Handling multiple clients

Question

I am trying to create a server that accepts multiple connections. I know that this question is asked a lot, but I cannot figure out what is wrong with mine...aside, possibly, everything. This is my server code, I used a frame to display this information and the code is pretty rough because I am brand new to this networking stuff (I am finding it pretty difficult).
import java.awt.*;
import java.util.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.event.*;
public class ServerFrame extends JFrame {
     private JTextField enterField;
     private JTextArea displayArea;
     private ObjectOutputStream output;
     private ObjectInputStream input;
     private ServerSocket server;
     private Socket connection;
     private int counter = 1;
     private String name;
     public ServerFrame() {
        super("Server");
        name = JOptionPane.showInputDialog("Enter your name: ","Mark");
        enterField = new JTextField();
        enterField.setEditable(false);
        enterField.addActionListener(
             new ActionListener(){
                  public void actionPerformed(ActionEvent event){
                       sendData(event.getActionCommand());
                       enterField.setText("");
        add(enterField, BorderLayout.NORTH);
        displayArea = new JTextArea();
        add(new JScrollPane(displayArea), BorderLayout.CENTER);
        setSize(400,250);
        setVisible(true);
    public void runServer(){
         try{
              server = new ServerSocket(12345,100);
              while(true){
                   try{
                        waitForConnection();
                        getStreams();
                        processConnection();
                   catch(EOFException eofException){
                        displayMessage("\nServer terminated connection");
                   finally{
                        closeConnection();
                        counter++;
                        continue;
         catch(IOException ioException){
              ioException.printStackTrace();
    private void waitForConnection() throws IOException{
         displayMessage("Waiting for connection\n");
         connection = server.accept();
         ServerClass Client = new ServerClass(connection);
         Client.start();
         displayMessage("Connection " + counter + " received from: " +
         connection.getInetAddress().getHostName() + " (IP: " +connection.getInetAddress().getHostAddress() +")");
    private void getStreams() throws IOException{
         output = new ObjectOutputStream(connection.getOutputStream());
         output.flush();
         input = new ObjectInputStream(connection.getInputStream());
         displayMessage("\n--Accpeted User--\n");
    private void processConnection() throws IOException{
         String message = "";
         sendData(message);
         setTextFieldEditable(true);
         do{
              try{
                   message = (String) input.readObject();
                   displayMessage("\n" + message);
              catch(ClassNotFoundException classNotFoundException){
                   displayMessage("\nUnknown object type received");
         } while(!message.equals("CLIENT>>> TERMINATE"));
    private void closeConnection(){
         displayMessage("\nTerminating connection\n");
         setTextFieldEditable(false);
         try{
              output.close();
              input.close();
              connection.close();
         catch(IOException ioException){
              ioException.printStackTrace();
    private void sendData(String message){
         try{
              output.writeObject(name+": " +message);
              output.flush();
              displayMessage("\n"+name+": " + message);
         catch(IOException ioException){
              displayArea.append("\nError writing object");
    private void displayMessage(final String messageToDisplay){
         SwingUtilities.invokeLater(
              new Runnable(){
                   public void run(){
                   displayArea.append(messageToDisplay);
    private void setTextFieldEditable(final boolean editable){
         SwingUtilities.invokeLater(
              new Runnable(){
                   public void run(){
                        enterField.setEditable(editable);
    protected void windowClosed() {
        System.exit(0);
}I used an example from our class books, but I have modified it a bit. The waitForConnections() method is where the server listens for incoming clients. The ServerClass constructor is as follows:
import java.net.*;
import java.util.*;
import javax.swing.*;
import java.io.*;
public class ServerClass extends Thread
     Socket SOCK = null;
     public ServerClass(Socket sock)
          SOCK = sock;
     public void run(){
          try{
               PrintWriter out = new PrintWriter(SOCK.getOutputStream(),true);
               BufferedReader in = new BufferedReader(
                    new InputStreamReader(
                         SOCK.getInputStream()));
          out.close();
          in.close();
          SOCK.close();
     }catch(IOException e){
          e.printStackTrace();
}I used the ServerClass to try and make a thread that would construct itself each time a new connection is made to the server. I honestly cannot say where I went wrong or where I am looking for the problems... I am not very familiar with threads either, but I have been trying.
If somebody could help me out here, I would really appreciate it, thank you.

Answer 1

Well, I believe the biggest problem is somewhere in my thread. I have tried using this thread to create sockets and allow connections, but whenever I try to host the server, it won't even accept connections. It accepts then terminates. Before I start to talk about the actual connection process, I need verification on this thread I made to see if it would work. Again, I am not exactly sure what the PrintWriter and BufferedReader do...I followed some examples and have been experimenting with them. I have looked it over several times and I think it looks right, but I am very new to this network programming and whatnot so I am not certain of how close I am.
import java.net.*;
import java.util.*;
import javax.swing.*;
import java.io.*;
public class ServerClass extends Thread
     Socket SOCK = null;
     public ServerClass(Socket sock)
          SOCK = sock; //hopefully this will take the server.accept() method.
     public void run(){
          try{
                  PrintWriter out = new PrintWriter(SOCK.getOutputStream(),true);
               BufferedReader in = new BufferedReader(
                    new InputStreamReader(
                         SOCK.getInputStream()));
          out.close();
          in.close();
          SOCK.close();
     }catch(IOException e){
          e.printStackTrace();
}