Multi client server Java program

I code a multi client server java program to simulate a multiuser game program. Each client will take turn to input. If a client input "OK", all the clients will end normally except itself. I need to press Enter on this client in order to end it probably.

How can I modify the code such that this client (input "OK") will also end itself normally.

Thx 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;


public class Server {
public static void main(String args[]){

   int PlayerIdx = 0;

    Socket s=null;
    ServerSocket ss2=null;
    System.out.println("Server Listening......");
    try{
        ss2 = new ServerSocket(4445); // can also use static final PORT_NUM , when defined

    }
   catch(IOException e){
    e.printStackTrace();
    System.out.println("Server error");

    }

   GameWinner game = new GameWinner(false);
   
    while(true){
      try{
            s= ss2.accept();
            System.out.println("connection Established");
            ServerThread st=new ServerThread(s, PlayerIdx, game);  //start new thread for any incoming connection
            PlayerIdx++;
            st.start();

      }
      catch(Exception e){
            e.printStackTrace();
            System.out.println("Connection Error");

      }
    }

}

}

class GameWinner {
   boolean gameover;
   
   GameWinner(boolean bover)
   {
      this.gameover = bover;
   }
    
   boolean GetWinner(){
      return gameover;
   }
   
   void SetWinner(boolean bover){
      this.gameover = bover;
   }
}

class ServerThread extends Thread{  

    String line=null;
    BufferedReader  is = null;
    PrintWriter os=null;
    Socket s=null;
   
   int PlayerID;
   boolean neverPlay= true;
   GameWinner GamePlay;


    public ServerThread(Socket s, int p, GameWinner g){
        this.s=s;
      this.PlayerID=p;
      this.GamePlay=g;

    }

  public void run() {
    try{
        is= new BufferedReader(new InputStreamReader(s.getInputStream()));
        os=new PrintWriter(s.getOutputStream());

    }catch(IOException e){
        System.out.println("IO error in server thread");
    }
   try {
      
        line = "";
      
      while (line.compareTo("QUIT")!=0)  {
         
         //Sync Start
         synchronized(GamePlay) {
            if (neverPlay == false) {
               try {            
                  GamePlay.wait();  //wait for execution
                                    
               }catch(InterruptedException e){
                  e.printStackTrace();
               }
            }
            
            
            if (!GamePlay.GetWinner()) {
               try{
                  os.println(PlayerID + ", your turn now" );  // send message to client
                  os.flush();  //forces any buffered output bytes to be written out to their intended destination
            
                  line=is.readLine();         
                  System.out.println("Client Input :  " + line);

                  System.out.println("Game Start");
                  Thread.currentThread().sleep(5000);
                  System.out.println("Game End");
                }
               catch (InterruptedException itro){
                   System.out.println("sleep is interrupted");
               }   
            }
            
            if (line.compareTo("OK")==0) {
               line = "";
               GamePlay.SetWinner(true);
               System.out.println("Player " + PlayerID + "win the Game");
               os.println(PlayerID + ", you win the game." );  // send message to client
               os.flush();  //forces any buffered output bytes to be written out to their intended destination
            }else if (GamePlay.GetWinner()) {
               os.println("QUIT");   //send to the server
               os.flush();
            } 
            neverPlay=false;
            GamePlay.notify();  //notify execution
   
         }  //Sync End
               
        }   
    } catch (IOException e) {

        line=this.getName(); //reused String line for getting thread name
        System.out.println("IO Error/ Client "+line+" terminated abruptly");
    }
    catch(NullPointerException e){
        line=this.getName(); //reused String line for getting thread name
        System.out.println("Client "+line+" Closed");
    }
finally{    
    try{
        System.out.println("Connection Closing..");
        if (is!=null){
            is.close(); 
            System.out.println(" Socket Input Stream Closed");
        }

        if(os!=null){
            os.close();
            System.out.println("Socket Out Closed");
        }
        if (s!=null){
        s.close();
        System.out.println("Socket Closed");
        }
    }
    catch(IOException ie){
        System.out.println("Socket Close Error");
    }
    }//end finally
    }
}

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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;

public class Client {

public static void main(String args[]) throws IOException{


    InetAddress address=InetAddress.getLocalHost();
    Socket s1=null;
   BufferedReader is=null;
   
    String line=null;
    BufferedReader br=null;
    
    PrintWriter os=null;   
   
   try {
        s1=new Socket(address, 4445);  
        
      //get server response, read from BufferedReader, console input
      br= new BufferedReader(new InputStreamReader(System.in));
      
      //get socket's input stream and open BufferedReader
        is=new BufferedReader(new InputStreamReader(s1.getInputStream()));
        
      //get sockets output stream and opens a PrinterWriter
      //(send data through socket to server and write to PrinterWriter
      os= new PrintWriter(s1.getOutputStream()); 
    }
    catch (IOException e){
        e.printStackTrace();
        System.err.print("IO Exception");
    }
   System.out.println("Client Address : "+address);
    System.out.println("Enter Data to echo Server ( Enter QUIT to end):");

    String response=null;
    try{
         line = "";
        while(line.compareTo("QUIT")!=0){
         
         response=is.readLine();   //read a line of information from BufferedReader connected to the socket
            System.out.println("Server Response : "+response);
         
         if (response.compareTo("QUIT")!=0) {
            line=br.readLine();
            os.println(line);   //send to the server
            os.flush();
         } else {
            line = "QUIT";
            os.println("QUIT");   //send to the server
            os.flush();
         }
        }
    }
    catch(IOException e){
        e.printStackTrace();
    System.out.println("Socket read Error");
    }
    finally{

        br.close();os.close();br.close();s1.close();
                System.out.println("Connection Closed");

    }

}
}

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