Server-Side Java - Java - page 676

}

}

Program: A Java Chat Server

This program implements a simple chat server (see Example 16-16 ) that works with the chat
client program from Program: Chat Client . It accepts connections from an arbitrary number
of clients; any message sent from one client is broadcast to all clients. In addition to Server-
Socket s, it demonstrates the use of threads (see Chapter 22 ). Because there are interactions
among clients, this server needs to keep track of all the clients it has at any one time. I use an
ArrayList (see Like an Array, but More Dynamic ) to serve as an expandable list and am
careful to use the synchronized keyword around all accesses to this list to prevent one
thread from accessing it while another is modifying it (this is discussed in Chapter 22 ) .

Example 16-16. ChatServer.java
public public class ChatServer {

/** What I call myself in system messages */
protected

class ChatServer

protected final static String CHATMASTER_ID = "ChatMaster" ;

/** What goes between any handle and the message */
protected

final static

protected final static String SEP = ": " ;

/** The Server Socket */
protected

final static

protected ServerSocket servSock ;
/** The list of my current clients */
protected protected List < ChatHandler > clients ;

/** Debugging state */
private private static static boolean boolean DEBUG = false false ;

/** Main just constructs a ChatServer, which should never return */
public public static throws IOException {

System . out . println ( "DarwinSys ChatServer 0.1 starting..." );
iif ( argv . length == 1 && argv [ 0 ]. equals ( "-debug" ))
DEBUG = true

static void void main ( String [] argv ) throws

true ;
ChatServer w = new new ChatServer ();

w . runServer (); // should never return.
System . out . println ( "**ERROR* ChatServer 0.1 quitting" );

}

/** Construct (and run!) a Chat Service
* @throws IOException
*/
ChatServer () throws throws IOException {

clients = new new ArrayList <>();