inetaddress.java

This is a resource based on j2me embedded,if you dont understand,you can connection with me .

/*
 * @(#)InetAddress.java	1.89 06/10/10 
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.net;

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Random;
import java.util.Iterator;
import java.util.LinkedList;
import java.security.AccessController;
import java.io.ObjectStreamException;
import sun.security.action.*;
import sun.net.InetAddressCachePolicy;
import sun.misc.Service;
import sun.net.spi.nameservice.*;

/**
 * This class represents an Internet Protocol (IP) address.
 *
 * <p> An IP address is either a 32-bit or 128-bit unsigned number
 * used by IP, a lower-level protocol on which protocols like UDP and
 * TCP are built. The IP address architecture is defined by <a
 * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
 * Assigned Numbers</i></a>, <a
 * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
 * Address Allocation for Private Internets</i></a>, <a
 * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
 * Administratively Scoped IP Multicast</i></a>, and <a
 * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
 * Version 6 Addressing Architecture</i></a>. An instance of an
 * InetAddress consists of an IP address and possibly its
 * corresponding host name (depending on whether it is constructed
 * with a host name or whether it has already done reverse host name
 * resolution).
 *
 * <h4> Address types </h4>
 *
 * <blockquote><table cellspacing=2 summary="Description of unicast and multicast address types">
 *   <tr><th valign=top><i>unicast</i></th>
 *       <td>An identifier for a single interface. A packet sent to
 *         a unicast address is delivered to the interface identified by
 *         that address.
 *
 *         <p> The Unspecified Address -- Also called anylocal or wildcard 
 *         address. It must never be assigned to any node. It indicates the
 *         absence of an address. One example of its use is as the target of
 *         bind, which allows a server to accept a client connection on any
 *         interface, in case the server host has multiple interfaces.
 *
 *         <p> The <i>unspecified</i> address must not be used as
 *         the destination address of an IP packet.
 *        
 *         <p> The <i>Loopback</i> Addresses -- This is the address
 *         assigned to the loopback interface. Anything sent to this
 *         IP address loops around and becomes IP input on the local
 *         host. This address is often used when testing a
 *         client.</td></tr>
 *   <tr><th valign=top><i>multicast</i></th>
 *       <td>An identifier for a set of interfaces (typically belonging 
 *         to different nodes). A packet sent to a multicast address is
 *         delivered to all interfaces identified by that address.</td></tr>
 * </table></blockquote>
 *
 * <h4> IP address scope </h4>
 *
 * <p> <i>Link-local</i> addresses are designed to be used for addressing
 * on a single link for purposes such as auto-address configuration,
 * neighbor discovery, or when no routers are present. 
 *
 * <p> <i>Site-local</i> addresses are designed to be used for addressing
 * inside of a site without the need for a global prefix.
 *
 * <p> <i>Global</i> addresses are unique across the internet.
 *
 * <h4> Textual representation of IP addresses </h4>
 * 
 * The textual representation of an IP address is address family specific.
 *
 * <p>
 *
 * For IPv4 address format, please refer to <A
 * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 * address format, please refer to <A
 * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 *
 * <h4> Host Name Resolution </h4>
 * 
 * Host name-to-IP address <i>resolution</i> is accomplished through
 * the use of a combination of local machine configuration information
 * and network naming services such as the Domain Name System (DNS)
 * and Network Information Service(NIS). The particular naming
 * services(s) being used is by default the local machine configured
 * one. For any host name, its corresponding IP address is returned.
 *
 * <p> <i>Reverse name resolution</i> means that for any IP address,
 * the host associated with the IP address is returned.
 *
 * <p> The InetAddress class provides methods to resolve host names to
 * their IP addresses and vise versa.
 *
 * <h4> InetAddress Caching </h4>
 *
 * The InetAddress class has a cache to store successful as well as
 * unsuccessful host name resolutions. The positive caching is there
 * to guard against DNS spoofing attacks; while the negative caching
 * is used to improve performance.
 *
 * <p> By default, the result of positive host name resolutions are
 * cached forever, because there is no general rule to decide when it
 * is safe to remove cache entries. The result of unsuccessful host
 * name resolution is cached for a very short period of time (10
 * seconds) to improve performance.
 *
 * <p> Under certain circumstances where it can be determined that DNS
 * spoofing attacks are not possible, a Java security property can be
 * set to a different Time-to-live (TTL) value for positive
 * caching. Likewise, a system admin can configure a different
 * negative caching TTL value when needed.
 *
 * <p> Two Java security properties control the TTL values used for
 *  positive and negative host name resolution caching:
 * 
 * <blockquote>
 * <dl>
 * <dt><b>networkaddress.cache.ttl</b> (default: -1)</dt>
 * <dd>Indicates the caching policy for successful name lookups from
 * the name service. The value is specified as as integer to indicate
 * the number of seconds to cache the successful lookup.
 * <p>
 * A value of -1 indicates "cache forever".
 * </dt><p>
 * <p>
 * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 * <dd>Indicates the caching policy for un-successful name lookups
 * from the name service. The value is specified as as integer to
 * indicate the number of seconds to cache the failure for
 * un-successful lookups.
 * <p>
 * A value of 0 indicates "never cache".
 * A value of -1 indicates "cache forever".
 * </dd>
 * </dl>
 * </blockquote>
 *
 * @author  Chris Warth
 * @version 1.89, 10/10/06
 * @see     java.net.InetAddress#getByAddress(byte[])
 * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 * @see     java.net.InetAddress#getAllByName(java.lang.String)
 * @see     java.net.InetAddress#getByName(java.lang.String)
 * @see     java.net.InetAddress#getLocalHost()
 * @since JDK1.0
 */
public
class InetAddress implements java.io.Serializable {
    /** 
     * Specify the address family: Internet Protocol, Version 4
     * @since 1.4
     */
    static final int IPv4 = 1;

    /** 
     * Specify the address family: Internet Protocol, Version 6
     * @since 1.4
     */
    static final int IPv6 = 2;

    /* Specify address family preference */
    static transient boolean preferIPv6Address = false;

    /**
     * @serial
     */
    String hostName;

    /**
     * Holds a 32-bit IPv4 address.
     *
     * @serial
     */
    int address;

    /**
     * Specifies the address family type, for instance, '1' for IPv4
     * addresses, and '2' for IPv6 addresses.
     *
     * @serial
     */
    int family;

    /* Used to store the name service provider */
    private static NameService nameService = null; 

    /* Used to store the best available hostname */
    private transient String canonicalHostName = null;

    /** use serialVersionUID from JDK 1.0.2 for interoperability */
    private static final long serialVersionUID = 3286316764910316507L;

    /*
     * Load net library into runtime, and perform initializations.
     */
    static {
	preferIPv6Address = 
	    ((Boolean)java.security.AccessController.doPrivileged(
		 new GetBooleanAction("java.net.preferIPv6Addresses"))).booleanValue();
	AccessController.doPrivileged(new LoadLibraryAction("net"));
        /*
         * Wrap the init() method in a privileged block so that it
         * can read system properties. In j2se1.4.2 this is done
         * in the InetAddress OnLoad() function & this is executed
         * by the system class loader.
         */
        java.security.AccessController.doPrivileged(
                      new java.security.PrivilegedAction() {
                          public Object run() 
                          {
                            init();
                            return null;
                          }
                        } );
    }

    /**
     * Constructor for the Socket.accept() method.
     * This creates an empty InetAddress, which is filled in by
     * the accept() method.  This InetAddress, however, is not
     * put in the address cache, since it is not created by name.
     */
    InetAddress() {
    }

    /**
     * Replaces the de-serialized object with an Inet4Address object.
     *
     * @return the alternate object to the de-serialized object.
     *
     * @throws ObjectStreamException if a new object replacing this
     * object could not be created
     */
    private Object readResolve() throws ObjectStreamException {
	// will replace the deserialized 'this' object
	return new Inet4Address(this.hostName, this.address); 
    }

    /**
     * Utility routine to check if the InetAddress is an
     * IP multicast address.
     * @return a <code>boolean</code> indicating if the InetAddress is 
     * an IP multicast address
     * @since   JDK1.1
     */
    public boolean isMulticastAddress() {
	return false;
    }

    /**
     * Utility routine to check if the InetAddress in a wildcard address.
     * @return a <code>boolean</code> indicating if the Inetaddress is
     *         a wildcard address.
     * @since 1.4
     */    
    public boolean isAnyLocalAddress() {
	return false;
    }

    /**
     * Utility routine to check if the InetAddress is a loopback address. 
     *
     * @return a <code>boolean</code> indicating if the InetAddress is 
     * a loopback address; or false otherwise.
     * @since 1.4
     */
    public boolean isLoopbackAddress() {
	return false;
    }

    /**
     * Utility routine to check if the InetAddress is an link local address. 
     *
     * @return a <code>boolean</code> indicating if the InetAddress is 
     * a link local address; or false if address is not a link local unicast address.
     * @since 1.4
     */
    public boolean isLinkLocalAddress() {
	return false;
    }

    /**
     * Utility routine to check if the InetAddress is a site local address. 
     *
     * @return a <code>boolean</code> indicating if the InetAddress is 
     * a site local address; or false if address is not a site local unicast address.
     * @since 1.4
     */
    public boolean isSiteLocalAddress() {
	return false;
    }

    /**
     * Utility routine to check if the multicast address has global scope.
     *
     * @return a <code>boolean</code> indicating if the address has 
     *         is a multicast address of global scope, false if it is not 
     *         of global scope or it is not a multicast address
     * @since 1.4
     */
    public boolean isMCGlobal() {
	return false;
    }

    /**
     * Utility routine to check if the multicast address has node scope.
     *
     * @return a <code>boolean</code> indicating if the address has 
     *         is a multicast address of node-local scope, false if it is not 
     *         of node-local scope or it is not a multicast address
     * @since 1.4
     */
    public boolean isMCNodeLocal() {
	return false;
    }

    /**
     * Utility routine to check if the multicast address has link scope.
     *
     * @return a <code>boolean</code> indicating if the address has 
     *         is a multicast address of link-local scope, false if it is not 
     *         of link-local scope or it is not a multicast address
     * @since 1.4
     */
    public boolean isMCLinkLocal() {
	return false;
    }

    /**
     * Utility routine to check if the multicast address has site scope.
     *
     * @return a <code>boolean</code> indicating if the address has 
     *         is a multicast address of site-local scope, false if it is not 
     *         of site-local scope or it is not a multicast address
     * @since 1.4
     */
    public boolean isMCSiteLocal() {
	return false;
    }

    /**
     * Utility routine to check if the multicast address has organization scope.
     *
     * @return a <code>boolean</code> indicating if the address has 
     *         is a multicast address of organization-local scope, 
     *         false if it is not of organization-local scope 
     *         or it is not a multicast address
     * @since 1.4
     */
    public boolean isMCOrgLocal() {
	return false;
    }

    /**
     * Gets the host name for this IP address.
     *
     * <p>If this InetAddress was created with a host name,
     * this host name will be remembered and returned; 
     * otherwise, a reverse name lookup will be performed
     * and the result will be returned based on the system 
     * configured name lookup service. If a lookup of the name service
     * is required, call 
     * {@link #getCanonicalHostName() getCanonicalHostName}.
     *
     * <p>If there is a security manager, its
     * <code>checkConnect</code> method is first called
     * with the hostname and <code>-1</code> 
     * as its arguments to see if the operation is allowed.
     * If the operation is not allowed, it will return
     * the textual representation of the IP address.
     *
     * @return  the host name for this IP address, or if the operation
     *    is not allowed by the security check, the textual 
     *    representation of the IP address.
     * 
     * @see InetAddress#getCanonicalHostName
     * @see SecurityManager#checkConnect
     */
    public String getHostName() {
	return getHostName(true);
    }

    /**
     * Returns the hostname for this address.
     * If the host is equal to null, then this address refers to any
     * of the local machine's available network addresses.
     * this is package private so SocketPermission can make calls into
     * here without a security check.
     *
     * <p>If there is a security manager, this method first
     * calls its <code>checkConnect</code> method
     * with the hostname and <code>-1</code> 
     * as its arguments to see if the calling code is allowed to know
     * the hostname for this IP address, i.e., to connect to the host.
     * If the operation is not allowed, it will return
     * the textual representation of the IP address.
     * 
     * @return  the host name for this IP address, or if the operation
     *    is not allowed by the security check, the textual 
     *    representation of the IP address.
     * 
     * @param check make security check if true
     * 
     * @see SecurityManager#checkConnect
     */
    String getHostName(boolean check) {
	if (hostName == null) {
	    hostName = InetAddress.getHostFromNameService(this, check);
	}