MultitClient Server - Allowing Constant communication

Question

I am trying to build a small chat server between two clients. I am using Threads for each client.

I am able to send one message front and back, but then everything turns to sh*t.

Here is the code:

Server class

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;

import javax.swing.*;


public class Server extends JFrame{

private JTextField userText;
private JTextArea chatWindow;
private ObjectOutputStream output;
private ObjectInputStream input;
private ServerSocket server;
private static Socket connection = null;
private String message;
private String message2;
private static final int maxClientsCount = 10;
private static final clientThread[] threads = new clientThread[maxClientsCount];
int counter = 0;

//constructor
public Server(){
    super("Server");
    userText = new JTextField();
    userText.setEditable(false);
    add(userText, BorderLayout.NORTH);
    chatWindow = new JTextArea();
    add(new JScrollPane(chatWindow));
    setSize(300,150);
    setVisible(true);
}

//set up and run the server
public void startRunning(){
    try{
        server = new ServerSocket(6789, 100);
        while(true){
            try{
                waitForConnection();
                //               setupStreams();
                //               whileChatting();
            }catch(EOFException eofException){
                showMessage("\n Server ended the connection! ");
            }finally{
                closeConnection();
            }
        }
    }catch(IOException ioException){
        ioException.printStackTrace();
    }
}

//wait for connection, then display connection information
private void waitForConnection() throws IOException{
    while (true) {
        try {
            connection = server.accept();
            int i = 0;
            for (i = 0; i < maxClientsCount; i++) {
                if (threads[i] == null) {
                    (threads[i] = new clientThread(connection, threads)).start();
                    showMessage("heehehehe");
                    counter++;
                    break;
                }
            }
            if (i == maxClientsCount) {
                connection.close();
            }
        } catch (IOException e) {
            System.out.println(e);
        }
    }
}


//close streams and sockets after you are done chatting
private void closeConnection(){
    showMessage("\n Closing connections... \n");
    ableToType(false);
    try{
        output.close();
        input.close();
        connection.close();
    }catch(IOException ioException){
        ioException.printStackTrace();
    }
}

private void showMessage(final String text){
    SwingUtilities.invokeLater(
            new Runnable(){
                public void run(){
                    chatWindow.append(text);
                }
            }
            );
}

//let the user type stuff into their box
private void ableToType(final boolean tof){
    SwingUtilities.invokeLater(
            new Runnable(){
                public void run(){
                    userText.setEditable(tof);
                }
            }
            );
}

}


class clientThread extends Thread {

private String clientName = null;
private ObjectInputStream is = null;
private ObjectOutputStream os = null;
private Socket clientSocket = null;
private final clientThread[] threads;
private int maxClientsCount;

public clientThread(Socket clientSocket, clientThread[] threads) {
    this.clientSocket = clientSocket;
    this.threads = threads;
    maxClientsCount = threads.length;
}

public void run()  {
    int maxClientsCount = this.maxClientsCount;
    clientThread[] threads = this.threads;
    try {

        is = new ObjectInputStream(clientSocket.getInputStream());
        os = new ObjectOutputStream(clientSocket.getOutputStream());

        while (true) {
            String message = (String)is.readObject();
            for (int i = 0; i < maxClientsCount; i++) {
                if (threads[i] != null ) {
                        threads[i].os.writeObject(message);

                }
            }
            for (int i = 0; i < maxClientsCount; i++) {
                if (threads[i] == this) {
                    threads[i] = null;
                }
            }

        }
    } catch (IOException | ClassNotFoundException e) {
    }
}
}

Client class:

package Client;

import java.io.*;
import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

import java.net.*;

public class Client extends JFrame implements Runnable{

private JTextField userText;
private JTextArea chatWindow;
private ObjectOutputStream output;
private ObjectInputStream input;
private String message = "";
private String serverIP;
private Socket connection;
private JButton button = new JButton("Image");

//Constructor

public Client(String host){
    super("PHONE");
    this.serverIP = host;
    userText = new JTextField();
    userText.setEditable(false);
    userText.addActionListener(
            new ActionListener(){
                public void actionPerformed(ActionEvent event){
                    sendMessage(event.getActionCommand());
                    userText.setText("");
                }
            }
            );
    add(userText, BorderLayout.NORTH);
    chatWindow = new JTextArea();
    chatWindow.setSize(new Dimension(100,200));
    add(new JScrollPane(chatWindow), BorderLayout.CENTER);
    add(button, BorderLayout.SOUTH);
    setSize(300,150);
    setVisible(true);
}

//connect to server

public void startRunning(){
    try {
        connectToServer();
        setupStream();
        //              whileChatting();
        receiveMessage();
    } catch (EOFException eofException) {
        showMessage("\n Client terminated connection");

        // TODO: handle exception
    }catch(IOException ioException){
        ioException.printStackTrace();
    }
}

//connect to a server

private void connectToServer() throws IOException{
    showMessage("Attempting connection ...");
    connection = new Socket(InetAddress.getByName(serverIP), 6789);
    showMessage("Connected to" +  connection.getInetAddress().getHostAddress());


}


//setup streams to send and receive messages;
private void setupStream() throws IOException{

    output = new ObjectOutputStream(connection.getOutputStream());
    input = new ObjectInputStream(connection.getInputStream());

}

private void receiveMessage() throws IOException{
    ableToType(true);
    while(true) {
        try {
            message = (String)input.readObject();
            showMessage("\n" + message);


        } catch (ClassNotFoundException classNotFoundException) {
            showMessage("\n Idk wtf dude!!");
            // TODO: handle exception
        }
    } 
}


private void sendMessage(String message){
    try {
        output.writeObject(": " + message);
        output.flush();
        showMessage("\nYou: " + message);
    } catch (IOException e) {
        chatWindow.append("\n Something went wrong");

        // TODO: handle exception
    }
}



//change / update chatWndows
private void showMessage(final String msg){
    SwingUtilities.invokeLater(
            new Runnable(){
                public void run(){
                    chatWindow.append(msg);
                }
            }
            );

}

private void ableToType(final boolean tof){
    SwingUtilities.invokeLater(
            new Runnable() {
                public void run(){
                    userText.setEditable(tof);
                }


            }
            );
}

@Override
public void run() {
    // TODO Auto-generated method stub

}



}

Answer 1

The for loop that removes the 'this' entry from the array should not be inside the read/write loop. The entry should only be removed when the client disconnects, ie. when an error/exception occurs. Check ALL your server and client code for such gross structural errors and use a debugger to trace code execution instead of continually editing corrections here