Qt 5.6 | Qt Network | C++ Classes | QHostAddress

Qt 5.6.2 Reference Documentation

# QHostAddress Class

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

Header: | #include <QHostAddress>
qmake: | QT += network

- List of all members, including inherited members

## Public Types

enum | SpecialAddress { Null, LocalHost, LocalHostIPv6, Broadcast, ..., Any }

## Public Functions

| QHostAddress()
| QHostAddress(quint32 ip4Addr)
| QHostAddress(quint8 *ip6Addr)
| QHostAddress(const 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 | isInSubnet(const QHostAddress &subnet, int netmask) const
bool | isInSubnet(const QPair<QHostAddress, int> &subnet) const
bool | isLoopback() const
bool | isMulticast() const
bool | isNull() const
QAbstractSocket::NetworkLayerProtocol | protocol() const
QString | scopeId() const
void | setAddress(quint32 ip4Addr)
void | setAddress(quint8 *ip6Addr)
void | setAddress(const quint8 *ip6Addr)
void | setAddress(const Q_IPV6ADDR &ip6Addr)
void | setAddress(const sockaddr *sockaddr)
bool | setAddress(const QString &address)
void | setScopeId(const QString &id)
void | swap(QHostAddress &other)
quint32 | toIPv4Address() const
quint32 | toIPv4Address(bool *ok) const
Q_IPV6ADDR | toIPv6Address() const
QString | toString() const
bool | operator!=(const QHostAddress &other) const
bool | operator!=(SpecialAddress other) const
QHostAddress & | operator=(QHostAddress &&other)
QHostAddress & | operator=(const QHostAddress &address)
QHostAddress & | operator=(const QString &address)
bool | operator==(const QHostAddress &other) const
bool | operator==(SpecialAddress other) const

## Static Public Members

QPair<QHostAddress, int> | parseSubnet(const QString &subnet)

## Related Non-Members

QDataStream & | operator<<(QDataStream &out, const QHostAddress &address)
QDataStream & | operator>>(QDataStream &in, QHostAddress &address)

## 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(), and retrieved with toIPv4Address(), toIPv6Address(), or toString(). You can check the type with protocol().

Note: Please note that QHostAddress does not do DNS lookups. QHostInfo is needed for that.

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

See also QHostInfo, 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::AnyIPv4` | `6` | The IPv4 any-address. Equivalent to QHostAddress("0.0.0.0"). A socket bound with this address will listen only on IPv4 interaces.
`QHostAddress::AnyIPv6` | `5` | The IPv6 any-address. Equivalent to QHostAddress("::"). A socket bound with this address will listen only on IPv6 interaces.
`QHostAddress::Any` | `4` | The dual stack any-address. A socket bound with this address will listen on both IPv4 and IPv6 interfaces.

## Member Function Documentation

### QHostAddress::QHostAddress()

Constructs a null host address object, i.e. an address which is not valid for any host or interface.

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 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).

This function was introduced in Qt 5.5.

### 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::isInSubnet(const QHostAddress &subnet, int netmask) const

Returns `true` if this IP is in the subnet described by the network prefix subnet and netmask netmask.

An IP is considered to belong to a subnet if it is contained between the lowest and the highest address in that subnet. In the case of IP version 4, the lowest address is the network address, while the highest address is the broadcast address.

The subnet argument does not have to be the actual network address (the lowest address in the subnet). It can be any valid IP belonging to that subnet. In particular, if it is equal to the IP address held by this object, this function will always return true (provided the netmask is a valid value).

This function was introduced in Qt 4.5.

See also parseSubnet().

### bool QHostAddress::isInSubnet(const QPair<QHostAddress, int> &subnet) const

This is an overloaded function.

Returns `true` if this IP is in the subnet described by subnet. The QHostAddress member of subnet contains the network prefix and the int (second) member contains the netmask (prefix length).

This function was introduced in Qt 4.5.

### bool QHostAddress::isLoopback() const

returns `true` if the address is the IPv6 loopback address, or any of the IPv4 loopback addresses.

This function was introduced in Qt 5.0.

### bool QHostAddress::isMulticast() const

Returns `true` if the address is an IPv4 or IPv6 multicast address, `false` otherwise.

This function was introduced in Qt 5.6.

### 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.

### `[static]` QPair<QHostAddress, int> QHostAddress::parseSubnet(const QString &subnet)

Parses the IP and subnet information contained in subnet and returns the network prefix for that network and its prefix length.

The IP address and the netmask must be separated by a slash (/).

This function supports arguments in the form:

- 123.123.123.123/n where n is any value between 0 and 32
- 123.123.123.123/255.255.255.255
- <ipv6-address>/n where n is any value between 0 and 128

For IP version 4, this function accepts as well missing trailing components (i.e., less than 4 octets, like "192.168.1"), followed or not by a dot. If the netmask is also missing in that case, it is set to the number of octets actually passed (in the example above, it would be 24, for 3 octets).

This function was introduced in Qt 4.5.

See also isInSubnet().

### 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.
- 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(), QNetworkInterface, and QNetworkInterface::interfaceFromName.

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

Set the IPv4 address specified by ip4Addr.

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

This is an overloaded function.

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 quint8 *ip6Addr)

This is an overloaded function.

Set the IPv6 address specified by ip6Addr.

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

This function was introduced in Qt 5.5.

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

This is an overloaded function.

Set the IPv6 address specified by ip6Addr.

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

This is an overloaded function.

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`.

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

This is an overloaded function.

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::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. The scope ID may be set as an interface name (such as "eth0" or "en1") or as an integer representing the interface index. If id is an interface name, QtNetwork will convert to an interface index using QNetworkInterface::interfaceIndexFromName() before calling the operating system networking functions.

This function was introduced in Qt 4.1.

See also scopeId(), QNetworkInterface, and QNetworkInterface::interfaceFromName.

### void QHostAddress::swap(QHostAddress &other)

### 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 valid if the protocol() is IPv4Protocol, or if the protocol is IPv6Protocol, and the IPv6 address is an IPv4 mapped address. (RFC4291)

See also toString().

### quint32 QHostAddress::toIPv4Address(bool *ok) 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 valid if the protocol() is IPv4Protocol, or if the protocol is IPv6Protocol, and the IPv6 address is an IPv4 mapped address. (RFC4291). In those cases, ok will be set to true. Otherwise, it will be set to false.

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.toIPv6Address();
      // addr contains 16 unsigned characters

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

This value is valid if the protocol() is IPv6Protocol. If the protocol is IPv4Protocol, then the address is returned an an IPv4 mapped IPv6 address. (RFC4291)

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". For IPv6 the string format will follow the RFC5952 recommendation. For QHostAddress::Any, its IPv4 address will be returned ("0.0.0.0")

See also toIPv4Address().

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

Returns `true` if this host address is not the same as the other address given; otherwise returns `false`.

This function was introduced in Qt 4.2.

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

Returns `true` if this host address is not the same as the other address given; otherwise returns `false`.

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

Move-assignment operator.

### 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)

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

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

## Related Non-Members

### QDataStream &operator<<(QDataStream &out, const QHostAddress &address)

Writes host address address to the stream out and returns a reference to the stream.

See also Serializing Qt Data Types.

### QDataStream &operator>>(QDataStream &in, QHostAddress &address)

Reads a host address into address from the stream in and returns a reference to the stream.

See also Serializing Qt Data Types.