Java I/O

Chapter 17. The Java Communications API

This chapter covers the Java Communications API 2.0, a standard extension available in Java 1.1 and later that allows Java applications (but not applets) to send and receive data to and from the serial and parallel ports of the host computer. The Java Communications API allows Java programs to communicate with essentially any device connected to a serial or parallel port, like a printer, a scanner, a modem, a tape backup unit, and so on. The Comm API operates at a very low level. It only understands how to send and receive bytes to these ports. It does not understand anything about what these bytes mean. Doing useful work generally requires not only understanding the Java Communications API (which is actually quite simple) but also the protocols spoken by the devices connected to the ports (which can be almost arbitrarily complex).

The Architecture of the Java Communications API

Because the Java Communications API is a standard extension, it is not installed by default with the JDK. You have to download it from http://java.sun.com/products/javacomm/index.html and install it separately.

Note

This chapter is based on the first beta of the Java Communications API. It is almost certain that some parts of this chapter will become inaccurate by the time you read this. Indeed, throughout the process of writing this chapter, I identified a number of bugs and inconsistencies that I forwarded to Sun. They even fixed a few in between early access 3 and ...