ios - 如何通过 CBL2CAPChannel 发送和接收数据

Question

我正在尝试在 2 个 iOS 设备之间打开一个 L2CAP channel 并双向传输数据。其中一个设备充当中央设备，另一个设备充当外围设备。

外围方面:

我像这样发布一个 L2CAPChannel:

func peripheralManagerDidUpdateState(_ peripheral: CBPeripheralManager) {
    if peripheral.state == .poweredOn {
        peripheral.publishL2CAPChannel(withEncryption: false)
    }
}

为加密尝试了 true 和 false。

然后， channel 发布后，我从 didPublishL2CAPChannel 委托(delegate)方法中获取 PSM，并创建一个具有包含 PSM 值的特征的服务，并开始对其进行广告。

在中央一侧:

我扫描外围设备，找到合适的设备，连接到它，开始发现服务，一旦发现服务，我就会发现特征。我找到特征，读取它的值并获得 PSM。然后我这样做:

self.peripheral.openL2CAPChannel(psm)

然后我在 channel 已打开的委托(delegate)方法中收到回调并执行此操作:

func peripheral(_ peripheral: CBPeripheral, didOpen channel: CBL2CAPChannel?, error: Error?) {
    guard error == nil else {
        print("Couldn't open channel. Error: \(error!.localizedDescription)")
        return
    }
    self.l2capChannel = channel
    self.l2capChannel?.inputStream.delegate = self
    self.l2capChannel?.outputStream.delegate = self
    print("L2CAP channel opened with \(peripheral.name ?? "unknown")")
}

这打印:

L2CAP channel opened with mrsta’s iPad

再次在外围方面:

我在委托(delegate)方法中得到回调:

func peripheralManager(_ peripheral: CBPeripheralManager, didOpen channel: CBL2CAPChannel?, error: Error?) {
    guard error == nil else {
        print("Couldn't open channel. Error: \(error!.localizedDescription)")
        return
    }
    self.l2capChannel = channel
    self.l2capChannel?.inputStream.delegate = self
    self.l2capChannel?.outputStream.delegate = self
    print("L2CAP channel opened")
}

这打印:

[CoreBluetooth] No central present! Creating a new object. This shouldn't happen.
L2CAP channel opened

到目前为止， channel 似乎在两侧都打开了。我只是想知道上面打印的消息是什么“......没有中央礼物!......”

一段时间后，我开始在控制台中收到这样的消息:

[CoreBluetooth] WARNING: Unknown error: 436
[CoreBluetooth] No known channel matching peer <CBPeripheral: 0x2829de120, identifier = 241BAA6F-0BFD-9F5A-1EC9-35A4FD246DF5, name = mrsta’s iPad, state = connected> with psm 192
[CoreBluetooth] WARNING: Unknown error: 431

我不知道这些是什么意思。有什么建议吗？

我还在两边都实现了 StreamDelegate 方法:

func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
    print("Stream Event occurred: \(eventCode)")
    if eventCode == .hasSpaceAvailable {
        self.tryToWrite()
    }
}

但是上面的委托(delegate)方法永远不会被调用。我尝试像这样写入输出流(从中央端的 didOpen channel 委托(delegate)方法调用的 tryToWrite):

func tryToWrite() {
    let string = "Hello"
    let stringData = Data(from: string)
    let _ = stringData.withUnsafeBytes { write(stuff: $0, to: self.l2capChannel, withMaxLength: stringData.count) }
}

func write(stuff: UnsafePointer<UInt8>, to channel: CBL2CAPChannel?, withMaxLength maxLength: Int) {
    let result = channel?.outputStream.write(stuff, maxLength: maxLength)
    print("Write result: \(String(describing: result))")
}

结果是:

Write result: Optional(-1)

根据文档，这意味着写入失败。

请告诉我我错过了什么？打开 channel 后出现的错误是什么？写入和读取数据的正确方法是什么？

Answer 1

我使用 L2CAP，它正在运行。我在两个“didOpen”函数中所做的是

self.l2capChannel = channel

self.l2capChannel?.inputStream.delegate = self 
self.l2capChannel?.inputStream.schedule(in: .main, forMode: .defaultRunLoopMode)
self.l2capChannel?.inputStream.open()

self.l2capChannel?.outputStream.delegate = self
self.l2capChannel?.outputStream.schedule(in: .main, forMode: .defaultRunLoopMode)
self.l2capChannel?.outputStream.open()

当我不再需要它们时，我会关闭它们

self.l2capChannel?.inputStream.close()
self.l2capChannel?.inputStream.remove(from: .main, forMode: .defaultRunLoopMode)

self.l2capChannel?.outputStream.close()
self.l2capChannel?.outputStream.remove(from: .main, forMode: .defaultRunLoopMode)

self.l2capChannel? = nil