NetUtil (Netty API Reference (4.1.115.Final))

java.lang.Object
- io.netty.util.NetUtil

```
public final class NetUtil
extends Object
```
A class that holds a number of network-related constants.
This class borrowed some of its methods from a modified fork of the Inet6Util class which was part of Apache Harmony.

Field Summary

Fields
Modifier and Type	Field and Description
`static InetAddress`	`LOCALHOST` The `InetAddress` that represents the loopback address.
`static Inet4Address`	`LOCALHOST4` The `Inet4Address` that represents the IPv4 loopback address '127.0.0.1'
`static Inet6Address`	`LOCALHOST6` The `Inet6Address` that represents the IPv6 loopback address '::1'
`static NetworkInterface`	`LOOPBACK_IF` The loopback `NetworkInterface` of the current machine
`static Collection<NetworkInterface>`	`NETWORK_INTERFACES` An unmodifiable Collection of all the interfaces on this machine.
`static int`	`SOMAXCONN` The SOMAXCONN value of the current machine.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static String`	`bytesToIpAddress(byte[] bytes)` Converts 4-byte or 16-byte data into an IPv4 or IPv6 string respectively.
`static String`	`bytesToIpAddress(byte[] bytes, int offset, int length)` Converts 4-byte or 16-byte data into an IPv4 or IPv6 string respectively.
`static byte[]`	`createByteArrayFromIpAddressString(String ipAddressString)` Creates an byte[] based on an ipAddressString.
`static InetAddress`	`createInetAddressFromIpAddressString(String ipAddressString)` Creates an `InetAddress` based on an ipAddressString or might return null if it can't be parsed.
`static Inet6Address`	`getByName(CharSequence ip)` Returns the `Inet6Address` representation of a `CharSequence` IP address.
`static Inet6Address`	`getByName(CharSequence ip, boolean ipv4Mapped)` Returns the `Inet6Address` representation of a `CharSequence` IP address.
`static String`	`getHostname(InetSocketAddress addr)` Returns `InetSocketAddress.getHostString()` if Java >= 7, or `InetSocketAddress.getHostName()` otherwise.
`static String`	`intToIpAddress(int i)` Converts a 32-bit integer into an IPv4 address.
`static int`	`ipv4AddressToInt(Inet4Address ipAddress)` Convert `Inet4Address` into `int`
`static boolean`	`isIpV4StackPreferred()` Returns `true` if IPv4 should be used even if the system supports both IPv4 and IPv6.
`static boolean`	`isIpV6AddressesPreferred()` Returns `true` if an IPv6 address should be preferred when a host has both an IPv4 address and an IPv6 address.
`static boolean`	`isValidIpV4Address(CharSequence ip)` Takes a `CharSequence` and parses it to see if it is a valid IPV4 address.
`static boolean`	`isValidIpV4Address(String ip)` Takes a `String` and parses it to see if it is a valid IPV4 address.
`static boolean`	`isValidIpV6Address(CharSequence ip)`
`static boolean`	`isValidIpV6Address(String ip)`
`static String`	`toAddressString(InetAddress ip)` Returns the `String` representation of an `InetAddress`.
`static String`	`toAddressString(InetAddress ip, boolean ipv4Mapped)` Returns the `String` representation of an `InetAddress`.
`static String`	`toSocketAddressString(InetSocketAddress addr)` Returns the `String` representation of an `InetSocketAddress`.
`static String`	`toSocketAddressString(String host, int port)` Returns the `String` representation of a host port combo.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LOCALHOST4
```
public static final Inet4Address LOCALHOST4
```
    The Inet4Address that represents the IPv4 loopback address '127.0.0.1'
  - LOCALHOST6
```
public static final Inet6Address LOCALHOST6
```
    The Inet6Address that represents the IPv6 loopback address '::1'
  - LOCALHOST
```
public static final InetAddress LOCALHOST
```
    The InetAddress that represents the loopback address. If IPv6 stack is available, it will refer to LOCALHOST6. Otherwise, LOCALHOST4.
  - LOOPBACK_IF
```
public static final NetworkInterface LOOPBACK_IF
```
    The loopback NetworkInterface of the current machine
  - NETWORK_INTERFACES
```
public static final Collection<NetworkInterface> NETWORK_INTERFACES
```
    An unmodifiable Collection of all the interfaces on this machine.
  - SOMAXCONN
```
public static final int SOMAXCONN
```
    The SOMAXCONN value of the current machine. If failed to get the value, 200 is used as a default value for Windows and 128 for others.
- Method Detail
  - isIpV4StackPreferred
```
public static boolean isIpV4StackPreferred()
```
    Returns true if IPv4 should be used even if the system supports both IPv4 and IPv6. Setting this property to true will disable IPv6 support. The default value of this property is false.
    
    See Also:
    
    Java SE networking properties
  - isIpV6AddressesPreferred
```
public static boolean isIpV6AddressesPreferred()
```
    Returns true if an IPv6 address should be preferred when a host has both an IPv4 address and an IPv6 address. The default value of this property is false.
    
    See Also:
    
    Java SE networking properties
  - createByteArrayFromIpAddressString
```
public static byte[] createByteArrayFromIpAddressString(String ipAddressString)
```
    Creates an byte[] based on an ipAddressString. No error handling is performed here.
  - createInetAddressFromIpAddressString
```
public static InetAddress createInetAddressFromIpAddressString(String ipAddressString)
```
    Creates an InetAddress based on an ipAddressString or might return null if it can't be parsed. No error handling is performed here.
  - ipv4AddressToInt
```
public static int ipv4AddressToInt(Inet4Address ipAddress)
```
    Convert Inet4Address into int
  - intToIpAddress
```
public static String intToIpAddress(int i)
```
    Converts a 32-bit integer into an IPv4 address.
  - bytesToIpAddress
```
public static String bytesToIpAddress(byte[] bytes)
```
    Converts 4-byte or 16-byte data into an IPv4 or IPv6 string respectively.
    
    Throws:
    
    IllegalArgumentException - if length is not 4 nor 16
  - bytesToIpAddress
```
public static String bytesToIpAddress(byte[] bytes,
                                      int offset,
                                      int length)
```
    Converts 4-byte or 16-byte data into an IPv4 or IPv6 string respectively.
    
    Throws:
    
    IllegalArgumentException - if length is not 4 nor 16
  - isValidIpV6Address
```
public static boolean isValidIpV6Address(String ip)
```
  - isValidIpV6Address
```
public static boolean isValidIpV6Address(CharSequence ip)
```
  - isValidIpV4Address
```
public static boolean isValidIpV4Address(CharSequence ip)
```
    Takes a CharSequence and parses it to see if it is a valid IPV4 address.
    
    Returns:
    
    true, if the string represents an IPV4 address in dotted notation, false otherwise
  - isValidIpV4Address
```
public static boolean isValidIpV4Address(String ip)
```
    Takes a String and parses it to see if it is a valid IPV4 address.
    
    Returns:
    
    true, if the string represents an IPV4 address in dotted notation, false otherwise
  - getByName
```
public static Inet6Address getByName(CharSequence ip)
```
    Returns the Inet6Address representation of a CharSequence IP address.
    This method will treat all IPv4 type addresses as "IPv4 mapped" (see getByName(CharSequence, boolean))
    
    Parameters:
    
    ip - CharSequence IP address to be converted to a Inet6Address
    
    Returns:
    
    Inet6Address representation of the ip or null if not a valid IP address.
  - getByName
```
public static Inet6Address getByName(CharSequence ip,
                                     boolean ipv4Mapped)
```
    Returns the Inet6Address representation of a CharSequence IP address.
    The ipv4Mapped parameter specifies how IPv4 addresses should be treated. "IPv4 mapped" format as defined in rfc 4291 section 2 is supported.
    Parameters:
    
    ip - CharSequence IP address to be converted to a Inet6Address
    ipv4Mapped -
    
    true To allow IPv4 mapped inputs to be translated into Inet6Address
    
    false Consider IPv4 mapped addresses as invalid.
    Returns:
    
    Inet6Address representation of the ip or null if not a valid IP address.
  - toSocketAddressString
```
public static String toSocketAddressString(InetSocketAddress addr)
```
    Returns the String representation of an InetSocketAddress.
    The output does not include Scope ID.
    
    Parameters:
    
    addr - InetSocketAddress to be converted to an address string
    
    Returns:
    
    String containing the text-formatted IP address
  - toSocketAddressString
```
public static String toSocketAddressString(String host,
                                           int port)
```
    Returns the String representation of a host port combo.
  - toAddressString
```
public static String toAddressString(InetAddress ip)
```
    Returns the String representation of an InetAddress.
    - Inet4Address results are identical to InetAddress.getHostAddress()
    - Inet6Address results adhere to rfc 5952 section 4
    The output does not include Scope ID.
    Parameters:
    
    ip - InetAddress to be converted to an address string
    
    Returns:
    
    String containing the text-formatted IP address
  - toAddressString
```
public static String toAddressString(InetAddress ip,
                                     boolean ipv4Mapped)
```
    Returns the String representation of an InetAddress.
    - Inet4Address results are identical to InetAddress.getHostAddress()
    - Inet6Address results adhere to rfc 5952 section 4 if ipv4Mapped is false. If ipv4Mapped is true then "IPv4 mapped" format from rfc 4291 section 2 will be supported. The compressed result will always obey the compression rules defined in rfc 5952 section 4
    The output does not include Scope ID.
    Parameters:
    
    ip - InetAddress to be converted to an address string
    ipv4Mapped -
    
    true to stray from strict rfc 5952 and support the "IPv4 mapped" format defined in rfc 4291 section 2 while still following the updated guidelines in rfc 5952 section 4
    
    false to strictly follow rfc 5952
    Returns:
    
    String containing the text-formatted IP address
  - getHostname
```
public static String getHostname(InetSocketAddress addr)
```
    Returns InetSocketAddress.getHostString() if Java >= 7, or InetSocketAddress.getHostName() otherwise.
    
    Parameters:
    
    addr - The address
    
    Returns:
    
    the host string

Class NetUtil

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOCALHOST4

LOCALHOST6

LOCALHOST

LOOPBACK_IF

NETWORK_INTERFACES

SOMAXCONN

Method Detail

isIpV4StackPreferred

isIpV6AddressesPreferred

createByteArrayFromIpAddressString

createInetAddressFromIpAddressString

ipv4AddressToInt

intToIpAddress

bytesToIpAddress

bytesToIpAddress

isValidIpV6Address

isValidIpV6Address

isValidIpV4Address

isValidIpV4Address

getByName

getByName

toSocketAddressString

toSocketAddressString

toAddressString

toAddressString

getHostname