inetexample.java

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/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

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

public class InetExample {
  public static void main (String args[]) {
    printLocalAddress ();
    Reader kbd = new FileReader (FileDescriptor.in);
    BufferedReader bufferedKbd = new BufferedReader (kbd);
    try {
      String name;
      do {
        System.out.print ("Enter a hostname or IP address: ");
        System.out.flush ();
        name = bufferedKbd.readLine ();
        if (name != null)
          printRemoteAddress (name);
      } while (name != null);
      System.out.println ("exit");
    } catch (IOException ex) {
      System.out.println ("Input error:");
      ex.printStackTrace ();
    }
  }

  static void printLocalAddress () {
    try {
      InetAddress myself = InetAddress.getLocalHost ();
      System.out.println ("My name : " + myself.getHostName ());
      System.out.println ("My IP : " + myself.getHostAddress ());
      System.out.println ("My class : " + ipClass (myself.getAddress ()));
    } catch (UnknownHostException ex) {
      System.out.println ("Failed to find myself:");
      ex.printStackTrace ();
    }
  }

  static char ipClass (byte[] ip) {
    int highByte = 0xff & ip[0];
    return (highByte < 128) ? 'A' : (highByte < 192) ? 'B' :
      (highByte < 224) ? 'C' : (highByte < 240) ? 'D' : 'E';
  }

  static void printRemoteAddress (String name) {
    try {
      System.out.println ("Looking up " + name + "...");
      InetAddress machine = InetAddress.getByName (name);
      System.out.println ("Host name : " + machine.getHostName ());
      System.out.println ("Host IP : " + machine.getHostAddress ());
      System.out.println ("Host class : " +
                          ipClass (machine.getAddress ()));
    } catch (UnknownHostException ex) {
      System.out.println ("Failed to lookup " + name);
    }
  } 
}