package udptest;import java.io.*;import java.net.*;/** * <p>Title: </p> * <p>Description: </p> * <p>Copyright: Copyright (c) 2003</p> * <p>Company: </p> * @author not attributable * @version 1.0 */public class UDPServerThread extends Thread {  private DatagramSocket UDPServerSocket = null;          public UDPServerThread(int port)          {                  try                  {                          UDPServerSocket=new DatagramSocket(port);                          System.out.println("郵件服務監聽在端口："+UDPServerSocket.getLocalPort()+"\n");                  }                  catch(Exception e)                  {                          System.err.println(e);                  }          }          public void run()          {                  if(UDPServerSocket == null)                          return;                  while(true)                  {                          try{                                  byte dataBuf[]=new byte[512];                                  DatagramPacket ServerPacket;                                  InetAddress RemoteHost;                                  int RemotePort;                                  String Datagram,s;                                  ServerPacket=new DatagramPacket(dataBuf,512);                                  UDPServerSocket.receive(ServerPacket);                                  RemoteHost=ServerPacket.getAddress();                                  RemotePort=ServerPacket.getPort();                                  Datagram=new String(ServerPacket.getData());                                  System.out.println("收到如下主機發來的郵件："                                      +RemoteHost.getHostName()                                          +":\n"+Datagram);                                  Datagram = new String(RemoteHost.getHostName()+                                          ":\n MailServer  "+InetAddress.getLocalHost().getHostName()                                          +" has already get your mails.");                                  for(int i=0;i<512;i++) dataBuf[i]=0;                                  Datagram.getBytes(0,Datagram.length(),dataBuf,0);                                  ServerPacket=new DatagramPacket(dataBuf,dataBuf.length,                                          RemoteHost,RemotePort);                                  UDPServerSocket.send(ServerPacket);                          }                          catch(Exception e)                          {                                  System.err.println(e);                          }                  }          }  protected void finalize()          {                  if(UDPServerSocket != null)                  {                          UDPServerSocket.close();                          UDPServerSocket=null;                          System.out.println("關閉服務器的數據報連接！");                  }          }}