APPC is a general application protocol for communication between any two programs in an SNA environment. It can be used to deliver data in substantially one direction-such as a file transfer. It can be used for a complicated dialog-such as a terminal to application datastream. However, it can be easily adapted to implement communication along the client/server processing model.
The usual model of client/server processing is that there are potentially many clients, and usually a smaller number of servers, in a distributed processing environment. The clients request information and they are served that information by a server. A simple question, followed by one or more related responses, is an example of this approach, however the actual dialog could be more complicated.
Ideally the client does not nominate the server, but merely requests a particular type of service, and depending upon configuration options, the transaction will be directed to an appropriate server for processing.