Java SMTP协议电子邮件传送

import java.io.*;
import java.net.NoRouteToHostException;
import java.net.Socket;
import java.util.*;
import javax.naming.NamingException;
import sun.misc.BASE64Encoder;
public class WorkThread extends Thread
{
    String domain;
    String to;
    String subject;
    String body;
    String myEncode="gb2312";
    public String  hosts[]={
       "google.com","sun.com","borland.com","dell.com","163.com","263.com",
       "sina.com","etang.com","sohu.com" };
    String from="ddd@"+getRandomDomain();
    public void run(){
       
        String mxServers[]=null;  
        MxFinder finder = new MxFinder(domain,"202.204.208.2");
        try
        {
            mxServers = finder.getMxServers();
        }
        catch(NamingException e)
        {
            e.printStackTrace();
        };
        if(mxServers==null)
        { 
            System.out.println("address is wrong");
        }else{  
           try{
              L1:
              for(int i=0;i<mxServers.length;i++)
              {    
                  String mxServer=mxServers[i];
                  for(int j=0;j<3;j++)
                  {   
                       Socket socket=new Socket(mxServer,25);
                       DataInputStream dis = new DataInputStream(socket.getInputStream());
                       DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
                       String response = "";
                       response = readLastLine(dis);
                       if(!response.startsWith("220"))  
                       {    
                           dis.close(); 
                           dos.close();
                           socket.close(); 
                           dis = null; 
                           dos = null; 
                           socket = null;                  
                           continue;         
                       } else {     //连接成功，开始写入HELO,标识自己身份
                           
                           dos.writeBytes("HELO "+domain+"\r\n");
                            response = readLastLine(dis);
                           if(!response.startsWith("250"))
                            {    //无法识别此域名，可在此进行相应处理；                                                           dis.close(); 
                                dos.close();
                                socket.close(); 
                                dis = null; 
                                dos = null; 
                                socket = null;                  
                                continue;   
                           } else 
                           {     //SMTP可以识别此域名；写入：MAIL FROM告诉服务器想发一封邮件；
                                                      
                               dos.writeBytes("MAIL FROM: "+from+"\r\n");
                               response = readLastLine(dis);
                               System.out.println(response);
                               if(!response.startsWith("250"))
                               {     //SMTP服务器不打算接收邮件，可在此做相应处理；   
                                  System.out.println("failure");                                                                    dis.close(); 
                                  dos.close();
                                  socket.close(); 
                                  dis = null; 
                                  dos = null; 
                                  socket = null;                  
                                  continue;    
                               } else 
                               {  //SMTP服务器准备接收邮件，写入RCPT TO告诉服务器收件人地址；
                                   
                                    dos.writeBytes("RCPT TO: <"+to+">\r\n");
                                    response = readLastLine(dis);
                                    if(!response.startsWith("250"))
                                    {     //SMTP不愿意为接收人接收邮件，可在此进行相应处理；                                              dis.close(); 
                                        dos.close();
                                        socket.close(); 
                                        dis = null; 
                                        dos = null; 
                                        socket = null;                  
                                        continue;        
                                     }else 
                                     { //SMTP愿意为接收入接收邮件，写入DATA表明开始邮件传送；
                                          
                                         dos.writeBytes("DATA\r\n");
                                         response = readLastLine(dis);
                                         if(!response.startsWith("354"))
                                         {      dis.close(); 
                                               dos.close();
                                               socket.close(); 
                                               dis = null; 
                                               dos = null; 
                                               socket = null;                  
                                                continue;          
                                         } else 
                                         {  //SMTP服务器同意开始输入邮件，对邮件体的//From,To,Subject,Data等做相应设置,写入要传送的邮件体//正文：body;
                                            
                                             dos.writeBytes("From:< "+getStr(from,myEncode)+">\r\n"); 
                                             dos.writeBytes("To: <"+getStr(to,myEncode)+">\r\n");    
                                             dos.writeBytes("Subject: "+getStr(subject,myEncode)+"\r\n");    
                                             dos.writeBytes("Reply-To: <"+from+">\r\n");  
                                                                                                 dos.writeBytes("mime-version: 1.0\r\n");
                                        
                                                         
                                             dos.writeBytes("Content-Type: text/html;\r\n");                                                                                                                 dos.writeBytes("Content-Transfer-Encoding: Base64");
                                       	  dos.writeBytes("\r\n\r\n");
                                             dos.writeBytes(getBase64(body));       
                                             dos.writeBytes("\r\n\r\n");                                                          dos.writeBytes("\r\n.\r\n");
                                             response =readLastLine(dis);
                                             if(!response.startsWith("250"))
                                             { //发送失败，可在此做相应处理；                                                                       dis.close(); 
                                                  dos.close();
                                                  socket.close(); 
                                                  dis = null; 
                                                  dos = null; 
                                                  socket = null;                  
                                                  continue;                                        
                                             } else
                                             {  //发送成功，结束此次传送；
                                               
                                                  dos.writeBytes("quit\r\n");
                                                  dis.close();
                                                  dos.close();
                                                  socket.close();
                                                  dis = null;
                                                  dos = null;
                                                  socket = null;                                                                                    break L1;
                                           }//sixth else
                                        }//fifth else
                                     }//fourth else
                                 }//third else
                             } //second else
                          }//first else
                      }
                   }
              }catch(Exception e){  e.printStackTrace();}
          }
      }//run end

     private String readLastLine(DataInputStream in) throws IOException
     {
        String ret = "";
        do
        {
            BufferedReader d= new BufferedReader(new InputStreamReader(in));
            ret=d.readLine();
        } while(in.available() > 0);
        return ret;
     }

    private String getBase64(String str)
    {
        return (new BASE64Encoder().encode(str.getBytes()));
    }  

     public static String getStr(String str, String encode)
    {
        try
        {
            byte temp[] = str.getBytes(encode);
            String tmp = new String(temp, "8859_1");
            String s = tmp;
            return s;
        }
        catch(Exception exception)
        {
            return null;
        }
    }

     private String getRandomDomain()
    {
        String ret = "";
        Random r = new Random(System.currentTimeMillis());
        ret = hosts[r.nextInt(hosts.length)];
        return ret;
    }

     public static void main(String[] args)
     {  
          WorkThread wt=new WorkThread();
          int pos;
          if(args.length<3) System.out.println("请输入您要发送到的邮件地址(如：[e-mail])、主题、内容");
             else{
                wt.to=args[0];
                wt.subject=args[1];
                wt.body=args[2];
                pos=wt.to.indexOf("@");
                if(pos==-1) System.out.println("您输入的地址错误，请重新输入");                 
                 else {   wt.domain=wt.to.substring(pos+1);
                          wt.start();
                      }
             }
     }
}