public class Server {

    public static void main(String[] args) {
        int port = genPort(args);

        ServerSocket server = null;
        ExecutorService service = Executors.newFixedThreadPool(50);

        try{
            server = new ServerSocket(port);
            System.out.println("server started!");
            while(true){
                Socket socket = server.accept();

                service.execute(new Handler(socket));
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            if(server != null){
                try {
                    server.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            server = null;
        }
    }

    static class Handler implements Runnable{
        Socket socket = null;
        public Handler(Socket socket){
            this.socket = socket;
        }
        @Override
        public void run() {
            BufferedReader reader = null;
            PrintWriter writer = null;
            try{

                reader = new BufferedReader(
                        new InputStreamReader(socket.getInputStream(), "UTF-8"));
                writer = new PrintWriter(
                        new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));
                String readMessage = null;
                while(true){
                    System.out.println("server reading... ");
                    if((readMessage = reader.readLine()) == null){
                        break;
                    }
                    System.out.println(readMessage);
                    writer.println("server recive : " + readMessage);
                    writer.flush();
                }
            }catch(Exception e){
                e.printStackTrace();
            }finally{
                if(socket != null){
                    try {
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                socket = null;
                if(reader != null){
                    try {
                        reader.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                reader = null;
                if(writer != null){
                    writer.close();
                }
                writer = null;
            }
        }

    }

    private static int genPort(String[] args){
        if(args.length > 0){
            try{
                return Integer.parseInt(args[0]);
            }catch(NumberFormatException e){
                return 9999;
            }
        }else{
            return 9999;
        }
    }

}

public class Client {
    public static void main(String[] args) {
        String host = null;
        int port = 0;
        if(args.length > 2){
            host = args[0];
            port = Integer.parseInt(args[1]);
        }else{
            host = "127.0.0.1";
            port = 9999;
        }

        Socket socket = null;
        BufferedReader reader = null;
        PrintWriter writer = null;
        Scanner s = new Scanner(System.in);
        try{
            socket = new Socket(host, port);
            String message = null;

            reader = new BufferedReader(
                    new InputStreamReader(socket.getInputStream(), "UTF-8"));
            writer = new PrintWriter(
                    socket.getOutputStream(), true);
            while(true){
                message = s.nextLine();
                if(message.equals("exit")){
                    break;
                }
                writer.println(message);
                writer.flush();
                System.out.println(reader.readLine());
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            socket = null;
            if(reader != null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            reader = null;
            if(writer != null){
                writer.close();
            }
            writer = null;
        }
    }
}