Using CoreBluetooth CBL2CAPChannel to move data

问题

I have set up some data transfer function, using CoreBluetooth CBL2CAPChannel, in a Swift iOS app. Here is the function for sending data:

func sendData(_ outStream: OutputStream) -> Bool {
    let data = tranferBlock! // tranferBlock holds some .utf8 data.
    let bytesWritten = data.withUnsafeBytes {outStream.write($0, maxLength: data.count)}

    if bytesWritten > 0 {
        tranferBlock = nil
        return true
    }

    return false
}

And here is the function for receiving data:

func receiveData(_ inStream: InputStream) {
    let bufLength = 1024
    let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufLength)
    let bytesRead = inStream.read(buffer, maxLength: bufLength)

    if let string = String(bytesNoCopy: buffer,
                           length: bytesRead,
                           encoding: .utf8,
                           freeWhenDone: false) {
        print("READ-L2CAPData:\(bytesRead):\(string)")
        if bytesRead != 0 {
            receiveBuffer = string // receiveBuffer holds the received data.
            let ntfc = NotificationCenter.default
            ntfc.post(name:Notification.Name(rawValue: "DATACAMEIN"),
                      object: nil, userInfo: nil)
        }
    }
}

I can say, it is working, because this allows me to transfer data. But there is one issue: I do not receive data the same way I send it. For example, let us say I send data in 3 packets, like this:

.......
tranferBlock = Data("aaaAAAaaa".utf8)
sendData(outStream)
tranferBlock = Data("bbbBBBbbb".utf8)
sendData(outStream)
tranferBlock = Data("cccCCCccc".utf8)
sendData(outStream)
.......

I would expect, in that case to receive the data in 3 packets, at about the same pace I have sent them:

aaaAAAaaa
bbbBBBbbb
cccCCCccc

But instead I receive one packet:

aaaAAAaaabbbBBBbbbcccCCCccc

And very often, for some reason that I do not know, only when I kill the sending app.

I would like to know what I need to change to receive the data the way I expect.

来源：https://stackoverflow.com/questions/57635965/using-corebluetooth-cbl2capchannel-to-move-data

标签

ios

swift

core-bluetooth

l2cap