ServerGui.java

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.text.DefaultCaret;


public class ServerGui extends JFrame{

    //Initialize components
    JPanel mainPanel = null;

    JTextArea chtArea = null;
    JScrollPane chtScroll = null;
    DefaultCaret chtScrCaret = null;

    JPanel subPanel = null;

    JTextField txtMessage = null;
    JButton btnSnd = null;
    JButton btnCls = null;
    Server s = null;

    public ServerGui() {
        super("ServerChat");


        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

        //Create components and set properties
        mainPanel = (JPanel)getContentPane();
        mainPanel.setLayout(new BorderLayout());

        chtArea = new JTextArea();
        chtScroll = new JScrollPane(chtArea);
        chtScrCaret = (DefaultCaret)chtArea.getCaret();
        chtScrCaret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);

        subPanel = new JPanel();
        subPanel.setLayout(new FlowLayout());

        txtMessage = new JTextField("");
        txtMessage.setPreferredSize(new Dimension(300,20));

        btnSnd = new JButton("Send");
        btnCls = new JButton("Close");

        btnSnd.addActionListener(new SendActionListener());
        btnCls.addActionListener(new CloseActionListener());
        btnSnd.setEnabled(false); // default false

        subPanel.add(txtMessage);
        subPanel.add(btnSnd);
        subPanel.add(btnCls);
        mainPanel.add(chtScroll, BorderLayout.CENTER);
        mainPanel.add(subPanel, BorderLayout.SOUTH);

        setSize(480,400);
        setResizable(false);


        //Creates the server
        s = new Server();

        //Keep reading the socket
        while(true) {
            chtArea.append("\nClient: "+s.readSocket()+"\n");

        }
    }

    // Buttons ActionListeners class
    public class SendActionListener implements ActionListener{
        //For button send
        @Override
        public void actionPerformed(ActionEvent e) {
            s.writeSocket(txtMessage.getText());
            chtArea.append("\nYou: "+txtMessage.getText()+"\n");
            txtMessage.setText("");
        }

    }

    public class CloseActionListener implements ActionListener{
        //For button close
        @Override
        public void actionPerformed(ActionEvent e) {
            System.exit(DISPOSE_ON_CLOSE);
            s.closeConnection();
        }

    }


    // Server class

    public class Server {

        // Initialize sockets and socket streams
        ServerSocket ss = null;
        Socket soc = null;
        DataInputStream sdis = null;
        DataOutputStream sdos = null;
        int port = 3333;
        boolean notConnected;

        //Create connection when Server is created
        public Server() {
            createConnection();
        }

        public void createConnection() {
            notConnected = true; //default false

            while(notConnected) {

                //Create server connection
                try {
                    chtArea.append("Creating server... \n");
                    ss = new ServerSocket(port);
                    soc = ss.accept();
                    Thread.sleep(2000);
                    notConnected = false;
                    chtArea.setText("");
                    chtArea.append("Server Established! \n");
                    btnSnd.setEnabled(true);


                } catch (Exception e) {

                    //When failed disable send button.
                    chtArea.append("Error on Connection. \n");
                    btnSnd.setEnabled(false);

                    try {
                        chtArea.append("Trying to reconnect... \n");
                        Thread.sleep(2000);
                    } catch (InterruptedException e1) {
                        chtArea.append("Error reconnecting. \n");
                        e1.printStackTrace();
                    }

                }

            }

            //Creates the socket streams
            try {
                sdis = new DataInputStream(soc.getInputStream());
                sdos = new DataOutputStream(soc.getOutputStream());

            } catch (Exception e) {
                chtArea.append("Error on creating streams. \n");
            }

        }

        //for reading data on socket streams
        public String readSocket() {
            try {
                return sdis.readUTF();
            } catch (Exception e) {
                // try to reconnect when read fails
                s = new Server();

                if(notConnected) {
                    return "Error on read or connection timeout \n";
                }else {
                    return "Reconnection success";
                }
            }
        }

        //for writing data on socket streams
        public String writeSocket(String ms) {
            try {
                sdos.writeUTF(ms);
                return ms;
            } catch (Exception e) {
                return "Error on write or connection timeout\n";
            }

        }

        //for closing socket connections
        public void closeConnection(){

            try {
                ss.close();
                soc.close();
                sdis.close();
                sdos.close();

            } catch (Exception e) {
                chtArea.append("Error closing connection. \n");
            }
        }

    }



}