06 Multithreaded TCP

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

public class Server {
    private ServerSocket server_socket;

    public Server(int port_no) throws IOException {
        server_socket = new ServerSocket(port_no);

        System.out.println("Waiting for client to connect");

        while (true) {
            try {
                Socket connection = server_socket.accept();
                System.out.println("Connected to client");

                ClientHandler client_handler = new ClientHandler(connection);
                client_handler.start();
            } catch (Exception e) {
        e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws IOException {
        new Server(5000);
    }
}

class ClientHandler extends Thread {

    public ClientHandler(Socket connection) throws IOException {
        try {
            DataOutputStream out = new DataOutputStream(connection.getOutputStream());
            String server_message = "Hi there! Enter something";
            out.writeUTF(server_message);

            DataInputStream in = new DataInputStream(connection.getInputStream());

            int num1 = Integer.parseInt(in.readUTF());
            String op = in.readUTF();
            int num2 = Integer.parseInt(in.readUTF());

            String client_reply = "Received: " + num1 + op + num2;
            System.out.println(client_reply);

            int result = 0;

            switch (op) {
                case "+": {
                    result = num1 + num2;
                    break;
                }
                case "-": {
                    result = num1 - num2;
                    break;
                }
                case "*": {
                    result = num1 * num2;
                    break;
                }
                case "/": {
                    result = num1 / num2;
                    break;
                }
                case "^": {
                    result = num1 ^ num2;
                    break;
                }
                default: {
                    System.out.println("Invalid Operator");
                }
            }

            out.writeUTF(Integer.toString(result));

            in.close();
            out.close();
            connection.close();

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

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

public class Client {
    public Client(String host, int port) throws IOException
  {
    try
    {
      Socket client = new Socket(host, port);

      System.out.println("Connected to server");

      DataInputStream in = new DataInputStream(client.getInputStream());

      String server_message = in.readUTF();
      System.out.println(server_message);

      DataOutputStream out = new DataOutputStream(client.getOutputStream());

      Scanner user_in = new Scanner(System.in);

      int num1 = user_in.nextInt();
      String op = user_in.next();
      int num2 = user_in.nextInt();

      out.writeUTF(Integer.toString(num1));
      out.writeUTF(op);
      out.writeUTF(Integer.toString(num2));


      String result = in.readUTF();
      System.out.println(result);

      user_in.close();
      client.close();
    } catch (Exception e)
    {
      e.printStackTrace();
    }
  }

    public static void main(String[] args) throws IOException {
        new Client("localhost", 5000);
    }
}