Java EE (Java Enterprise Edition) General Discussion

I got some error message in my programm Please help me .
Error Message is Written Below :

**MessagingException: Could not connect to SMTP host: localhost, port: 25; nested exception is: java.net.ConnectException: Connection refused: connect**

Programm is

import javax.servlet.*;

import javax.servlet.http.*;

import java.io.*;

import javax.mail.*;

import javax.mail.internet.*;   // important

import javax.mail.event.*;      // important

import java.net.*;

import java.util.*;

public class emailExa extends HttpServlet

{

    public  void service(HttpServletRequest request,HttpServletResponse response)

                                  throws ServletException, IOException

    {

        PrintWriter out=response.getWriter();

        response.setContentType("text/html");
//out.println("You are here");
        try

        {
//            ServerSocket s=new ServerSocket(8084);
//            Socket in=s.accept();
//            InputStream inStream=in.getInputStream();
//            OutputStream outStream=in.getOutputStream();
//            Scanner sn=new Scanner(inStream);
//            PrintWriter out1=new PrintWriter(outStream ,true);
           Properties props=new Properties();

           props.put("mail.smtp.host","localhost");   //  'localhost' for testing
             props.put("mail.smtp.port", "25");

         
           
   Session   session1  =  Session.getDefaultInstance(props,null);

           String s1 = request.getParameter("mailfrom"); //sender (from)

           String s2 = request.getParameter("mailto");

           String s3 = request.getParameter("mailsubject");

           String s4 = request.getParameter("mailcontent");

     Message message =new MimeMessage(session1);

      message.setFrom(new InternetAddress(s1));

      message.setRecipients

              (Message.RecipientType.TO,InternetAddress.parse(s2,false));

           message.setSubject(s3);

           message.setText(s4);        

           Transport.send(message);

//           out1.println("mail has been sent Successfull");
System.out.println("Successfull");
        }

        catch(Exception ex)

        {
out.println("mail has not been sent" + ex);
//           System.out.println("ERROR....."+ex);

        }

    }

}