/** 
 * Nakov Chat Client 
 * (c) Svetlin Nakov, 2002 
 * http://www.nakov.com 
 * 
 * This program is an example from the book "Internet 
 * programming with Java" by Svetlin Nakov. It is freeware. 
 * For more information: http://www.nakov.com/books/inetjava/ 
 */ 
import java.io.*; 
import java.net.*; 
 
/** 
 * NakovChatClient is a client for Nakov Chat Server. After 
 * creating a socket connection to the chat server it starts 
 * two threads. The first one listens for data comming from 
 * the socket and transmits it to the console and the second 
 * one listens for data comming from the console and transmits 
 * it to the socket. After creating the two threads the main 
 * program's thread finishes its execution, but the two data 
 * transmitting threads stay running as long as the socket 
 * connection is not closed. When the socket connection is 
 * closed, the thread that reads it terminates the program 
 * execution. Keep-alive messages are ignored when received. 
 */ 
public class NakovChatClient { 
    public static final String SERVER_HOSTNAME = "localhost"; 
    public static String KEEP_ALIVE_MESSAGE = "!keep-alive"; 
    public static final int SERVER_PORT = 2002; 
 
    private static BufferedReader mSocketReader; 
    private static PrintWriter mSocketWriter; 
 
    public static void main(String[] args) { 
        // Connect to the chat server 
        try { 
            Socket socket = 
                new Socket(SERVER_HOSTNAME, SERVER_PORT); 
            mSocketReader = new BufferedReader(new 
                InputStreamReader(socket.getInputStream())); 
            mSocketWriter = new PrintWriter(new 
                OutputStreamWriter(socket.getOutputStream())); 
            System.out.println("Connected to server " + 
                    SERVER_HOSTNAME + ":" + SERVER_PORT); 
        } catch (IOException ioe) { 
            System.err.println("Can not connect to " + 
                SERVER_HOSTNAME + ":" + SERVER_PORT); 
            ioe.printStackTrace(); 
            System.exit(-1); 
        } 
 
        // Start socket --> console transmitter thread 
        PrintWriter consoleWriter = new PrintWriter(System.out); 
        TextDataTransmitter socketToConsoleTransmitter = new 
            TextDataTransmitter(mSocketReader, consoleWriter); 
        socketToConsoleTransmitter.setDaemon(false); 
        socketToConsoleTransmitter.start(); 
 
        // Start console --> socket transmitter thread 
        BufferedReader consoleReader = new BufferedReader( 
            new InputStreamReader(System.in)); 
        TextDataTransmitter consoleToSocketTransmitter = new 
            TextDataTransmitter(consoleReader, mSocketWriter); 
        consoleToSocketTransmitter.setDaemon(false); 
        consoleToSocketTransmitter.start(); 
    } 
} 
 
/** 
 * Transmits text data from the given reader to given writer 
 * and runs as a separete thread. 
 */ 
class TextDataTransmitter extends Thread { 
    private BufferedReader mReader; 
    private PrintWriter mWriter; 
 
    public TextDataTransmitter(BufferedReader aReader, 
            PrintWriter aWriter) { 
        mReader = aReader; 
        mWriter = aWriter; 
    } 
 
    /** 
     * Until interrupted reads a text line from the reader 
     * and sends it to the writer. 
     */ 
    public void run() { 
        try { 
            while (!isInterrupted()) { 
                String data = mReader.readLine(); 
                if (! data.equals(NakovChatClient. 
                        KEEP_ALIVE_MESSAGE)) { 
                    mWriter.println(data); 
                    mWriter.flush(); 
                } 
            } 
        } catch (IOException ioe) { 
            System.err.println("Lost connection to server."); 
            System.exit(-1); 
        } 
    } 
}