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Inside Macintosh: Networking /

Chapter 6 - AppleTalk Transaction Protocol (ATP) / Using ATP

Canceling an ATP Function

You can cancel all pending ATP function calls made on a specific socket by closing the socket. However, ATP provides functions that allow you to cancel individual function calls or all function calls of a particular kind. If you want to close a socket for which there are still pending requests that you don't want executed, you should first explicitly cancel those requests by using the ATP function provided for this purpose, instead of simply closing the socket.

You can use the following functions to cancel specific requests:

• To cancel a PGetRequest function, use the PKillGetReq function, which is described on page 6-41. You identify the request to be canceled by specifying
  the pointer to the parameter block that you passed to the PGetRequest function
  when you called it.
• To cancel all pending PGetRequest functions on a certain socket, use the ATPKillAllGetReq function described on page 6-42; you specify the socket number, whose pending get requests you want to cancel, as the value of the atpSocket parameter.
• To cancel a PSendRequest or a PNSendRequest function, use the PKillSendReq function described beginning on page 6-38. You identify the request to be canceled
  by specifying the pointer to the parameter block that you passed to the function
  when you issued it. To cancel a PSendRequest function, use the PRelTCB function described beginning on page 6-40. You identify the request to be canceled by specifying the request transaction ID as the transID parameter and the destination socket of the request as the addrBlock parameter.
• To cancel an exactly-once PSendResponse function, use the PRelRspCB function, described beginning on page 6-43. You identify the request to be canceled by specifying the transaction ID of the associated request as the transID parameter and the PSendResponse destination socket number as the atpSocket parameter.