| java.lang.Object
 java.net.InetAddress
All known Subclasses: java.net.Inet6Address, java.net.Inet4Address,
| InetAddress | | public class InetAddress implements java.io.Serializable(Code) | | This class represents an Internet Protocol (IP) address.
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 RFC 790:
Assigned Numbers, RFC 1918:
Address Allocation for Private Internets, RFC 2365:
Administratively Scoped IP Multicast, and RFC 2373: IP
Version 6 Addressing Architecture. 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).
Address types
| unicast |
An identifier for a single interface. A packet sent to
a unicast address is delivered to the interface identified by
that address.
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.
The unspecified address must not be used as
the destination address of an IP packet.
The Loopback 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. |
|---|
| multicast |
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. |
|---|
IP address scope
Link-local 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.
Site-local addresses are designed to be used for addressing
inside of a site without the need for a global prefix.
Global addresses are unique across the internet.
Textual representation of IP addresses
The textual representation of an IP address is address family specific.
For IPv4 address format, please refer to Inet4Address#format; For IPv6
address format, please refer to Inet6Address#format.
Host Name Resolution
Host name-to-IP address resolution 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.
Reverse name resolution means that for any IP address,
the host associated with the IP address is returned.
The InetAddress class provides methods to resolve host names to
their IP addresses and vise versa.
InetAddress Caching
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.
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.
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.
Two Java security properties control the TTL values used for
positive and negative host name resolution caching:
- networkaddress.cache.ttl (default: -1)
- 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.
A value of -1 indicates "cache forever".
- networkaddress.cache.negative.ttl (default: 10)
- 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.
A value of 0 indicates "never cache".
A value of -1 indicates "cache forever".
author:
Chris Warth
version:
1.89, 10/10/06
See Also: java.net.InetAddress.getByAddress(byte[])
See Also: java.net.InetAddress.getByAddress(java.lang.Stringbyte[])
See Also: java.net.InetAddress.getAllByName(java.lang.String)
See Also: java.net.InetAddress.getByName(java.lang.String)
See Also: java.net.InetAddress.getLocalHost
since:
JDK1.0 |
| Inner Class :final static class CacheEntry | |
| Inner Class :final static class Cache | |
| Constructor Summary | |
| | InetAddress()
Constructor for the Socket.accept() method.
This creates an empty InetAddress, which is filled in by
the accept() method. |
| Method Summary | |
| static InetAddress | anyLocalAddress()
| | public boolean | equals(Object obj)
Compares this object against the specified object.
The result is true if and only if the argument is
not null and it represents the same IP address as
this object.
Two instances of InetAddress represent the same IP
address if the length of the byte arrays returned by
getAddress is the same for both, and each of the
array components is the same for the byte arrays.
Parameters:
obj - the object to compare against. | | public byte[] | getAddress()
Returns the raw IP address of this InetAddress
object. | | public static InetAddress[] | getAllByName(String host)
Given the name of a host, returns an array of its IP addresses,
based on the configured name service on the system.
The host name can either be a machine name, such as
"java.sun.com", or a textual representation of its IP
address. | | static InetAddress[] | getAllByName0(String host, boolean check)
| | public static InetAddress | getByAddress(String host, byte[] addr)
Create an InetAddress based on the provided host name and IP address
No name service is checked for the validity of the address. | | public static InetAddress | getByAddress(byte[] addr)
Returns an InetAddress object given the raw IP address . | | public static InetAddress | getByName(String host)
Determines the IP address of a host, given the host's name.
The host name can either be a machine name, such as
"java.sun.com", or a textual representation of its
IP address. | | public String | getCanonicalHostName()
Gets the fully qualified domain name for this IP address. | | public String | getHostAddress()
Returns the IP address string in textual presentation. | | public String | getHostName()
Gets the host name for this IP address.
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. | | String | getHostName(boolean check)
Returns the hostname for this address. | | public static InetAddress | getLocalHost()
Returns the local host.
If there is a security manager, its
checkConnect method is called
with the local host name and -1
as its arguments to see if the operation is allowed. | | public int | hashCode()
Returns a hashcode for this IP address. | | public boolean | isAnyLocalAddress()
Utility routine to check if the InetAddress in a wildcard address. | | public boolean | isLinkLocalAddress()
Utility routine to check if the InetAddress is an link local address. | | public boolean | isLoopbackAddress()
Utility routine to check if the InetAddress is a loopback address. | | public boolean | isMCGlobal()
Utility routine to check if the multicast address has global scope. | | public boolean | isMCLinkLocal()
Utility routine to check if the multicast address has link scope. | | public boolean | isMCNodeLocal()
Utility routine to check if the multicast address has node scope. | | public boolean | isMCOrgLocal()
Utility routine to check if the multicast address has organization scope. | | public boolean | isMCSiteLocal()
Utility routine to check if the multicast address has site scope. | | public boolean | isMulticastAddress()
Utility routine to check if the InetAddress is an
IP multicast address. | | public boolean | isSiteLocalAddress()
Utility routine to check if the InetAddress is a site local address. | | static Object | loadImpl(String implName)
| | public String | toString()
Converts this IP address to a String. |
| IPv4 | | final static int IPv4(Code) | | Specify the address family: Internet Protocol, Version 4
since:
1.4 |
| IPv6 | | final static int IPv6(Code) | | Specify the address family: Internet Protocol, Version 6
since:
1.4 |
| address | | int address(Code) | | Holds a 32-bit IPv4 address.
|
| family | | int family(Code) | | Specifies the address family type, for instance, '1' for IPv4
addresses, and '2' for IPv6 addresses.
|
| preferIPv6Address | | static transient boolean preferIPv6Address(Code) | | |
| InetAddress | | InetAddress()(Code) | | 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.
|
| equals | | public boolean equals(Object obj)(Code) | | Compares this object against the specified object.
The result is true if and only if the argument is
not null and it represents the same IP address as
this object.
Two instances of InetAddress represent the same IP
address if the length of the byte arrays returned by
getAddress is the same for both, and each of the
array components is the same for the byte arrays.
Parameters:
obj - the object to compare against. true if the objects are the same;false otherwise.
See Also: java.net.InetAddress.getAddress |
| getAddress | | public byte[] getAddress()(Code) | | Returns the raw IP address of this InetAddress
object. The result is in network byte order: the highest order
byte of the address is in getAddress()[0].
the raw IP address of this object. |
| getAllByName | | public static InetAddress[] getAllByName(String host) throws UnknownHostException(Code) | | Given the name of a host, returns an array of its IP addresses,
based on the configured name service on the system.
The host name can either be a machine name, such as
"java.sun.com", or a textual representation of its IP
address. If a literal IP address is supplied, only the
validity of the address format is checked.
For host specified in literal IPv6 address,
either the form defined in RFC 2732 or the literal IPv6 address
format defined in RFC 2373 is accepted.
If the host is null then an InetAddress
representing an address of the loopback interface is returned.
See RFC 3330
section 2 and RFC 2373
section 2.5.3.
If there is a security manager and host is not
null and host.length() is not equal to zero, the
security manager's
checkConnect method is called
with the hostname and -1
as its arguments to see if the operation is allowed.
Parameters:
host - the name of the host, or null. an array of all the IP addresses for a given host name.
exception:
UnknownHostException - if no IP address for thehost could be found.
exception:
SecurityException - if a security manager exists and its checkConnect method doesn't allow the operation.
See Also: SecurityManager.checkConnect |
| getByAddress | | public static InetAddress getByAddress(String host, byte[] addr) throws UnknownHostException(Code) | | Create an InetAddress based on the provided host name and IP address
No name service is checked for the validity of the address.
The host name can either be a machine name, such as
"java.sun.com", or a textual representation of its IP
address.
For host specified in literal IPv6 address,
either the form defined in RFC 2732 or the literal IPv6 address
format defined in RFC 2373 is accepted.
If addr specifies an IPv4 address an instance of Inet4Address
will be returned; otherwise, an instance of Inet6Address
will be returned.
IPv4 address byte array must be 4 bytes long and IPv6 byte array
must be 16 bytes long
Parameters:
host - the specified host
Parameters:
addr - the raw IP address in network byte order an InetAddress object created from the raw IP address.
exception:
UnknownHostException - if IP address is of illegal length
since:
1.4 |
| getByAddress | | public static InetAddress getByAddress(byte[] addr) throws UnknownHostException(Code) | | Returns an InetAddress object given the raw IP address .
The argument is in network byte order: the highest order
byte of the address is in getAddress()[0].
This method doesn't block, i.e. no reverse name service lookup
is performed.
IPv4 address byte array must be 4 bytes long and IPv6 byte array
must be 16 bytes long
Parameters:
addr - the raw IP address in network byte order an InetAddress object created from the raw IP address.
exception:
UnknownHostException - if IP address is of illegal length
since:
1.4 |
| getByName | | public static InetAddress getByName(String host) throws UnknownHostException(Code) | | Determines the IP address of a host, given the host's name.
The host name can either be a machine name, such as
"java.sun.com", or a textual representation of its
IP address. If a literal IP address is supplied, only the
validity of the address format is checked.
For host specified in literal IPv6 address,
either the form defined in RFC 2732 or the literal IPv6 address
format defined in RFC 2373 is accepted.
If the host is null then an InetAddress
representing an address of the loopback interface is returned.
See RFC 3330
section 2 and RFC 2373
section 2.5.3.
Parameters:
host - the specified host, or null. an IP address for the given host name.
exception:
UnknownHostException - if no IP address for thehost could be found.
exception:
SecurityException - if a security manager existsand its checkConnect method doesn't allow the operation |
| getCanonicalHostName | | public String getCanonicalHostName()(Code) | | Gets the fully qualified domain name for this IP address.
Best effort method, meaning we may not be able to return
the FQDN depending on the underlying system configuration.
If there is a security manager, this method first
calls its checkConnect method
with the hostname and -1
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.
the fully qualified domain name for this IP address, or if the operation is not allowed by the security check,the textual representation of the IP address.
See Also: SecurityManager.checkConnect
since:
1.4 |
| getHostAddress | | public String getHostAddress()(Code) | | Returns the IP address string in textual presentation.
the raw IP address in a string format.
since:
JDK1.0.2 |
| getHostName | | public String getHostName()(Code) | | Gets the host name for this IP address.
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
InetAddress.getCanonicalHostName() getCanonicalHostName .
If there is a security manager, its
checkConnect method is first called
with the hostname and -1
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.
the host name for this IP address, or if the operationis not allowed by the security check, the textual representation of the IP address.
See Also: InetAddress.getCanonicalHostName
See Also: SecurityManager.checkConnect |
| getHostName | | String getHostName(boolean check)(Code) | | 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.
If there is a security manager, this method first
calls its checkConnect method
with the hostname and -1
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.
the host name for this IP address, or if the operationis not allowed by the security check, the textual representation of the IP address.
Parameters:
check - make security check if true
See Also: SecurityManager.checkConnect |
| getLocalHost | | public static InetAddress getLocalHost() throws UnknownHostException(Code) | | Returns the local host.
If there is a security manager, its
checkConnect method is called
with the local host name and -1
as its arguments to see if the operation is allowed.
If the operation is not allowed, an InetAddress representing
the loopback address is returned.
the IP address of the local host.
exception:
UnknownHostException - if no IP address for thehost could be found.
See Also: SecurityManager.checkConnect |
| hashCode | | public int hashCode()(Code) | | Returns a hashcode for this IP address.
a hash code value for this IP address. |
| isAnyLocalAddress | | public boolean isAnyLocalAddress()(Code) | | Utility routine to check if the InetAddress in a wildcard address.
a boolean indicating if the Inetaddress isa wildcard address.
since:
1.4 |
| isLinkLocalAddress | | public boolean isLinkLocalAddress()(Code) | | Utility routine to check if the InetAddress is an link local address.
a boolean indicating if the InetAddress is a link local address; or false if address is not a link local unicast address.
since:
1.4 |
| isLoopbackAddress | | public boolean isLoopbackAddress()(Code) | | Utility routine to check if the InetAddress is a loopback address.
a boolean indicating if the InetAddress is a loopback address; or false otherwise.
since:
1.4 |
| isMCGlobal | | public boolean isMCGlobal()(Code) | | Utility routine to check if the multicast address has global scope.
a boolean 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 |
| isMCLinkLocal | | public boolean isMCLinkLocal()(Code) | | Utility routine to check if the multicast address has link scope.
a boolean 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 |
| isMCNodeLocal | | public boolean isMCNodeLocal()(Code) | | Utility routine to check if the multicast address has node scope.
a boolean 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 |
| isMCOrgLocal | | public boolean isMCOrgLocal()(Code) | | Utility routine to check if the multicast address has organization scope.
a boolean 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 |
| isMCSiteLocal | | public boolean isMCSiteLocal()(Code) | | Utility routine to check if the multicast address has site scope.
a boolean 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 |
| isMulticastAddress | | public boolean isMulticastAddress()(Code) | | Utility routine to check if the InetAddress is an
IP multicast address.
a boolean indicating if the InetAddress is an IP multicast address
since:
JDK1.1 |
| isSiteLocalAddress | | public boolean isSiteLocalAddress()(Code) | | Utility routine to check if the InetAddress is a site local address.
a boolean indicating if the InetAddress is a site local address; or false if address is not a site local unicast address.
since:
1.4 |
| toString | | public String toString()(Code) | | Converts this IP address to a String. The
string returned is of the form: hostname / literal IP
address.
If the host name is unresolved, no reverse name service loopup
is performed. The hostname part will be represented by an empty string.
a string representation of this IP address. |
|
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