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Chapter 5 - AppleTalk Data Stream Protocol (ADSP) / About ADSP

Unsolicited ADSP Events

After you open a connection, you can receive events that are not generated in response to any of the ADSP calls that your application makes. The other connection end or ADSP initiates these events. For example, the remote connection end can send you an attention message or a forward reset.

You receive a forward reset event when the remote connection end cancels delivery of all outstanding data to your connection end. A forward reset causes ADSP to discard all data in the send queue, all data in transit to the remote connection end, and all data in the remote connection end's receive queue that the client has not yet read.

The remote connection end can close the connection, and this, too, will generate an event notification for your connection end. You also receive event notification when ADSP tears down a connection because the remote end has become unreachable.

ADSP sets the bits of your connection end's connection control block user flags field to identify the type of event. For more information about this field, see "Creating and Using a Connection Control Block" on page 5-12. You can provide a user routine that ADSP is to call whenever you receive one of these events. This user routine is similar in concept and use to an ioCompletion routine that many of the other AppleTalk protocols use. See "Writing a User Routine for Connection Events" on page 5-26 for information on how to write a user routine.