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# QHostAddress Class Reference
[QtNetwork module]

The QHostAddress class provides an IP address. More...

    #include <QHostAddress>

- List of all members, including inherited members
- Qt 3 support members

### Public Types

- enum SpecialAddress { Null, LocalHost, LocalHostIPv6, Broadcast, Any, AnyIPv6 }

### Public Functions

- QHostAddress ()
- QHostAddress ( quint32 ip4Addr )
- QHostAddress ( quint8 * ip6Addr )
- QHostAddress ( const Q_IPV6ADDR & ip6Addr )
- QHostAddress ( const sockaddr * sockaddr )
- QHostAddress ( const QString & address )
- QHostAddress ( const QHostAddress & address )
- QHostAddress ( SpecialAddress address )
- ~QHostAddress ()
- void clear ()
- bool isNull () const
- QAbstractSocket::NetworkLayerProtocol protocol () const
- QString scopeId () const
- void setAddress ( quint32 ip4Addr )
- void setAddress ( quint8 * ip6Addr )
- void setAddress ( const Q_IPV6ADDR & ip6Addr )
- bool setAddress ( const QString & address )
- void setAddress ( const sockaddr * sockaddr )
- void setScopeId ( const QString & id )
- quint32 toIPv4Address () const
- Q_IPV6ADDR toIPv6Address () const
- QString toString () const
- QHostAddress & operator= ( const QHostAddress & address )
- QHostAddress & operator= ( const QString & address )
- bool operator== ( const QHostAddress & other ) const
- bool operator== ( SpecialAddress other ) const

## Detailed Description

The QHostAddress class provides an IP address.

This class holds an IPv4 or IPv6 address in a platform- and protocol-independent manner.

QHostAddress is normally used with the QTcpSocket, QTcpServer, and QUdpSocket to connect to a host or to set up a server.

A host address is set with setAddress(), checked for its type using isIPv4Address() or isIPv6Address(), and retrieved with toIPv4Address(), toIPv6Address(), or toString().

The class also supports common predefined addresses: Null, LocalHost, LocalHostIPv6, Broadcast, and Any.

See also QTcpSocket, QTcpServer, and QUdpSocket.

## Member Type Documentation

### enum QHostAddress::SpecialAddress

Constant | Value | Description
--- | --- | ---
`QHostAddress::Null` | `0` | The null address object. Equivalent to QHostAddress().
`QHostAddress::LocalHost` | `2` | The IPv4 localhost address. Equivalent to QHostAddress("127.0.0.1").
`QHostAddress::LocalHostIPv6` | `3` | The IPv6 localhost address. Equivalent to QHostAddress("::1").
`QHostAddress::Broadcast` | `1` | The IPv4 broadcast address. Equivalent to QHostAddress("255.255.255.255").
`QHostAddress::Any` | `4` | The IPv4 any-address. Equivalent to QHostAddress("0.0.0.0").
`QHostAddress::AnyIPv6` | `5` | The IPv6 any-address. Equivalent to QHostAddress("::").

## Member Function Documentation

### QHostAddress::QHostAddress ()

Constructs a host address object with the IP address 0.0.0.0.

See also clear().

### QHostAddress::QHostAddress ( quint32 ip4Addr )

Constructs a host address object with the IPv4 address ip4Addr.

### QHostAddress::QHostAddress ( quint8 * ip6Addr )

Constructs a host address object with the IPv6 address ip6Addr.

ip6Addr must be a 16-byte array in network byte order (big endian).

### QHostAddress::QHostAddress ( const Q_IPV6ADDR & ip6Addr )

Constructs a host address object with the IPv6 address ip6Addr.

### QHostAddress::QHostAddress ( const sockaddr * sockaddr )

Constructs an IPv4 or IPv6 address using the address specified by the native structure sockaddr.

See also setAddress().

### QHostAddress::QHostAddress ( const QString & address )

Constructs an IPv4 or IPv6 address based on the string address (e.g., "127.0.0.1").

See also setAddress().

### QHostAddress::QHostAddress ( const QHostAddress & address )

Constructs a copy of the given address.

### QHostAddress::QHostAddress ( SpecialAddress address )

Constructs a QHostAddress object for address.

### QHostAddress::~QHostAddress ()

Destroys the host address object.

### void QHostAddress::clear ()

Sets the host address to 0.0.0.0.

### bool QHostAddress::isNull () const

Returns true if this host address is null (INADDR_ANY or in6addr_any). The default constructor creates a null address, and that address is not valid for any host or interface.

### QAbstractSocket::NetworkLayerProtocol QHostAddress::protocol () const

Returns the network layer protocol of the host address.

### QString QHostAddress::scopeId () const

Returns the scope ID of an IPv6 address. For IPv4 addresses, or if the address does not contain a scope ID, an empty QString is returned.

The IPv6 scope ID specifies the scope of reachability for non-global IPv6 addresses, limiting the area in which the address can be used. All IPv6 addresses are associated with such a reachability scope. The scope ID is used to disambiguate addresses that are not guaranteed to be globally unique.

IPv6 specifies the following four levels of reachability:

- Node-local: Addresses that are only used for communicating with services on the same interface (e.g., the loopback interface "::1").
- Link-local: Addresses that are local to the network interface (link). There is always one link-local address for each IPv6 interface on your host. Link-local addresses ("fe80...") are generated from the MAC address of the local network adaptor, and are not guaranteed to be unique.
- Site-local: Addresses that are local to the site / private network (e.g., the company intranet). Site-local addresses ("fec0...") are usually distributed by the site router, and are not guaranteed to be unique outside of the local site.
- Global: For globally routable addresses, such as public servers on the Internet.

When using a link-local or site-local address for IPv6 connections, you must specify the scope ID. The scope ID for a link-local address is usually the same as the interface name (e.g., "eth0", "en1") or number (e.g., "1", "2").

This function was introduced in Qt 4.1.

See also setScopeId().

### void QHostAddress::setAddress ( quint32 ip4Addr )

Set the IPv4 address specified by ip4Addr.

### void QHostAddress::setAddress ( quint8 * ip6Addr )

This is an overloaded member function, provided for convenience.

Set the IPv6 address specified by ip6Addr.

ip6Addr must be an array of 16 bytes in network byte order (high-order byte first).

### void QHostAddress::setAddress ( const Q_IPV6ADDR & ip6Addr )

This is an overloaded member function, provided for convenience.

Set the IPv6 address specified by ip6Addr.

### bool QHostAddress::setAddress ( const QString & address )

This is an overloaded member function, provided for convenience.

Sets the IPv4 or IPv6 address specified by the string representation specified by address (e.g. "127.0.0.1"). Returns true and sets the address if the address was successfully parsed; otherwise returns false.

### void QHostAddress::setAddress ( const sockaddr * sockaddr )

This is an overloaded member function, provided for convenience.

Sets the IPv4 or IPv6 address specified by the native structure sockaddr. Returns true and sets the address if the address was successfully parsed; otherwise returns false.

### void QHostAddress::setScopeId ( const QString & id )

Sets the IPv6 scope ID of the address to id. If the address protocol is not IPv6, this function does nothing.

This function was introduced in Qt 4.1.

See also scopeId().

### quint32 QHostAddress::toIPv4Address () const

Returns the IPv4 address as a number.

For example, if the address is 127.0.0.1, the returned value is 2130706433 (i.e. 0x7f000001).

This value is only valid if isIp4Addr() returns true.

See also toString().

### Q_IPV6ADDR QHostAddress::toIPv6Address () const

Returns the IPv6 address as a Q_IPV6ADDR structure. The structure consists of 16 unsigned characters.

        Q_IPV6ADDR addr = hostAddr.ip6Addr();
        // addr contains 16 unsigned characters

        for (int i = 0; i < 16; ++i) {
            // process addr[i]
        }

This value is only valid if isIPv6Address() returns true.

See also toString().

### QString QHostAddress::toString () const

Returns the address as a string.

For example, if the address is the IPv4 address 127.0.0.1, the returned string is "127.0.0.1".

See also toIPv4Address().

### QHostAddress & QHostAddress::operator= ( const QHostAddress & address )

Assigns another host address to this object, and returns a reference to this object.

### QHostAddress & QHostAddress::operator= ( const QString & address )

This is an overloaded member function, provided for convenience.

Assigns the host address address to this object, and returns a reference to this object.

See also setAddress().

### bool QHostAddress::operator== ( const QHostAddress & other ) const

Returns true if this host address is the same as the other address given; otherwise returns false.

### bool QHostAddress::operator== ( SpecialAddress other ) const

This is an overloaded member function, provided for convenience.

Returns true if this host address is the same as the other address given; otherwise returns false.