// MultiThreadsServer.java: The server can communicate with
// multiple clients concurrently using the multiple threads
package Chapter16;

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

public class MultiThreadsServer
{
  // Main method
  public static void main(String[] args)
  {
    try
    {
      // Create a server socket
      ServerSocket serverSocket = new ServerSocket(8000);

      // Number a thread
      int i = 0;

      while (true)
      {
        // Listen for a new connection request
        Socket connectToClient = serverSocket.accept();

        // Print the new connect number on the console
        System.out.println("Starting thread "+i);

        // Create a new thread for the connection
        ThreadHandler thread = new ThreadHandler(connectToClient, i);

        // Start the new thread
        thread.start();

        // Increment i to number the next connection
        i++;
      }
    }
    catch(IOException ex)
    {
      System.err.println(ex);
    }
  }
}

// Define the thread class for handling a new connection
class ThreadHandler extends Thread
{
  private Socket connectToClient; // A connected socket
  private int counter; // Number the thread

  // Construct a thread
  public ThreadHandler(Socket socket, int i)
  {
    connectToClient = socket;
    counter = i;
  }

  // Implement the run() method for the thread
  public void run()
  {
    try
    {
      // Create data input and print streams
      BufferedReader isFromClient = new BufferedReader(
        new InputStreamReader(connectToClient.getInputStream()));
      PrintWriter osToClient =
        new PrintWriter(connectToClient.getOutputStream(), true);

      // Continuously serve the client
      while (true)
      {
        // Receive data from the client in string
        StringTokenizer st = new StringTokenizer
          (isFromClient.readLine());

        // Get radius
        double radius = new Double(st.nextToken()).doubleValue();
        System.out.println("radius received from client: "+radius);

        // Compute area
        double area = radius*radius*Math.PI;

        // Send area back to the client
        osToClient.println(area);
        System.out.println("Area found: "+area);
      }
    }
    catch(IOException ex)
    {
      System.err.println(ex);
    }
  }
}