APPC allows interconnected systems to communicate and share the processing of applications. You can use APPC services to share processing between applications running on one of the following systems:

The implementation of your application's connection will differ depending on which of these target systems your application is running.

Regardless of the target system, your application will start (allocate) an APPC conversation by issuing an allocate call that contains specific information, such as the name of the partner transaction program (TP), the logical unit (LU) in the network where the TP resides, and other network and security information. The conversation is established when the partner TP accepts the conversation. After a conversation is established, other calls can transfer and receive data until a TP ends (deallocates) the conversation with a deallocate call.

This chapter focuses on some of the basic concepts of building APPC applications by building both a client (front-end) and server (back-end) application. The client and server applications will exchange string data. These applications are provided in the following sections:

Note that, even though this chapter focuses on writing Smalltalk code for APPC applications, you can use APPC nonvisual parts in your server applications.