Java Cookbook

Program: Chat Client

This program is a simple Chat program. You can’t break in on ICQ or AIM with it, because they each use their own protocol;^[36] this one simply writes to and reads from a server, locating the server with the applet method getCodeBase( ). The server for this will be presented in Chapter 16. How does it look when you run it? Figure 15-2 shows me chatting all by myself one day.

Figure 15-2. Chat client in action

The code is reasonably self-explanatory. We read from the remote server in a thread to make the input and the output run without blocking each other; this is discussed in Chapter 24. The reading and writing are discussed in this chapter. The program is an applet (see Section 17.3) and is shown in Example 15-11.

Example 15-11. ChatClient.java

import java.applet.*; import java.awt.*; import java.awt.event.*; import java.io.*; import java.net.*; /** Simple Chat Room Applet. * Writing a Chat Room seems to be one of many obligatory rites (or wrongs) * of passage for Java experts these days. * <P> * This one is a toy because it doesn't implement much of a command protocol, which * means we can't query the server as to * who's logged in, * or anything fancy like that. However, it works OK for small groups. * <P> * Uses client socket w/ two Threads (main and one constructed), * one for reading and one for writing. * <P> * Server multiplexes messages back to all clients. ...