I use below code to establish socket and write back string to out1 stream to client .

I accept the socket socket and out1 stream in run() , I use another function p_output_socket() to write back the string to out1 stream , but I find there is nul exception . probably, it is indicate that the server socket variable is null in function
p_output_socket() . It is ok in run function .
Pleae advice how I can pass the current server socket variable to function p_output_socket and use it ???
Below is the code

import java.io.File;
 import java.io.FileInputStream;
 import java.io.*;

import java.util.ArrayList;
import java.util.List;

import java.net.*;

import org.apache.commons.httpclient.HttpClient;
 import org.apache.commons.httpclient.methods.InputStreamRequestEntity;
 import org.apache.commons.httpclient.methods.PostMethod;
 import org.apache.commons.httpclient.methods.DeleteMethod;
import org.apache.commons.httpclient.methods.PutMethod;
import org.apache.commons.httpclient.methods.*;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.*;
import java.lang.Thread.*;
/* below use for http get */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import org.apache.http.*;

import java.io.*;
import java.nio.channels.*;
import java.util. * ;
import java.io. * ;
import java.io.RandomAccessFile.*;
import java.io.RandomAccessFile;


import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.*;
import java.net.URL;
import java.net.URI;
import java.io.*;


import java.sql.*;
import javax.sql.*;
import com.mysql.jdbc.Driver;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;


public class doComms implements Runnable   {
    public static Socket server;
    public static ServerSocket listener;
    Thread t;

public static Statement stmt ;



    public String line,input,testabc;
   // public  DataOutputStream out1 ;
    public DataInputStream in;
    public static PrintWriter out1;
   doComms() {
 //Socket server;
  //   ServerSocket listener;
 //PrintWriter out1;

     //t = new Thread (this,"socket server 4444 run ");

     // t.start(); // Start the thread
  try {
listener = new ServerSocket(4444);

       }
     catch ( Exception y )  { y.printStackTrace();  }

    }

    public void run () {



    testabc="123";
      input="";

      try {


      Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection ("jdbc:mysql://10.1.1.89:3306/mysql", "root", "123456");
Statement stmt = con.createStatement();

       //listener = new ServerSocket(4444);
      //Socket server;


        doComms connection;

          server = listener.accept();


          // Get input from the client
          System.out.println("Start up socket input stream !!!");

          in = new DataInputStream (server.getInputStream());

          System.out.println("Start up socket output stream !!!");
          //out1 = new PrintStream(server.getOutputStream());

          PrintWriter out1 = new PrintWriter(
                             new BufferedOutputStream(server.getOutputStream(), 1024), false);

          //out1 = new DataOutputStream(server.getOutputStream());

      ClientHandler abc = new ClientHandler(server);

      Thread socserver = new Thread(abc);

           socserver.start();

        while((line = in.readLine()) != null && !line.equals(".")) {
          input=input + line;
          if ( line.startsWith("abc") )
           {
            System.out.println("put ok in out socket in docomms");
            out1.println("OK" );
          out1.flush();
        p_output_socket("testing ok");
            }
          else
          {
          System.out.println("put echo  in out socket in docomms");
            out1.println("echo what I get only :" + line);
          out1.flush();
        p_output_socket("testing echo ok");
            }




       









        }

        // Now write to the client

        System.out.println("Overall message is:" + input);
        p_output_socket("Overall message is:" + input);

        server.close();
      } catch (Exception e) {
        System.out.println("Exception on socket listen: " + e);
        e.printStackTrace();
      }
    }
   //below print string to output socket
   public  void p_output_socket(String a )
   {

     String input1 = this.input;
     String line1 = this.line ;


     try
     {
     //System.out.println("this testabc " + this.testabc );
     //System.out.println("this input " + this.input );
     //System.out.println("this line " + this.line );
     //System.out.println("a is " + a );



        String aa =a ;

          out1.println( aa );
          out1.flush();



       }
      catch ( Exception e) {
        System.out.println("Exception on socket output in DoComms " + e);
        e.printStackTrace();
      }



    }

   // above print string to output socket

 public static void insert_order_sql (Statement stmt,String v)
  {
    try {
    stmt.executeUpdate("INSERT INTO `o1` (`data` ) " + "VALUES ( '"+v+"' )");
        }
   catch ( Exception w )  { w.printStackTrace();      }

   }



}