Class NetworkInterface
A Network Interface is an abstraction encapsulating the characteristics of a Network Interface Controller, or Virtual Network adapter, which is a system hardware/software component connecting a computer, or host system, to a computer network. A Network Interface can be physical or virtual. A Network Interface has a name, zero or more assigned IP addresses, zero or more MAC Addresses, and may have an index. The name is highly platform specific but a name such as "le0" is typical; it may not be unique. The index is a highly platform specific number that identifies the interface. The network configuration may change during the lifetime of the JVM. For example, the set of IP addresses assigned to a network interface can be transient and dynamically allocated, and may change at any time.
When obtaining a NetworkInterface
instance, part of its
configuration (such as its name and the list of assigned IP addresses),
is reflective of its configuration at creation time.
Obtaining an updated view of the network configuration may require
looking up a network interface again in order to obtain a new instance.
Network interface instances are typically used to identify the local interface on which a multicast group is joined.
- API Note:
- Several static methods in this class are
factory methods, returning a new instance of a
NetworkInterface
, reflecting the configuration at the time of instantiation. The network configuration may change at any time, and as such, these methods may need to be invoked again in order to obtain a more up-to-date view of the network interfaces. In particular, there is no guarantee that the same interface will be found at the same index, or that the same network addresses will be bound to the interface, if the network configuration of the system has changed. - Since:
- 1.4
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Method Summary
Modifier and TypeMethodDescriptionboolean
Compares this object against the specified object.static NetworkInterface
getByIndex
(int index) Get a network interface given its index.static NetworkInterface
getByInetAddress
(InetAddress addr) Convenience method to search for a network interface that has the specified Internet Protocol (IP) address bound to it.static NetworkInterface
Searches for the network interface with the specified name.Get the display name of this network interface.byte[]
Returns the hardware address (usually MAC) of the interface if it has one and if it can be accessed given the current privileges.int
getIndex()
Returns the index of this network interface.Get an Enumeration of the InetAddresses bound to this network interface.Get a List of theInterfaceAddresses
of this network interface.int
getMTU()
Returns the Maximum Transmission Unit (MTU) of this interface.getName()
Get the name of this network interface.static Enumeration
<NetworkInterface> Returns anEnumeration
of all the interfaces on this machine.Returns the parent NetworkInterface of this interface if this is a subinterface, ornull
if it is a physical (non virtual) interface or has no parent.Get an Enumeration with all the subinterfaces (also known as virtual interfaces) attached to this network interface.Get a Stream of the InetAddresses bound to this network interface.boolean
Returns whether a network interface is a loopback interface.boolean
Returns whether a network interface is a point to point interface.boolean
isUp()
Returns whether a network interface is up and running.boolean
Returns whether this interface is a virtual interface (also called subinterface).static Stream
<NetworkInterface> Returns aStream
of all the interfaces on this machine.Get a Stream of all subinterfaces (also known as virtual interfaces) attached to this network interface.boolean
Returns whether a network interface supports multicasting or not.
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Method Details
-
getName
Get the name of this network interface.- Returns:
- the name of this network interface
-
getInetAddresses
Get an Enumeration of the InetAddresses bound to this network interface.- Implementation Note:
- The returned enumeration contains the InetAddresses that were bound to the interface at the time the interface configuration was read
- Returns:
- an Enumeration object with the InetAddresses bound to this network interface
- See Also:
-
inetAddresses
Get a Stream of the InetAddresses bound to this network interface.- Implementation Note:
- The stream contains the InetAddresses that were bound to the interface at the time the interface configuration was read
- Returns:
- a Stream object with the InetAddresses bound to this network interface
- Since:
- 9
-
getInterfaceAddresses
Get a List of theInterfaceAddresses
of this network interface.- Returns:
- a
List
object with the InterfaceAddress of this network interface - Since:
- 1.6
-
getSubInterfaces
Get an Enumeration with all the subinterfaces (also known as virtual interfaces) attached to this network interface.For instance eth0:1 will be a subinterface to eth0.
- Returns:
- an Enumeration object with all of the subinterfaces of this network interface
- Since:
- 1.6
- See Also:
-
subInterfaces
Get a Stream of all subinterfaces (also known as virtual interfaces) attached to this network interface.- Returns:
- a Stream object with all of the subinterfaces of this network interface
- Since:
- 9
-
getParent
Returns the parent NetworkInterface of this interface if this is a subinterface, ornull
if it is a physical (non virtual) interface or has no parent.- Returns:
- The
NetworkInterface
this interface is attached to. - Since:
- 1.6
-
getIndex
public int getIndex()Returns the index of this network interface. The index is an integer greater or equal to zero, or-1
for unknown. This is a system specific value and interfaces with the same name can have different indexes on different machines.- Returns:
- the index of this network interface or
-1
if the index is unknown - Since:
- 1.7
- See Also:
-
getDisplayName
Get the display name of this network interface. A display name is a human readable String describing the network device.- Returns:
- a non-empty string representing the display name of this network interface, or null if no display name is available.
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getByName
Searches for the network interface with the specified name.- API Note:
- The returned interface instance may reflect a snapshot of the configuration taken at the time the instance is created. See the general discussion of snapshots and configuration for the semantics of the returned interface.
- Parameters:
name
- The name of the network interface.- Returns:
- A
NetworkInterface
with the specified name, ornull
if there is no network interface with the specified name. - Throws:
SocketException
- If an I/O error occurs.NullPointerException
- If the specified name isnull
.
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getByIndex
Get a network interface given its index.- API Note:
- The returned interface instance may reflect a snapshot of the configuration taken at the time the instance is created. See the general discussion of snapshots and configuration for the semantics of the returned interface.
- Parameters:
index
- an integer, the index of the interface- Returns:
- the NetworkInterface obtained from its index, or
null
if there is no interface with such an index on the system - Throws:
SocketException
- if an I/O error occurs.IllegalArgumentException
- if index has a negative value- Since:
- 1.7
- See Also:
-
getByInetAddress
Convenience method to search for a network interface that has the specified Internet Protocol (IP) address bound to it.If the specified IP address is bound to multiple network interfaces it is not defined which network interface is returned.
- API Note:
- The returned interface instance may reflect a snapshot of the configuration taken at the time the instance is created. See the general discussion of snapshots and configuration for the semantics of the returned interface.
- Parameters:
addr
- TheInetAddress
to search with.- Returns:
- A
NetworkInterface
ornull
if there is no network interface with the specified IP address. - Throws:
SocketException
- If an I/O error occurs.NullPointerException
- If the specified address isnull
.
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getNetworkInterfaces
Returns anEnumeration
of all the interfaces on this machine. TheEnumeration
contains at least one element, possibly representing a loopback interface that only supports communication between entities on this machine.- API Note:
- This method can be used in combination with
getInetAddresses()
to obtain all IP addresses for this node.The returned interface instances may reflect a snapshot of the configuration taken at the time the instance is created. See the general discussion of snapshots and configuration for the semantics of the returned interface.
- Returns:
- an Enumeration of NetworkInterfaces found on this machine
- Throws:
SocketException
- if an I/O error occurs, or if the platform does not have at least one configured network interface.- See Also:
-
networkInterfaces
Returns aStream
of all the interfaces on this machine. TheStream
contains at least one interface, possibly representing a loopback interface that only supports communication between entities on this machine.- API Note:
- This method can be used in combination with
inetAddresses()
} to obtain a stream of all IP addresses for this node, for example:Stream<InetAddress> addrs = NetworkInterface.networkInterfaces() .flatMap(NetworkInterface::inetAddresses);
The returned interface instances may reflect a snapshot of the configuration taken at the time the instance is created. See the general discussion of snapshots and configuration for the semantics of the returned interface.
- Returns:
- a Stream of NetworkInterfaces found on this machine
- Throws:
SocketException
- if an I/O error occurs, or if the platform does not have at least one configured network interface.- Since:
- 9
-
isUp
Returns whether a network interface is up and running.- Returns:
true
if the interface is up and running.- Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
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isLoopback
Returns whether a network interface is a loopback interface.- Returns:
true
if the interface is a loopback interface.- Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
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isPointToPoint
Returns whether a network interface is a point to point interface. A typical point to point interface would be a PPP connection through a modem.- Returns:
true
if the interface is a point to point interface.- Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
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supportsMulticast
Returns whether a network interface supports multicasting or not.- Returns:
true
if the interface supports Multicasting.- Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
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getHardwareAddress
Returns the hardware address (usually MAC) of the interface if it has one and if it can be accessed given the current privileges.- Returns:
- a byte array containing the address, or
null
if the address doesn't exist or is not accessible - Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
-
getMTU
Returns the Maximum Transmission Unit (MTU) of this interface.- Returns:
- the value of the MTU for that interface.
- Throws:
SocketException
- if an I/O error occurs.- Since:
- 1.6
-
isVirtual
public boolean isVirtual()Returns whether this interface is a virtual interface (also called subinterface). Virtual interfaces are, on some systems, interfaces created as a child of a physical interface and given different settings (like address or MTU). Usually the name of the interface will the name of the parent followed by a colon (:) and a number identifying the child since there can be several virtual interfaces attached to a single physical interface.- Returns:
true
if this interface is a virtual interface.- Since:
- 1.6
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equals
Compares this object against the specified object. The result istrue
if and only if the argument is notnull
and it represents the same NetworkInterface as this object.Two instances of
NetworkInterface
represent the same NetworkInterface if both the name and the set ofInetAddress
es bound to the interfaces are equal.- Overrides:
equals
in classObject
- API Note:
- two
NetworkInterface
objects referring to the same underlying interface may not compare equal if the addresses of the underlying interface are being dynamically updated by the system. - Parameters:
obj
- the object to compare against.- Returns:
true
if the objects are the same;false
otherwise.- See Also:
-