// Sensor server
//
// Usage: SensorServer [port]
//
// Implements the generation of data samples for the example
// from section 1 of "Time-Recursive EM Examples", R. Perry, June 1998.

import java.io.*;
import java.util.Random;
import java.net.InetAddress;
import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.LocateRegistry;

public class SensorServer extends UnicastRemoteObject implements Sensor {   

  private Random Ran;
  private double p = 0.4;	/* P(1) */
  private double c = 2.0;	/* scale factor */
  private double s = 0.2;	/* noise standard deviation */

  public SensorServer() throws java.rmi.RemoteException
  {
    super();
    Ran = new Random();
  }
    
  public double get_y() throws RemoteException, ServerNotActiveException
  {
    System.out.println( "SensorServer: get_y() called from " + this.getClientHost());

    int b = (Ran.nextDouble() < p) ? 1 : 0;

    System.out.println( "b = " + b);

    double y = c*b + s*Ran.nextGaussian();

    System.out.println( "y = " + y);

    return y;
  }

  private static void createPortFile( int port) throws java.io.IOException
  {
    PrintWriter fout = new PrintWriter( new BufferedWriter( new FileWriter( "SensorServer.port")));
    fout.println( InetAddress.getLocalHost().getHostName());
    fout.println( port);
    if( fout.checkError()) {
      System.err.println( "SensorServer: error writing port file.");
      System.exit(1);
    }
    fout.close();
  }

  public static void main(String args[]) throws Exception
  {
    int port = 31099;

    if (args.length == 1)
      port = Integer.parseInt(args[0]);

    // Create and install the security manager
    //
    System.setSecurityManager(new RMISecurityManager());

    try {
      LocateRegistry.createRegistry(port);

      Sensor S = new SensorServer();
      Naming.rebind("rmi://:" + port + "/SensorServer", S);
 
      System.err.println("SensorServer: created and bound in the registry on port " + port);

    } catch (Exception e) {

      System.err.println("SensorServer: " + e);
      System.exit(1);
    }

    createPortFile( port);
  }
}