# CFStreamCreatePairWithSocket(_:_:_:_:) Creates readable and writable streams connected to a socket. ``` func CFStreamCreatePairWithSocket(_ alloc: CFAllocator!, _ sock: CFSocketNativeHandle, _ readStream: UnsafeMutablePointer?>!, _ writeStream: UnsafeMutablePointer?>!) ``` ## Parameters `alloc` The allocator to use to allocate memory for the new objects. Pass `NULL` or [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) to use the current default allocator. `sock` The pre-existing (and already connected) socket which the socket streams should use. > Important: > By default, your app is responsible for closing this socket after you close both streams. If you want CFNetwork to take ownership of the socket, set the ``doc://com.apple.corefoundation/documentation/CoreFoundation/kCFStreamPropertyShouldCloseNativeSocket`` property of the stream to ``doc://com.apple.corefoundation/documentation/CoreFoundation/kCFBooleanTrue``. `readStream` Upon return, a readable stream connected to the socket address in `signature`. If you pass `NULL`, this function will not create 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` Upon return, a writable stream connected to the socket address in `signature`. If you pass `NULL`, this function will not create 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). ## Discussion Most properties are shared by both streams. Setting a shared property for one stream automatically sets the property for the other. --- 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)