import java.net.Socket;

import java.net.ServerSocket;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.File;

import java.io.FilenameFilter;

public class EchoServer{

public static final int ECHO_SERVER_PORT = 9999;

public static void main(String[] args){

System.out.println("EchoServer started.");

ServerSocket ss = null;

try{

ss = new ServerSocket(ECHO_SERVER_PORT);

}catch(IOException ioe){

ioe.printStackTrace();

return;

}

File indicatingFile = new File("kill"); // Just represents file path.

do{

try{

Socket socket = ss.accept();

// explore the ports.

System.out.println("LocalPort: " + socket.getLocalPort() + ", RemotePort: " + socket.getPort());

InputStream is = socket.getInputStream();

BufferedReader br = new BufferedReader(new InputStreamReader(is));

String incomingMsg = br.readLine();

System.out.println("ReceiveMsg: " + incomingMsg);

OutputStream os = socket.getOutputStream();

PrintWriter pw = new PrintWriter(os);

pw.println(incomingMsg);

pw.flush();

socket.close();

}catch(IOException ioe){

ioe.printStackTrace();

}

}while(!commandKill(indicatingFile));

if(ss!=null){

try{

ss.close();

}catch(IOException ioe){

ioe.printStackTrace();

}

}

}

static boolean commandKill(File file){

return file.exists() && file.isFile();

// Just need to verify the existence of the single interesting file, not need to use filter.

}

}