The Microsoft® Windows® APPC API extensions allow asynchronous communication within the SNA Server environment and have been designed for Windows 3.x and later versions (with the exception of Windows 3.0 operating in real mode). These extensions provide support for maximum Windows programming compatibility and optimum application performance in both 16-bit and 32-bit operating environments.
The following are the nine Windows APPC extensions: WinAsyncAPPC, WinAsyncAPPCEx, WinAPPCCancelAsyncRequest, WinAPPCCancelBlockingCall, WinAPPCCleanup, WinAPPCIsBlocking, WinAPPCStartup, WinAPPCSetBlockingHook, and WinAPPCUnhookBlockingHook.
Microsoft SNA Server also supports SNA Server-specific extensions to Windows APPC and Common Service Verbs (CSVs). The logical unit (LU) function GetAppcConfig takes a local mode pair and returns the remote LUs that are accessible to the user through that pair. The GetAppcReturnCode and GetCsvReturnCode functions provide a standard set of error strings for use by applications.