ULTRIX Guide tc the X/Open Transport interface

This document, the "ULTRIX Guide to the X/Open Transport Interface," published by Digital Equipment Corporation in June 1990, is a programming manual for experienced C programmers who want to write network applications on the ULTRIX operating system using the X/Open Transport Interface (XTI).

The guide details how to develop network applications using XTI system calls and subroutines, covering its two primary service modes:

1. Connection-Mode: For reliable, sequenced data transfer over established virtual circuits (e.g., TCP), outlining phases like initialization, connection establishment, data transfer, connection release, and deinitialization.
2. Connectionless-Mode: For short-term, self-contained message exchanges (e.g., UDP), detailing its initialization, data transfer, and deinitialization phases.

It highlights XTI's enhancements over traditional BSD socket-based interprocess communication, such as improved application portability, advanced event management, and the ability for multiple processes to share transport endpoints. The manual also includes advanced topics like managing transport characteristics, memory resources, execution modes (synchronous and asynchronous), and error reporting. A significant portion is dedicated to guiding programmers in migrating existing socket-based software to XTI-based applications. Comprehensive programming examples are provided for both connection-mode (client/server) and connectionless-mode (transaction server), along with state transition tables for XTI events and functions.