylight Time
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1622386903.998492000 seconds
    [Time delta from prevIoUs captured frame: 0.063883000 seconds]
    [Time delta from prevIoUs displayed frame: 0.063883000 seconds]
    [Time since reference or first frame: 6682.498460000 seconds]
    Frame Number: 3113
    Frame Length: 29 bytes (232 bits)
    Capture Length: 29 bytes (232 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    point-to-point Direction: Sent (0)
    [Protocols in frame: bluetooth:hci_h4:bthci_acl:btl2cap:btatt]
Bluetooth
    [Source: Google_8c:f4:d1 (58:cb:52:8c:f4:d1)]
    [Destination: microchi_16:a6:19 (68:27:19:16:a6:19)]
Bluetooth HCI H4
    [Direction: Sent (0x00)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0111 = Connection Handle: 0x007
    ..00 .... .... .... = PB Flag: First Non-automatically Flushable Packet (0)
    00.. .... .... .... = BC Flag: point-to-point (0)
    Data Total Length: 24
    Data
    [Connect in frame: 3035]
    [disconnect in frame: 3132]
    [Source BD_ADDR: Google_8c:f4:d1 (58:cb:52:8c:f4:d1)]
    [Source Device Name: Pixel 3a]
    [Source Role: UnkNown (0)]
    [Destination BD_ADDR: microchi_16:a6:19 (68:27:19:16:a6:19)]
    [Destination Device Name: n08S7E]
    [Destination Role: UnkNown (0)]
    [Current Mode: UnkNown (-1)]
Bluetooth L2CAP Protocol
    Length: 20
    CID: Attribute Protocol (0x0004)
Bluetooth Attribute Protocol
    Opcode: Write Request (0x12)
    Handle: 0x001b (UnkNown: UnkNown)
    Value: 102120d2451b384fccb055b3b336ac5c36

Data sent from Android

可以看出，值 (102120d2451b384fccb055b3b336ac5c36) 已成功从 Android (char packet_bytes[] = { 0x10,0x21,0x20,0xd2,0x45,0x1b,0x38,0x4f,0xcc,0xb0,0x55,0xb3,0x36,0xac,0x5c,0x36 }).

尝试从 iOS 发送相同的值，我得到以下结果：

let value: [UInt8] = [0x10,0x36]
self.pheripheral?.writeValue(Data(value),for: characteristic,type: .withResponse)

此外，我收到确认值已写入且 didWriteValueFor 特性中没有错误。

我已经使用 PacketLogger 在我的设备上记录了 BT 数据，然后我将其导出并在 Wireshark 中进行了分析。

122 -790273982.464000   localhost ()    microchi_16:a6:19 (n08S7E)  ATT 28  Sent Write Request,Handle: 0x001b (Generic Attribute Profile: Model Number String: Client Characteristic Configuration)
Frame 122: 28 bytes on wire (224 bits),28 bytes captured (224 bits)
Bluetooth
Bluetooth HCI H1 Sent ACL Data
Bluetooth HCI ACL Packet
    .... 0000 0100 0001 = Connection Handle: 0x041
    ..00 .... .... .... = PB Flag: First Non-automatically Flushable Packet (0)
    00.. .... .... .... = BC Flag: point-to-point (0)
    Data Total Length: 24
    Data
    [Connect in frame: 22]
    [disconnect in frame: 138]
    [Source BD_ADDR: 00:00:00_00:00:00 (00:00:00:00:00:00)]
    [Source Device Name: ]
    [Source Role: UnkNown (0)]
    [Destination BD_ADDR: microchi_16:a6:19 (68:27:19:16:a6:19)]
    [Destination Device Name: n08S7E]
    [Destination Role: UnkNown (0)]
    [Current Mode: UnkNown (-1)]
Bluetooth L2CAP Protocol
Bluetooth Attribute Protocol
    Opcode: Write Request (0x12)
        0... .... = Authentication Signature: False
        .0.. .... = Command: False
        ..01 0010 = Method: Write Request (0x12)
    Handle: 0x001b (Generic Attribute Profile: Model Number String: Client Characteristic Configuration)
    Characteristic Configuration Client: 0x2110
        0010 0001 0001 00.. = Reseved: 0x0844
        .... .... .... ..0. = Indication: False
        .... .... .... ...0 = Notification: False
    [Expert Info (Warning/Protocol): Bad Data]

Data sent from iOS

在 iOS 上，Wireshark 显示“错误数据”（与 Android 显示字段“值”不同），当我将鼠标悬停在我发送的数据上时，它会突出显示标题中的 3 个额外字节，而在 Android 上它只突出显示发送的数据。

我尝试了很多方法来发送数据，但是每次从 iOS 发送数据时，Wireshark 都显示“错误数据”。

有没有人遇到过类似的情况？我也不确定为什么 iOS 和 Android 之间的标头不同（iOS 缺少 HCI 数据包类型：ACL 数据标头）。

我要么认为我将数据错误地写入特征（因此“错误数据”显示在 Wireshark 中），要么 GATT 服务器存在问题（这很奇怪，因为它适用于Android 和 Wireshark 只是错误地显示“错误数据”）。

如果我应该包含更多信息，请告诉我。