CPI-C Starter Set (SAP Library - SAP Communication: CPI-C Programming (BC-CST-GW))

CPI-C Starter Set

Definition

These are the basic functions required for a simple conversation.

Use

Communication between two partner programs via the calls of the CPI-C Starter Set runs as follows:

Establish connection (session/conversation)

Initialization of the communications parameters (via the side information)
Build a logical connection (session):
Start request from the remote transaction program
Both partners are given a conversation ID.

Send/receive information

Send data
Receive data/status messages

Close connection

Close conversation

Structure

The CPI-C Starter Set consists of the following function calls:

Call	Task
CMINIT	Initialize connection
CMALLC	Allocate conversation
CMACCP	Accept conversation
CMSEND	Send data
CMRCV	Receive data
CMDEAL	Deallocate conversation

These functions are all of type CM_RETCODE.

CPI-C works in Two Way Alternate Mode (half-duplex mode).

Only one of the programs has send authorization at any one time. This authorization can be transferred to the partner (status).

The program, which builds communication, has send authorization first.

The send authorization is transferred by transmitting a receipt acknowledgement (CMRCV) in send status. Then, the partner program is authorized to send. Multiple change of communications direction is possible.

The program with the send authorization can call the following functions:

CMSEND Send data
CMRCV from the partner
CMDEAL Close the connection

A side information table with connection parameters must be available in the calling system. CMINIT needs these connection parameters.