What you need to do in order to use high-level AppleTalk routines depends upon the interfaces you are using. Some differences are outlined below.
MPW before 2.0
When calling the old high-level AppleTalk routines, many programmers get mysterious "resource not found" errors (-192) from such seemingly harmless routines as MPPOpen. The resource that is not being found is `atpl', a resource that contains all the glue code to the high-level routines. In order to use the high-level routines, your application must have this resource in its resource fork. The `atpl' resource is included in a file called "AppleTalk" with any compilers that use this outdated version of the AppleTalk interface.
MPW 2.0 and newer
A newer version of the alternate interfaces is available in MPW 2.0; it includes bug fixes and increased Macintosh II compatibility. With this version of the interface, the `atpl' resource is no longer used. Glue code is now linked into your application.
This will be the final release of the current-style interface. It will be supported for some time as the alternate interface. We have moved to a more straightforward and simple preferred interface, which is also implemented in MPW 2.0 and newer, and is described in the AppleTalk Manager chapter of Inside Macintosh vol. V. Developers are free to continue to use the alternate interface, but in the long run it will be advantageous to move to the preferred interface.
Third Party Compilers
Third party compilers use interfaces that are built from Apple's MPW interfaces. Some compilers may not have upgraded to the new interfaces yet. Contact the individual compiler manufacturers for more information.
Further Reference: