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

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

  public Server()
  {
    System.out.println( "Server started at " + new Date() );

    try
    {
      // Create a server socket
      ServerSocket serverSocket = new ServerSocket( 8123 );

      // Listen for a connection request
      Socket socket = serverSocket.accept();

      // Create data input and output streams
      DataInputStream inputFromClient =
        new DataInputStream( socket.getInputStream() );
      DataOutputStream outputToClient =
        new DataOutputStream( socket.getOutputStream() );

      while ( true )
      {
        // Receive radius from the client
        double radius = inputFromClient.readDouble();

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

        // Send area back to the client
        outputToClient.writeDouble( area );

        System.out.println( "Radius received from client: " + radius );
        System.out.println( "Area found: " + area );
      }
    }
    catch( IOException ex )
    {
      System.err.println( ex );
    }
  }
}