iOS - Sending and receiving data simultaneously - ios

Question

thanks for taking the time to read my question.
Basically I'm connecting to another device using MultipeerConnectivity and I want to stream data to the other device while receiving data.
My issue is that one of the devices ends up only sending data, and the other device ends up only receiving it.
Here is my sending method. This method is a delegate method from AVCaptureAudioDataOutputSampleBufferDelegate so it is automatically called.
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
//-------------------------------------------------------
// Writing to output stream
var blockBuffer: CMBlockBuffer?
var audioBufferList: AudioBufferList = AudioBufferList.init()
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, nil, &audioBufferList, MemoryLayout<AudioBufferList>.size, nil, nil, kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment, &blockBuffer)
let buffers = UnsafeMutableAudioBufferListPointer(&audioBufferList)
for buffer in buffers {
let u8ptr = buffer.mData!.assumingMemoryBound(to: UInt8.self)
let output = outputStream!.write(u8ptr, maxLength: Int(buffer.mDataByteSize))
if (output == -1) {
let error = outputStream?.streamError
print("\(#file) > \(#function) > Error on outputStream: \(error!.localizedDescription)")
}
else {
print("\(#file) > \(#function) > Data sent")
}
}
}
And here is my receiving method (I do handle other stream events they are just irrelevant here). You can ignore all of the audio related stuff, it doesn't work right now, but it's not my main issue. This method is a delegate of OutputStream, so it is also automatically called when data is available from the stream.
func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
case Stream.Event.hasBytesAvailable:
print("\(#file) > \(#function) > New data has arrived")
readFromStream()
}
func readFromStream() {
while (inputStream!.hasBytesAvailable) {
var buffer = [UInt8](repeating: 0, count: 4096)
let length = inputStream!.read(&buffer, maxLength: buffer.count)
if (length > 0) {
if (audioEngine!.isRunning) {
print("\(#file) > \(#function) > audioEngine is running")
audioEngine!.stop()
audioEngine!.reset()
}
else {
print("\(#file) > \(#function) > audioEngine is NOT running")
}
print("\(#file) > \(#function) > \(length) bytes read")
let audioBuffer = bytesToAudioBuffer(buffer)
let mainMixer = audioEngine!.mainMixerNode
audioEngine!.connect(audioPlayer!, to: mainMixer, format: audioBuffer.format)
audioPlayer!.scheduleBuffer(audioBuffer, completionHandler: nil)
do {
try audioEngine!.start()
}
catch let error as NSError {
print("\(#file) > \(#function) > error: \(error.localizedDescription)")
}
audioPlayer!.play()
}
}
}
From these two methods you can see I have print statements for when data comes in and when data is being sent out. On one of the devices I end up consistently reading data and never sending any, and on the other device I end up constantly sending data and never receiving any.
I imagine this is because I'm not using threads.. But I've never worked with threads on iOS. If this is the case, can anyone guide me on how to do so?
If you need any more information please let me know.

Answer 1

Eventually I did figure out a feasible way to use threads:
let streamReceiverQueue = DispatchQueue(label: "newQueue", qos: DispatchQoS.userInteractive)
streamReceiverQueue.sync {
// code here
}
streamReceiverQueue.async {
// code here
}