# CFNetDiagnosticCreateWithStreams(_:_:_:) Creates a network diagnostic object from a pair of CFStreams. ``` func CFNetDiagnosticCreateWithStreams(_ alloc: CFAllocator?, _ readStream: CFReadStream?, _ writeStream: CFWriteStream?) -> Unmanaged ``` ## Parameters `alloc` The allocator to use to allocate memory for the new object. Pass `NULL` or kCFAllocatorDefault to use the current default allocator. `readStream` Reference to a read stream whose connection has failed, or `NULL` if you do not want the CFNetDiagnosticRef to have a read stream. `writeStream` Reference to a write stream whose connection has failed, or `NULL` if you do not want the CFNetDiagnosticRef to have a write stream. ## Discussion This function uses references to a read steam and a write stream (or just a read stream or just a write stream) to create a reference to an instance of a CFNetDiagnostic object. You can pass the reference to [`CFNetDiagnosticDiagnoseProblemInteractively(_:)`](/documentation/CFNetwork/CFNetDiagnosticDiagnoseProblemInteractively(_:)) to open a Network Diagnostics window or to [`CFNetDiagnosticCopyNetworkStatusPassively(_:_:)`](/documentation/CFNetwork/CFNetDiagnosticCopyNetworkStatusPassively(_:_:)) to get a description of the connection referenced by `readStream` and `writeStream`. ### Special Considerations This function is thread safe as long as another thread does not alter the same CFNetDiagnosticRef at the same time. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)