Error when using Socket class in swing

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Java

Swing

sockets

I am try to build a client server chat application using swing.In that when i start client i send a message that i can received at client site but when i press a button on Server site it will not open up a new Frame (that is in my case error here).How can i solve it...
And can any one suggest me some other way..
My code is(server site):

import java.net.*;
   import java.io.*;
   import javax.swing.*;
   import java.awt.event.*;
   import java.awt.*;
   import java.sql.*;
   class Cli extends JFrame
   {
      ServerSocket ss;
      Socket soc;
      InputStream in;
      OutputStream out;

      DataInputStream sin;
      DataOutputStream sout;

      JLabel l1;
      JTextField txt1;
      JButton addd;
     Cli()  throws Exception
     {
   Class.forName("com.mysql.jdbc.Driver");
   Connection cn=DriverManager.getConnection("jdbc:mysql://localhost:3306/nirav","root","root");
   JPanel pan=new JPanel(new GridLayout(2,1));
   ss=new ServerSocket(8888);
   //ss.setSOLimit(10000);
   l1=new JLabel("waiting for client");
   txt1=new JTextField(40);
   addd=new JButton("click here to send");
   addd.addActionListener(new ActionListener()
         {
       public void actionPerformed(ActionEvent ae)
           {   try{
                   JOptionPane.showMessageDialog(null,"Data is successfully inserted into the database." );
                   l1.setText("waiting");
                   Recieve c=new Recieve();
                   c.setSize(300,300);
                   c.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
                   c.setVisible(true);

                   }catch(Exception e)
                   {
                   System.out.println(e.toString());
                   }
               }
           });
   soc=ss.accept();
   in=soc.getInputStream();
   out=soc.getOutputStream();
   sin=new DataInputStream(in);
   sout=new DataOutputStream(out);
   String s="";
   try{
       s=sin.readUTF();
       }catch(Exception e)
       {
       }
       l1.setText("client :"+s);
   pan.add(l1);
   pan.add(txt1);
   pan.add(addd);
   add(pan);
   }
   class Recieve extends JFrame
   {
   JLabel msg;
   JTextField t1;
   JButton a1;
    Recieve() throws Exception
    {
   JPanel pan=new JPanel(new GridLayout(2,1));
   t1=new JTextField(40);
   a1=new JButton("click here to send");
   //msg=new JLabel("waiting...");
    a1.addActionListener(new ActionListener()
   {   public void actionPerformed(ActionEvent ae)
           {   try{
                   String s;
                   String str="Server :";
                   sout.writeUTF(t1.getText());
                   //msg.setText(str);
                   sout.flush();
               }catch(Exception e)
   {
   System.out.println(e.toString());
   }
   }});
   pan.add(t1);
   pan.add(a1);
   add(pan);
      }
      }
     }
    class Server
   {
     public static void main(String args[]) throws Exception
   {
   try{

   Cli c=new Cli();
   c.setSize(300,300);
   c.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   c.setVisible(true);
   }
   catch(Exception e)
   {
   System.out.println(e.toString());
   }

   }
     }