# CFMessagePort ``` class CFMessagePort ``` ## Overview CFMessagePort objects provide a communications channel that can transmit arbitrary data between multiple threads or processes on the local machine. You create a local message port with [`CFMessagePortCreateLocal(_:_:_:_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateLocal(_:_:_:_:_:)) and make it available to other processes by giving it a name, either when you create it or later with [`CFMessagePortSetName(_:_:)`](/documentation/CoreFoundation/CFMessagePortSetName(_:_:)). Other processes then connect to it using [`CFMessagePortCreateRemote(_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateRemote(_:_:)), specifying the name of the port. To listen for messages, you need to create a run loop source with [`CFMessagePortCreateRunLoopSource(_:_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateRunLoopSource(_:_:_:)) and add it to a run loop with [`CFRunLoopAddSource(_:_:_:)`](/documentation/CoreFoundation/CFRunLoopAddSource(_:_:_:)). > Important: > If you want to tear down the connection, you must invalidate the port (using ``doc://com.apple.corefoundation/documentation/CoreFoundation/CFMessagePortInvalidate(_:)``) before releasing the runloop source and the message port object. Your message port’s callback function will be called when a message arrives. To send data, you store the data in a CFData object and call [`CFMessagePortSendRequest(_:_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFMessagePortSendRequest(_:_:_:_:_:_:_:)). You can optionally have the function wait for a reply and return the reply in another CFData object. Message ports only support communication on the local machine. For network communication, you have to use a [`CFSocket`](/documentation/CoreFoundation/CFSocket) object. ## Topics ### Creating a CFMessagePort Object [`CFMessagePortCreateLocal(_:_:_:_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateLocal(_:_:_:_:_:)) Returns a local CFMessagePort object. [`CFMessagePortCreateRemote(_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateRemote(_:_:)) Returns a CFMessagePort object connected to a remote port. ### Configuring a CFMessagePort Object [`CFMessagePortCreateRunLoopSource(_:_:_:)`](/documentation/CoreFoundation/CFMessagePortCreateRunLoopSource(_:_:_:)) Creates a CFRunLoopSource object for a CFMessagePort object. [`CFMessagePortSetInvalidationCallBack(_:_:)`](/documentation/CoreFoundation/CFMessagePortSetInvalidationCallBack(_:_:)) Sets the callback function invoked when a CFMessagePort object is invalidated. [`CFMessagePortSetName(_:_:)`](/documentation/CoreFoundation/CFMessagePortSetName(_:_:)) Sets the name of a local CFMessagePort object. ### Using a Message Port [`CFMessagePortInvalidate(_:)`](/documentation/CoreFoundation/CFMessagePortInvalidate(_:)) Invalidates a CFMessagePort object, stopping it from receiving or sending any more messages. [`CFMessagePortSendRequest(_:_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFMessagePortSendRequest(_:_:_:_:_:_:_:)) Sends a message to a remote CFMessagePort object. [`CFMessagePortSetDispatchQueue(_:_:)`](/documentation/CoreFoundation/CFMessagePortSetDispatchQueue(_:_:)) Schedules callbacks for the specified message port on the specified dispatch queue. ### Examining a Message Port [`CFMessagePortGetContext(_:_:)`](/documentation/CoreFoundation/CFMessagePortGetContext(_:_:)) Returns the context information for a CFMessagePort object. [`CFMessagePortGetInvalidationCallBack(_:)`](/documentation/CoreFoundation/CFMessagePortGetInvalidationCallBack(_:)) Returns the invalidation callback function for a CFMessagePort object. [`CFMessagePortGetName(_:)`](/documentation/CoreFoundation/CFMessagePortGetName(_:)) Returns the name with which a CFMessagePort object is registered. [`CFMessagePortIsRemote(_:)`](/documentation/CoreFoundation/CFMessagePortIsRemote(_:)) Returns a Boolean value that indicates whether a CFMessagePort object represents a remote port. [`CFMessagePortIsValid(_:)`](/documentation/CoreFoundation/CFMessagePortIsValid(_:)) Returns a Boolean value that indicates whether a CFMessagePort object is valid and able to send or receive messages. ### Getting the CFMessagePort Type ID [`CFMessagePortGetTypeID()`](/documentation/CoreFoundation/CFMessagePortGetTypeID()) Returns the type identifier for the CFMessagePort opaque type. ### Callbacks [`CFMessagePortCallBack`](/documentation/CoreFoundation/CFMessagePortCallBack) Callback invoked to process a message received on a CFMessagePort object. [`CFMessagePortInvalidationCallBack`](/documentation/CoreFoundation/CFMessagePortInvalidationCallBack) Callback invoked when a CFMessagePort object is invalidated. ### Data Types [`CFMessagePortContext`](/documentation/CoreFoundation/CFMessagePortContext) A structure that contains program-defined data and callbacks with which you can configure a CFMessagePort object’s behavior. ### Constants [CFMessagePortSendRequest Error Codes](/documentation/CoreFoundation/1561514-cfmessageportsendrequest-error-c) Error codes for `CFMessagePortSendRequest`. --- 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)