OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual

OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual—522223-001
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Introduction to the GPI
This section provides an overview of the Gateway Programmatic Interface (GPI) and
defines some general concepts and terms used in this manual.
The GPI is an implementation of the X.400 Gateway Application Program Interface as
specified by the X.400 Application Program Interface Association (XAPIA) and the
X/Open Company Limited. This interface enables a client application program to access
the X.400 network through an Open Systems Interconnection/Message Handling System
(OSI/MHS) subsystem. The OSI/MHS subsystem functions as an X.400 message
transfer agent (MTA).
GPI Overview
The GPI service consists of the GPI Procedure Library and the Gateway Interface
Process (GIP). The GPI service and the client program together function as an X.400
gateway enabling the exchange of messages between a proprietary message system and
the X.400 network. Figure 1-1 illustrates the gateway components.
The GPI library procedures can be called from programs written in the Transaction
Application Language (TAL) or the C language. The GPI library procedures translate
messages between the proprietary format and the equivalent X.400 form and manage the
queues used to transfer messages to and from the OSI/MHS MTA.
The gateway is configured as part of the OSI/MHS subsystem. There are two types of
gateway: NORMAL type and P1-EXIT type. For the NORMAL type gateway, routing
decisions are made by the OSI/MHS MTA and the client receives only those messages
bound for the Proprietary Message System. For the P1-EXIT type gateway, the client
program receives messages before the MTA performs routing, optionally makes changes
(such as address adjustment), then optionally transfers them back to the MTA using the
MH-TRANSFER option of the GPI_MT_FINISH_TRANSFER_IN_ procedure.
For a more complete discussion of X.400 networks and the OSI/MHS subsystem, refer
to the OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide and the
OSI/MHS Configuration and Management Manual.
Figure 1-1. GPI Service
101CDT .CDD
GPI
Library
Proprietary
Message
System
X.400 Gateway
Client
GIP
GPI Service
GPI Library Interface
OSI/MHS
MTA