Rather than sending an IOSurfaceRef, send an IOSurface *: - (void)sendFrame:(IOSurface *)frame; IOSurfaceRef is toll-free bridged to IOSurface *, so all you need to do is cast to IOSurface * and it should work. This is true of other CF-types. Objective-C types (NSString, NSDictionary, etc.) work via NSXPCConnection but their corresponding CF-types (CFStringRef, CFDictionaryRef, etc.) don't.