HP X.25/9000 Programmer's Guide

Chapter 1 5

Introduction to X.25 Programmatic Access

Using BSD IPC

BSD IPC is a set of program development tools for interprocess

communication. HP's implementation of BSD IPC is a subset of the

networking services originally developed by the University of California

at Berkeley. Before you attempt to use BSD IPC, you must be familiar

with the C programming language.

The BSD IPC tools let you create distributed applications that pass data

between processes (on the same computer or on different computers

connected by a network) without requiring a complete understanding of

the many layers of networking protocols. This is done using a set of

system calls. These system calls, when used in the correct sequence, let

you create communication endpoints called sockets and transfer data

between them.

You will also ﬁnd a description here of the steps involved in establishing

and using X.25 programmatic access through BSD IPC connections. This

manual describes the protocols you must use and how the BSD IPC

system calls interact.

The library routines and system calls that you need to implement a BSD

IPC application are described throughout this manual.

You do not need to specify any special libraries when linking to use BSD

IPC over X.25. All required library routines are in the common C library

(libc.a). The compiler uses libc.a automatically.

Details of each system call are described in the Section 2 entries of your

man pages.

Using BSD IPC and X.25 With the Client/Server Model

In order to run X.25 applications over BSD IPC, two separate application

processes must be running at both ends of a VC. The example below

shows a typical client/server sequence (at the X.25 level) for BSD/X.25

communications. In this example, a CALL REQUEST packet is sent to

the server. The server receives a CALL INDICATION packet and accepts

the call by sending a CALL_ACCEPTED packet.

1. The client process requests a connection by sending a CALL

REQUEST packet.

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