NetUtil

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

```
public final class NetUtil
extends java.lang.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
`private static int`	`IPV4_BYTE_COUNT` Number of bytes needed to represent and IPV4 value
`private static int`	`IPV4_MAX_CHAR_BETWEEN_SEPARATOR` Maximum amount of value adding characters in between IPV4 separators
`private static boolean`	`IPV4_PREFERRED` `true` if ipv4 should be used on a system that supports ipv4 and ipv6.
`private static int`	`IPV4_SEPARATORS` Number of separators that must be present in an IPv4 string
`private static int`	`IPV6_BYTE_COUNT` Number of bytes needed to represent and IPV6 value
`private static int`	`IPV6_MAX_CHAR_BETWEEN_SEPARATOR` Maximum amount of value adding characters in between IPV6 separators
`private static int`	`IPV6_MAX_CHAR_COUNT` The maximum number of characters for an IPV6 string with no scope
`private static int`	`IPV6_MAX_SEPARATORS` Maximum number of separators that must be present in an IPv6 string
`private static int`	`IPV6_MIN_SEPARATORS` Minimum number of separators that must be present in an IPv6 string
`private static int`	`IPV6_WORD_COUNT` This defines how many words (represented as ints) are needed to represent an IPv6 address
`static java.net.InetAddress`	`LOCALHOST` The `InetAddress` that represents the loopback address.
`static java.net.Inet4Address`	`LOCALHOST4` The `Inet4Address` that represents the IPv4 loopback address '127.0.0.1'
`static java.net.Inet6Address`	`LOCALHOST6` The `Inet6Address` that represents the IPv6 loopback address '::1'
`private static InternalLogger`	`logger` The logger being used by this class
`static java.net.NetworkInterface`	`LOOPBACK_IF` The loopback `NetworkInterface` of the current machine
`static int`	`SOMAXCONN` The SOMAXCONN value of the current machine.

Constructor Summary

Constructors
Modifier Constructor and Description

private NetUtil()
A constructor to stop this class being constructed.

Constructors
Modifier	Constructor and Description
`private`	`NetUtil()` A constructor to stop this class being constructed.

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`private static void`	`convertToBytes(java.lang.String hexWord, byte[] ipByteArray, int byteIndex)` Converts a 4 character hex word into a 2 byte word equivalent
`static byte[]`	`createByteArrayFromIpAddressString(java.lang.String ipAddressString)` Creates an byte[] based on an ipAddressString.
`static java.net.Inet6Address`	`getByName(java.lang.CharSequence ip)` Returns the `Inet6Address` representation of a `CharSequence` IP address.
`static java.net.Inet6Address`	`getByName(java.lang.CharSequence ip, boolean ipv4Mapped)` Returns the `Inet6Address` representation of a `CharSequence` IP address.
`(package private) static int`	`getIntValue(char c)`
`private static boolean`	`inRangeEndExclusive(int value, int start, int end)` Does a range check on `value` if is within `start` (inclusive) and `end` (exclusive).
`static boolean`	`isIpV4StackPreferred()` Returns `true` if ipv4 should be prefered on a system that supports ipv4 and ipv6.
`private static boolean`	`isValidHexChar(char c)`
`static boolean`	`isValidIp4Word(java.lang.String word)` Deprecated. Do not use; published by mistake.
`static boolean`	`isValidIpV4Address(java.lang.String value)` Takes a string and parses it to see if it is a valid IPV4 address.
`static boolean`	`isValidIpV6Address(java.lang.String ipAddress)`
`private static boolean`	`isValidNumericChar(char c)`
`static java.lang.String`	`toAddressString(java.net.InetAddress ip)` Returns the `String` representation of an `InetAddress`.
`static java.lang.String`	`toAddressString(java.net.InetAddress ip, boolean ipv4Mapped)` Returns the `String` representation of an `InetAddress`.

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

- Field Detail
  - LOCALHOST4
```
public static final java.net.Inet4Address LOCALHOST4
```
    The Inet4Address that represents the IPv4 loopback address '127.0.0.1'
  - LOCALHOST6
```
public static final java.net.Inet6Address LOCALHOST6
```
    The Inet6Address that represents the IPv6 loopback address '::1'
  - LOCALHOST
```
public static final java.net.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 java.net.NetworkInterface LOOPBACK_IF
```
    The loopback NetworkInterface of the current 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 or 128 for others.
  - IPV6_WORD_COUNT
```
private static final int IPV6_WORD_COUNT
```
    This defines how many words (represented as ints) are needed to represent an IPv6 address
    
    See Also:
    
    Constant Field Values
  - IPV6_MAX_CHAR_COUNT
```
private static final int IPV6_MAX_CHAR_COUNT
```
    The maximum number of characters for an IPV6 string with no scope
    
    See Also:
    
    Constant Field Values
  - IPV6_BYTE_COUNT
```
private static final int IPV6_BYTE_COUNT
```
    Number of bytes needed to represent and IPV6 value
    
    See Also:
    
    Constant Field Values
  - IPV6_MAX_CHAR_BETWEEN_SEPARATOR
```
private static final int IPV6_MAX_CHAR_BETWEEN_SEPARATOR
```
    Maximum amount of value adding characters in between IPV6 separators
    
    See Also:
    
    Constant Field Values
  - IPV6_MIN_SEPARATORS
```
private static final int IPV6_MIN_SEPARATORS
```
    Minimum number of separators that must be present in an IPv6 string
    
    See Also:
    
    Constant Field Values
  - IPV6_MAX_SEPARATORS
```
private static final int IPV6_MAX_SEPARATORS
```
    Maximum number of separators that must be present in an IPv6 string
    
    See Also:
    
    Constant Field Values
  - IPV4_BYTE_COUNT
```
private static final int IPV4_BYTE_COUNT
```
    Number of bytes needed to represent and IPV4 value
    
    See Also:
    
    Constant Field Values
  - IPV4_MAX_CHAR_BETWEEN_SEPARATOR
```
private static final int IPV4_MAX_CHAR_BETWEEN_SEPARATOR
```
    Maximum amount of value adding characters in between IPV4 separators
    
    See Also:
    
    Constant Field Values
  - IPV4_SEPARATORS
```
private static final int IPV4_SEPARATORS
```
    Number of separators that must be present in an IPv4 string
    
    See Also:
    
    Constant Field Values
  - IPV4_PREFERRED
```
private static final boolean IPV4_PREFERRED
```
    true if ipv4 should be used on a system that supports ipv4 and ipv6.
  - logger
```
private static final InternalLogger logger
```
    The logger being used by this class
- Constructor Detail
  - NetUtil
```
private NetUtil()
```
    A constructor to stop this class being constructed.
- Method Detail
  - isIpV4StackPreferred
```
public static boolean isIpV4StackPreferred()
```
    Returns true if ipv4 should be prefered on a system that supports ipv4 and ipv6.
  - createByteArrayFromIpAddressString
```
public static byte[] createByteArrayFromIpAddressString(java.lang.String ipAddressString)
```
    Creates an byte[] based on an ipAddressString. No error handling is performed here.
  - convertToBytes
```
private static void convertToBytes(java.lang.String hexWord,
                                   byte[] ipByteArray,
                                   int byteIndex)
```
    Converts a 4 character hex word into a 2 byte word equivalent
  - getIntValue
```
static int getIntValue(char c)
```
  - isValidIpV6Address
```
public static boolean isValidIpV6Address(java.lang.String ipAddress)
```
  - isValidIp4Word
```
@Deprecated
public static boolean isValidIp4Word(java.lang.String word)
```
    Deprecated. Do not use; published by mistake.
  - isValidHexChar
```
private static boolean isValidHexChar(char c)
```
  - isValidNumericChar
```
private static boolean isValidNumericChar(char c)
```
  - isValidIpV4Address
```
public static boolean isValidIpV4Address(java.lang.String value)
```
    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 java.net.Inet6Address getByName(java.lang.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 java.net.Inet6Address getByName(java.lang.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 Don't turn IPv4 addressed to mapped addresses
    Returns:
    
    Inet6Address representation of the ip or null if not a valid IP address.
  - toAddressString
```
public static java.lang.String toAddressString(java.net.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 java.lang.String toAddressString(java.net.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
  - inRangeEndExclusive
```
private static boolean inRangeEndExclusive(int value,
                                           int start,
                                           int end)
```
    Does a range check on value if is within start (inclusive) and end (exclusive).
    Parameters:
    
    value - The value to checked if is within start (inclusive) and end (exclusive)
    
    start - The start of the range (inclusive)
    
    end - The end of the range (exclusive)
    
    Returns:
    true if value if is within start (inclusive) and end (exclusive)
    
    false otherwise

Class NetUtil

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOCALHOST4

LOCALHOST6

LOCALHOST

LOOPBACK_IF

SOMAXCONN

IPV6_WORD_COUNT

IPV6_MAX_CHAR_COUNT

IPV6_BYTE_COUNT

IPV6_MAX_CHAR_BETWEEN_SEPARATOR

IPV6_MIN_SEPARATORS

IPV6_MAX_SEPARATORS

IPV4_BYTE_COUNT

IPV4_MAX_CHAR_BETWEEN_SEPARATOR

IPV4_SEPARATORS

IPV4_PREFERRED

logger

Constructor Detail

NetUtil

Method Detail

isIpV4StackPreferred

createByteArrayFromIpAddressString

convertToBytes

getIntValue

isValidIpV6Address

isValidIp4Word

isValidHexChar

isValidNumericChar

isValidIpV4Address

getByName

getByName

toAddressString

toAddressString

inRangeEndExclusive