XPC Resources

XPC is the preferred inter-process communication (IPC) mechanism on Apple platforms. XPC has three APIs:

• The high-level NSXPCConnection API, for Objective-C and Swift
• The low-level Swift API, introduced with macOS 14
• The low-level C API, which, while callable from all languages, works best with C-based languages

General:

• Forums subtopic: App & System Services > Processes & Concurrency
• Forums tag: XPC
• Creating XPC services documentation
• NSXPCConnection class documentation
• Low-level API documentation
• XPC has extensive man pages — For the low-level API, start with the xpc man page; this is the original source for the XPC C API documentation and still contains titbits that you can’t find elsewhere. Also read the xpcservice.plist man page, which documents the property list format used by XPC services.
• Daemons and Services Programming Guide archived documentation
• WWDC 2012 Session 241 Cocoa Interprocess Communication with XPC — This is no longer available from the Apple Developer website )-:
• Technote 2083 Daemons and Agents — It hasn’t been updated in… well… decades, but it’s still remarkably relevant.
• TN3113 Testing and Debugging XPC Code With an Anonymous Listener
• XPC and App-to-App Communication forums post
• Validating Signature Of XPC Process forums post
• This forums post summarises the options for bidirectional communication

Related tags include:

• Inter-process communication, for other IPC mechanisms
• Service Management, for installing and uninstalling Service Management login items, launchd agents, and launchd daemons

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
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