# CFStreamCreateBoundPair(_:_:_:_:) Creates a bound pair of read and write streams. ``` func CFStreamCreateBoundPair(_ alloc: CFAllocator!, _ readStream: UnsafeMutablePointer?>!, _ writeStream: UnsafeMutablePointer?>!, _ transferBufferSize: CFIndex) ``` ## Parameters `alloc` The allocator to use to allocate memory for the new objects. Pass [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) or `NULL` to use the current default allocator. `readStream` On return, contains a readable stream. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). `writeStream` On return, contains a writable stream. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). `transferBufferSize` The size of the buffer, in bytes, used to transfer data from `readStream` to `writeStream`. ## Discussion The created streams are bound to one another, such that any data written to `writeStream` is received by `readStream`. ## See Also --- 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)