Inside Macintosh: Networking With Open Transport / Part 2 - Open Transport Reference

Chapter 21 - Providers Reference

Application-Defined Notifier Functions

To receive notice of provider events, you must write and install a notifier function. A notifier function is the callback function that a provider uses to communicate information back to your application for all events affecting a particular provider. A provider in asynchronous mode must have a notifier function to receive completion events.

For most providers, you must also use a notifier function to retrieve asynchronous events. If you have opened an endpoint provider, you can poll for asynchronous events using the OTLook function, but for a mapper provider or a service provider, you cannot poll for asynchronous events; you must use a notifier function instead. In general, it is recommended that you use notifier functions to handle both asynchronous and completion events for all providers.