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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.net.InetAddress
public class InetAddress
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).
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.
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.
For IPv4 address format, please refer to Inet4Address#format; For IPv6 address format, please refer to Inet6Address#format.
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 vice versa.
By default, when a security manager is installed, in order to protect against DNS spoofing attacks, the result of positive host name resolutions are cached forever. When a security manager is not installed, the default behavior is to cache entries for a finite (implementation dependent) period of time. The result of unsuccessful host name resolution is cached for a very short period of time (10 seconds) to improve performance.
If the default behavior is not desired, then 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
- 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. The default setting is to cache for an implementation specific period of time.
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".
getByAddress(byte[])
,
getByAddress(java.lang.String, byte[])
,
getAllByName(java.lang.String)
,
getByName(java.lang.String)
,
getLocalHost()
,
Serialized FormMethod Summary | |
---|---|
boolean |
equals(Object obj)
Compares this object against the specified object. |
byte[] |
getAddress()
Returns the raw IP address of this InetAddress
object. |
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. |
static InetAddress |
getByAddress(byte[] addr)
Returns an InetAddress object given the raw IP address . |
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. |
static InetAddress |
getByName(String host)
Determines the IP address of a host, given the host's name. |
String |
getCanonicalHostName()
Gets the fully qualified domain name for this IP address. |
String |
getHostAddress()
Returns the IP address string in textual presentation. |
String |
getHostName()
Gets the host name for this IP address. |
static InetAddress |
getLocalHost()
Returns the local host. |
int |
hashCode()
Returns a hashcode for this IP address. |
boolean |
isAnyLocalAddress()
Utility routine to check if the InetAddress in a wildcard address. |
boolean |
isLinkLocalAddress()
Utility routine to check if the InetAddress is an link local address. |
boolean |
isLoopbackAddress()
Utility routine to check if the InetAddress is a loopback address. |
boolean |
isMCGlobal()
Utility routine to check if the multicast address has global scope. |
boolean |
isMCLinkLocal()
Utility routine to check if the multicast address has link scope. |
boolean |
isMCNodeLocal()
Utility routine to check if the multicast address has node scope. |
boolean |
isMCOrgLocal()
Utility routine to check if the multicast address has organization scope. |
boolean |
isMCSiteLocal()
Utility routine to check if the multicast address has site scope. |
boolean |
isMulticastAddress()
Utility routine to check if the InetAddress is an IP multicast address. |
boolean |
isReachable(int timeout)
Test whether that address is reachable. |
boolean |
isReachable(NetworkInterface netif,
int ttl,
int timeout)
Test whether that address is reachable. |
boolean |
isSiteLocalAddress()
Utility routine to check if the InetAddress is a site local address. |
String |
toString()
Converts this IP address to a String . |
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Method Detail |
---|
public boolean isMulticastAddress()
boolean
indicating if the InetAddress is
an IP multicast addresspublic boolean isAnyLocalAddress()
boolean
indicating if the Inetaddress is
a wildcard address.public boolean isLoopbackAddress()
boolean
indicating if the InetAddress is
a loopback address; or false otherwise.public boolean isLinkLocalAddress()
boolean
indicating if the InetAddress is
a link local address; or false if address is not a link local unicast address.public boolean isSiteLocalAddress()
boolean
indicating if the InetAddress is
a site local address; or false if address is not a site local unicast address.public boolean isMCGlobal()
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 addresspublic boolean isMCNodeLocal()
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 addresspublic boolean isMCLinkLocal()
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 addresspublic boolean isMCSiteLocal()
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 addresspublic boolean isMCOrgLocal()
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 addresspublic boolean isReachable(int timeout) throws IOException
The timeout value, in milliseconds, indicates the maximum amount of time the try should take. If the operation times out before getting an answer, the host is deemed unreachable. A negative value will result in an IllegalArgumentException being thrown.
timeout
- the time, in milliseconds, before the call aborts
boolean
indicating if the address is reachable.
IOException
- if a network error occurs
IllegalArgumentException
- if timeout
is negative.public boolean isReachable(NetworkInterface netif, int ttl, int timeout) throws IOException
The network interface
and ttl
parameters
let the caller specify which network interface the test will go through
and the maximum number of hops the packets should go through.
A negative value for the ttl
will result in an
IllegalArgumentException being thrown.
The timeout value, in milliseconds, indicates the maximum amount of time the try should take. If the operation times out before getting an answer, the host is deemed unreachable. A negative value will result in an IllegalArgumentException being thrown.
netif
- the NetworkInterface through which the
test will be done, or null for any interfacettl
- the maximum numbers of hops to try or 0 for the
defaulttimeout
- the time, in milliseconds, before the call aborts
boolean
indicating if the address is reachable.
IllegalArgumentException
- if either timeout
or ttl
are negative.
IOException
- if a network error occurspublic String getHostName()
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
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.
getCanonicalHostName()
,
SecurityManager.checkConnect(java.lang.String, int)
public String getCanonicalHostName()
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.
SecurityManager.checkConnect(java.lang.String, int)
public byte[] getAddress()
InetAddress
object. The result is in network byte order: the highest order
byte of the address is in getAddress()[0]
.
public String getHostAddress()
public int hashCode()
hashCode
in class Object
Object.equals(java.lang.Object)
,
Hashtable
public boolean equals(Object obj)
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.
equals
in class Object
obj
- the object to compare against.
true
if the objects are the same;
false
otherwise.getAddress()
public String toString()
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.
toString
in class Object
public static InetAddress getByAddress(String host, byte[] addr) throws UnknownHostException
The host name can either be a machine name, such as
"java.sun.com
", or a textual representation of its IP
address.
No validity checking is done on the host name either.
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
host
- the specified hostaddr
- the raw IP address in network byte order
UnknownHostException
- if IP address is of illegal lengthpublic static InetAddress getByName(String host) throws UnknownHostException
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. IPv6 scoped addresses are also
supported. See here for a description of IPv6
scoped addresses.
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.
host
- the specified host, or null
.
UnknownHostException
- if no IP address for the
host
could be found, or if a scope_id was specified
for a global IPv6 address.
SecurityException
- if a security manager exists
and its checkConnect method doesn't allow the operationpublic static InetAddress[] getAllByName(String host) throws UnknownHostException
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. A literal IPv6 address may
also be qualified by appending a scoped zone identifier or scope_id.
The syntax and usage of scope_ids is described
here.
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.
host
- the name of the host, or null
.
UnknownHostException
- if no IP address for the
host
could be found, or if a scope_id was specified
for a global IPv6 address.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.SecurityManager.checkConnect(java.lang.String, int)
public static InetAddress getByAddress(byte[] addr) throws UnknownHostException
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
addr
- the raw IP address in network byte order
UnknownHostException
- if IP address is of illegal lengthpublic static InetAddress getLocalHost() throws UnknownHostException
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.
UnknownHostException
- if no IP address for the
host
could be found.SecurityManager.checkConnect(java.lang.String, int)
|
Java™ Platform Standard Ed. 6 |
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