Java Cookbook, 2nd Edition

Chapter 12. Programming External Devices: Serial and Parallel Ports

Introduction

Peripheral devices are usually external to the computer.^[1] Printers, mice, video cameras, scanners, data/fax modems, plotters, robots, telephones, light switches, weather gauges, Personal Digital Assistants (PDAs), and many others exist “out there,” beyond the confines of your desktop or server machine. We need a way to reach out to them.

The Java Communications API not only gives us that but cleverly unifies the programming model for dealing with a range of external devices. It supports both serial (RS232/434, COM, or tty) and parallel (printer, LPT) ports. We’ll cover this in more detail later, but briefly, serial ports are used for modems and occasionally printers, and parallel ports are used for printers and sometimes (in the PC world) for Zip drives and other peripherals.

Before USB (Universal Serial Bus) came along, it seemed that parallel ports would dominate for such peripherals, as manufacturers were starting to make video cameras, scanners, and the like. Now, however, USB has become the main attachment mode for such devices. A Java Standards Request (JSR) is in the works to build a standard API for accessing USB devices under Java, but it has not progressed to the release stage. A reference implementation can be downloaded from http://sourceforge.net/projects/javax-usb. A competing Java API for USB can be found at http://jusb.sourceforge.net. Since the JSR is not completed, I do not document ...