HP-UX SNAplus2 R7 APPC Programmer's Guide

Concepts
TP Server API
1.13 APPC and CPI-C
The Common Programming Interface for Communications (CPI-C) application programming interface, another
SNAplus2 API, provides many of the functions of APPC but with a different style of interface.
Where an APPC application sets parameters in a verb control block and then calls a single entry point to APPC
with the address of the block, a CPI-C program calls a different entry point for each verb and passes the required
information as parameters on the call.
Although the programming interfaces for APPC and CPI-C are different, the actual data transmitted between
programs is the same. This means that a CPI-C application can communicate with an APPC TP, just as two APPC
TPs or two CPI-C applications can communicate with each other. The APPC TP does not need to know whether
its partner is an APPC TP or a CPI-C application.
The only restriction on an APPC TP for communications with a CPI-C application is that it must not send Program
Initialization Parameters (PIP data) when allocating the conversation, because CPI-C does not support receiving
PIP data. For more information about PIP data, see the description of the [MC]ALLOCATE verb in Chapter 4,
APPC Conversation Verbs.
1.14 TP Server API
UNIX
The TP server verbs are an extension to the APPC API to allow applications to participate in starting TPs in response
to allocation requests (Attaches).
SNAplus2 provides a default mechanism to start TPs automatically. TPs that can be automatically started are con-
figured in the sna_tps file, as described in the HP-UX SNAplus2 Administration Guide.
Some applications, such as transaction monitors, need more control over starting TPs than this default mechanism
supplies (such as access to the allocation request). The TP server extensions provide the level of support needed
by such applications. For more information about TP servers, see Section 2.12, Writing TP Servers.
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