swiftxcodesocketsstream

Stream connection not receiving data in Xcode 16

The following code used to work perfectly in Xcode 15. (Release mode)

I was able to receive non-zero data from the stream

self.inputStream?.read(&inputbuffer, maxLength: readsize)

However, after switching to Xcode 16, stream always returns 0. The code hasn't changed at all.

I’ve already tried several things to troubleshoot this:

But none of these made a difference.

private let host = "my host"
private let port = 443
private var inputStream: InputStream?
private var outputStream: OutputStream?

open func connect() {
    
    Stream.getStreamsToHost(withName: host, port: port, inputStream: &self.inputStream, outputStream: &self.outputStream)
    
    if let inputStream = inputStream, let outputStream = outputStream {
        inputStream.delegate = self
        outputStream.delegate = self
        
        CFReadStreamSetDispatchQueue(inputStream, PMMStreamQueue)
        CFWriteStreamSetDispatchQueue(outputStream, PMMStreamQueue)
         
        inputStream.open()
        outputStream.open()
    }
}

func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
    switch eventCode {
    case Stream.Event.endEncountered:
        print("endEncountered")
    case Stream.Event.hasBytesAvailable:
        let readsize = 8192 * 4
        var inputbuffer: [UInt8] = [UInt8](repeating: 0, count: readsize)
        let readBytesCount = self.inputStream?.read(&inputbuffer, maxLength: readsize) ?? 0
        print(readBytesCount)
    default:
        break
    }
}

I'm currently using the Release scheme, and the issue only seems to occur in Release mode under Xcode 16.

Does anyone know how to fix this or what's causing the issue?

Thanks in advance!

Solution

  • ✅ SOLVED!

    The issue was caused by Swift compiler optimizations.

    In Build Settings, under Swift Compiler - Code Generation → Optimization Level,
    select No Optimization [-Onone] instead of any optimized level (like -O or -Osize).

    It seems that enabling optimization affects the behavior of the Stream APIs.
    Once optimizations are disabled, everything works correctly again.