java聊天程序

mport java.util.*;
import java.net.*;
import java.io.*;

public class Server{
 public static final int port=10000;
 public static final Vector users=new Vector();
 public static void main(String args[]){
  ServerSocket server=null;
  try{
   server=new ServerSocket(port);
   System.out.println("Server start up on port :"+port);
   while(true){
    Socket s=server.accept();
    User user=new User(s);
    user.start();
   }
   

  }catch(Exception e){
   e.printStackTrace();
  }finally{

   if(server!=null&&!server.isClosed()){
    try{server.close();}catch(Exception e){}
   } 
  }
 }

}

class User extends Thread{
 private Socket s;
 private String userName;
 private InetAddress ip;
 public User(Socket s){
  this.s=s;
 }
 public void run(){
  try{
   InputStream input=s.getInputStream();
   OutputStream output=s.getOutputStream();
   BufferedReader buf=new
    BufferedReader(new
    InputStreamReader(input));
   PrintWriter pw=new
   PrintWriter(new OutputStreamWriter(output),true);
   
   pw.println("welcome u ,enter your name :");
   userName=buf.readLine();
   Server.users.add(this);
   sendAll(userName+" has join us ");;
   long t=0;
   while(true){
    String line=buf.readLine();
    long s=System.currentTimeMillis();
    if((s-t)/1000<3){
     pw.println("flush denied ");
     continue;
    }
    t=s;

 
    if(line==null||line.trim().length()==0){
    pw.println("flush denied ");
    continue;
    }
    if(line.equals("bye")){
     sendAll(userName+" leave us ");
     Server.users.remove(this); 
     break;
   
    }

    sendAll(userName+" said :"+line);
   }  
  }catch(Exception e){
   //e.printStackTrace();
  }finally{
   if(s!=null)try{s.close();}catch(Exception e){}
  }
 }
 public  synchronized void sendMessage(String message){
  try{
   PrintWriter pw=new
   PrintWriter(new OutputStreamWriter(
   s.getOutputStream()));
   pw.println(message);
   pw.flush();
  }catch(Exception e){}
 }
 public void sendAll(String message){
  Iterator it=Server.users.iterator();
  while(it.hasNext()){
   User user=(User)it.next();
   user.sendMessage(message);
  }
 }
}