Client-Server side GUI programming

Question

I want to create a client-server side gui programming with java
i read this web adress
http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html
for information but there are some parts that i didnt understand and wait for your help
i m trying to build an online-help(live chat) system so when people press the start chat button a java page will appear but i wonder how this will connect to the person who is on server side
i mean is it possible to 2 users connect the same port and chat with each other
I mean when user press the chat button the online help supporter will be informed somebody wants to speak with him and they will start a chat
how can i do something like that
any help would be usefull thanks

Answer 1

Below is an example of a client/server program.
It shows how the server listens for multiple clients.
* TriviaServerMulti.java
* Created on May 12, 2005
package server;
* @author johnz
import java.io.*;
import java.net.*;
import java.util.Random;
* This TriviaServer can handle multiple clientSockets simultaneously
* This is accomplished by:
* - listening for incoming clientSocket request in endless loop
* - spawning a new TriviaServer for each incoming request
* Client connects to server with:
* telnet <ip_address> <port>
*     <ip_address> = IP address of server
*  <port> = port of server
* In this case the port is 4413 , but server can listen on any port
* If server runs on the same PC as client use IP_addess = localhost
* The server reads file
* Note: a production server needs to handle start, stop and status commands
public class TriviaServerMulti implements Runnable {
    // Class variables
    private static final int WAIT_FOR_CLIENT = 0;
    private static final int WAIT_FOR_ANSWER = 1;
    private static final int WAIT_FOR_CONFIRM = 2;
    private static String[] questions;
    private static String[] answers;
    private static int numQuestions;
    // Instance variables
    private int num = 0;
    private int state = WAIT_FOR_CLIENT;
    private Random rand = new Random();
    private Socket clientSocket = null;
    public TriviaServerMulti(Socket clientSocket) {
        //super("TriviaServer");
        this.clientSocket = clientSocket;
    public void run() {
        // Ask trivia questions until client replies "N"
        while (true) {
            // Process questions and answers
            try {
                InputStreamReader isr = new InputStreamReader(clientSocket.getInputStream());
                BufferedReader is = new BufferedReader(isr);
//                PrintWriter os = new PrintWriter(new
//                   BufferedOutputStream(clientSocket.getOutputStream()), false);
                PrintWriter os = new PrintWriter(clientSocket.getOutputStream());
                String outLine;
                // Output server request
                outLine = processInput(null);
                os.println(outLine);
                os.flush();
                // Process and output user input
                while (true) {
                    String inLine = is.readLine();
                    if (inLine.length() > 0)
                        outLine = processInput(inLine);
                    else
                        outLine = processInput("");
                    os.println(outLine);
                    os.flush();
                    if (outLine.equals("Bye."))
                        break;
                // Clean up
                os.close();
                is.close();
                clientSocket.close();
                return;
            } catch (Exception e) {
                System.err.println("Error: " + e);
                e.printStackTrace();
    private String processInput(String inStr) {
        String outStr = null;
        switch (state) {
            case WAIT_FOR_CLIENT:
                // Ask a question
                outStr = questions[num];
                state = WAIT_FOR_ANSWER;
                break;
            case WAIT_FOR_ANSWER:
                // Check the answer
                if (inStr.equalsIgnoreCase(answers[num]))
                    outStr="\015\012That's correct! Want another (y/n)?";
                else
                    outStr="\015\012Wrong, the correct answer is "
                        + answers[num] +". Want another (y/n)?";
                state = WAIT_FOR_CONFIRM;
                break;
            case WAIT_FOR_CONFIRM:
                // See if they want another question
                if (!inStr.equalsIgnoreCase("N")) {
                    num = Math.abs(rand.nextInt()) % questions.length;
                    outStr = questions[num];
                    state = WAIT_FOR_ANSWER;
                } else {
                    outStr = "Bye.";
                    state = WAIT_FOR_CLIENT;
                break;
        return outStr;
    private static boolean loadData() {
        try {
            //File inFile = new File("qna.txt");
            File inFile = new File("data/qna.txt");
            FileInputStream inStream = new FileInputStream(inFile);
            byte[] data = new byte[(int)inFile.length()];
            // Read questions and answers into a byte array
            if (inStream.read(data) <= 0) {
                System.err.println("Error: couldn't read q&a.");
                return false;
            // See how many question/answer pairs there are
            for (int i = 0; i < data.length; i++)
                if (data[i] == (byte)'#')
                    numQuestions++;
            numQuestions /= 2;
            questions = new String[numQuestions];
            answers = new String[numQuestions];
            // Parse questions and answers into String arrays
            int start = 0, index = 0;
               String LineDelimiter = System.getProperty("line.separator");
               int len = 1 + LineDelimiter.length(); // # + line delimiter
            boolean isQuestion = true;
            for (int i = 0; i < data.length; i++)
                if (data[i] == (byte)'#') {
                    if (isQuestion) {
                        questions[index] = new String(data, start, i - start);
                        isQuestion = false;
                    } else {
                        answers[index] = new String(data, start, i - start);
                        isQuestion = true;
                        index++;
                start = i + len;
        } catch (FileNotFoundException e) {
            System.err.println("Exception: couldn't find the Q&A file.");
            return false;
        } catch (IOException e) {
            System.err.println("Exception: couldn't read the Q&A file.");
            return false;
        return true;
    public static void main(String[] arguments) {
        // Initialize the question and answer data
        if (!loadData()) {
            System.err.println("Error: couldn't initialize Q&A data.");
            return;
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(4413);
            System.out.println("TriviaServer up and running ...");
        } catch (IOException e) {
            System.err.println("Error: couldn't create ServerSocket.");
            System.exit(1);
        Socket clientSocket = null;
        // Endless loop: waiting for incoming client request
        while (true) {
            // Wait for a clientSocket
            try {
                clientSocket = serverSocket.accept();   // ServerSocket returns a client socket when client connects
            } catch (IOException e) {
                System.err.println("Error: couldn't connect to clientSocket.");
                System.exit(1);
            // Create a thread for each incoming request
            TriviaServerMulti server = new TriviaServerMulti(clientSocket);
            Thread thread = new Thread(server);
            thread.start(); // Starts new thread. Thread invokes run() method of server.
}This is the text file:
Which one of the Smothers Brothers did Bill Cosby once punch out?
(a) Dick
(b) Tommy
(c) both#
b#
What's the nickname of Dallas Cowboys fullback Daryl Johnston?
(a) caribou
(b) moose
(c) elk#
b#
What is triskaidekaphobia?
(a) fear of tricycles
(b) fear of the number 13
(c) fear of kaleidoscopes#
b#
What southern state is most likely to have an earthquake?
(a) Florida
(b) Arkansas
(c) South Carolina#
c#
Which person at Sun Microsystems came up with the name Java in early 1995?
(a) James Gosling
(b) Kim Polese
(c) Alan Baratz#
b#
Which figure skater is the sister of Growing Pains star Joanna Kerns?
(a) Dorothy Hamill
(b) Katarina Witt
(c) Donna De Varona#
c#
When this Old Man plays four, what does he play knick-knack on?
(a) His shoe
(b) His door
(c) His knee#
b#
What National Hockey League team once played as the Winnipeg Jets?
(a) The Phoenix Coyotes
(b) The Florida Panthers
(c) The Colorado Avalanche#
a#
David Letterman uses the stage name "Earl Hofert" when he appears in movies. Who is Earl?
(a) A crew member on his show
(b) His grandfather
(c) A character on Green Acres#
b#
Who created Superman?
(a) Bob Kane
(b) Jerome Siegel and Joe Shuster
(c) Stan Lee and Jack Kirby#
b#