An abstract class that represents a communication channel.
SDKs
- iOS 2.0+
- macOS 10.0+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
Framework
- Foundation
Declaration
class Port : NSObject
Overview
Communication occurs between Port objects, which typically reside in different threads or tasks. The distributed objects system uses Port objects to send Port objects back and forth. Implement interapplication communication using distributed objects whenever possible and use Port objects only when necessary.
To receive incoming messages, Port objects must be added to an Run object as input sources. NSConnection objects automatically add their receive port when initialized.
When an Port object receives a port message, it forwards the message to its delegate in a handle or handle(_:) message. The delegate should implement only one of these methods to process the incoming message in whatever form desired. handle provides a message as a raw Mach message beginning with a msg structure. handle(_:) provides a message as an Port object, which is an object-oriented wrapper for a Mach message. If a delegate has not been set, the NSPort object handles the message itself.
When you are finished using a port object, you must explicitly invalidate the port object prior to sending it a release message. Similarly, if your application uses garbage collection, you must invalidate the port object before removing any strong references to it. If you do not invalidate the port, the resulting port object may linger and create a memory leak. To invalidate the port object, invoke its invalidate() method.
Foundation defines three concrete subclasses of NSPort. NSMach and Message allow local (on the same machine) communication only. Socket allows for both local and remote communication, but may be more expensive than the others for the local case. When creating an NSPort object, using alloc or port, an NSMach object is created instead.