- Qt 6.8
- Qt Network
- C++ Classes
- QNetworkInterface
- Qt 6.8.3 Reference Documentation

# QNetworkInterface Class

The QNetworkInterface class provides a listing of the host's IP addresses and network interfaces. More...

Header: | `#include <QNetworkInterface>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Network)` `target_link_libraries(mytarget PRIVATE Qt6::Network)`
qmake: | `QT += network`

- List of all members, including inherited members
- QNetworkInterface is part of Network Programming API and Implicitly Shared Classes.

Note: All functions in this class are reentrant.

## Public Types

enum | InterfaceFlag { IsUp, IsRunning, CanBroadcast, IsLoopBack, IsPointToPoint, CanMulticast }
flags | InterfaceFlags
enum | InterfaceType { Unknown, Loopback, Virtual, Ethernet, Wifi, …, Ieee1394 }

## Public Functions

| QNetworkInterface()
| QNetworkInterface(const QNetworkInterface &other)
| ~QNetworkInterface()
QList<QNetworkAddressEntry> | addressEntries() const
QNetworkInterface::InterfaceFlags | flags() const
QString | hardwareAddress() const
QString | humanReadableName() const
int | index() const
bool | isValid() const
int | maximumTransmissionUnit() const
QString | name() const
void | swap(QNetworkInterface &other)
QNetworkInterface::InterfaceType | type() const
QNetworkInterface & | operator=(const QNetworkInterface &other)

## Static Public Members

QList<QHostAddress> | allAddresses()
QList<QNetworkInterface> | allInterfaces()
QNetworkInterface | interfaceFromIndex(int index)
QNetworkInterface | interfaceFromName(const QString &name)
int | interfaceIndexFromName(const QString &name)
QString | interfaceNameFromIndex(int index)

## Related Non-Members

QDebug | operator<<(QDebug debug, const QNetworkInterface &networkInterface)

## Detailed Description

QNetworkInterface represents one network interface attached to the host where the program is being run. Each network interface may contain zero or more IP addresses, each of which is optionally associated with a netmask and/or a broadcast address. The list of such trios can be obtained with addressEntries(). Alternatively, when the netmask or the broadcast addresses or other information aren't necessary, use the allAddresses() convenience function to obtain just the IP addresses of the active interfaces.

QNetworkInterface also reports the interface's hardware address with hardwareAddress().

Not all operating systems support reporting all features. Only the IPv4 addresses are guaranteed to be listed by this class in all platforms. In particular, IPv6 address listing is only supported on Windows, Linux, macOS and the BSDs.

See also QNetworkAddressEntry.

## Member Type Documentation

### enum QNetworkInterface::InterfaceFlag
flags QNetworkInterface::InterfaceFlags

Specifies the flags associated with this network interface. The possible values are:

Constant | Value | Description
--- | --- | ---
`QNetworkInterface::IsUp` | `0x1` | the network interface is "up" - enabled by administrative action
`QNetworkInterface::IsRunning` | `0x2` | the network interface is operational: configured "up" and (typically) physically connected to a network
`QNetworkInterface::CanBroadcast` | `0x4` | the network interface works in broadcast mode
`QNetworkInterface::IsLoopBack` | `0x8` | the network interface is a loopback interface: that is, it's a virtual interface whose destination is the host computer itself
`QNetworkInterface::IsPointToPoint` | `0x10` | the network interface is a point-to-point interface: that is, there is one, single other address that can be directly reached by it.
`QNetworkInterface::CanMulticast` | `0x20` | the network interface supports multicasting

Note that one network interface cannot be both broadcast-based and point-to-point.

The InterfaceFlags type is a typedef for QFlags<InterfaceFlag>. It stores an OR combination of InterfaceFlag values.

### enum QNetworkInterface::InterfaceType

Specifies the type of hardware (PHY layer, OSI level 1) this interface is, if it could be determined. Interface types that are not among those listed below will generally be listed as Unknown, though future versions of Qt may add new enumeration values.

The possible values are:

Constant | Value | Description
--- | --- | ---
`QNetworkInterface::Unknown` | `0` | The interface type could not be determined or is not one of the other listed types.
`QNetworkInterface::Loopback` | `1` | The virtual loopback interface, which is assigned the loopback IP addresses (127.0.0.1, ::1).
`QNetworkInterface::Virtual` | `2` | A type of interface determined to be virtual, but not any of the other possible types. For example, tunnel interfaces are (currently) detected as virtual ones.
`QNetworkInterface::Ethernet` | `3` | IEEE 802.3 Ethernet interfaces, though on many systems other types of IEEE 802 interfaces may also be detected as Ethernet (especially Wi-Fi).
`QNetworkInterface::Wifi` | `8` | IEEE 802.11 Wi-Fi interfaces. Note that on some systems, QNetworkInterface may be unable to distinguish regular Ethernet from Wi-Fi and will not return this enum value.
`QNetworkInterface::Ieee80211` | `Wifi` | An alias for WiFi.
`QNetworkInterface::CanBus` | `5` | ISO 11898 Controller Area Network bus interfaces, usually found on automotive systems.
`QNetworkInterface::Fddi` | `7` | ANSI X3T12 Fiber Distributed Data Interface, a local area network over optical fibers.
`QNetworkInterface::Ppp` | `6` | Point-to-Point Protocol interfaces, establishing a direct connection between two nodes over a lower transport layer (often serial over radio or physical line).
`QNetworkInterface::Slip` | `4` | Serial Line Internet Protocol interfaces.
`QNetworkInterface::Phonet` | `9` | Interfaces using the Linux Phonet socket family, for communication with cellular modems. See the Linux kernel documentation for more information.
`QNetworkInterface::Ieee802154` | `10` | IEEE 802.15.4 Personal Area Network interfaces, other than 6LoWPAN (see below).
`QNetworkInterface::SixLoWPAN` | `11` | 6LoWPAN (IPv6 over Low-power Wireless Personal Area Networks) interfaces, which operate on IEEE 802.15.4 PHY, but have specific header compression schemes for IPv6 and UDP. This type of interface is often used for mesh networking.
`QNetworkInterface::Ieee80216` | `12` | IEEE 802.16 Wireless Metropolitan Area Network, also known under the commercial name "WiMAX".
`QNetworkInterface::Ieee1394` | `13` | IEEE 1394 interfaces (a.k.a. "FireWire").

## Member Function Documentation

### QNetworkInterface::QNetworkInterface()

Constructs an empty network interface object.

### QNetworkInterface::QNetworkInterface(const QNetworkInterface &other)

Creates a copy of the QNetworkInterface object contained in other.

### `[noexcept]` QNetworkInterface::~QNetworkInterface()

Frees the resources associated with the QNetworkInterface object.

### QList<QNetworkAddressEntry> QNetworkInterface::addressEntries() const

Returns the list of IP addresses that this interface possesses along with their associated netmasks and broadcast addresses.

If the netmask or broadcast address or other information is not necessary, you can call the allAddresses() function to obtain just the IP addresses of the active interfaces.

### `[static]` QList<QHostAddress> QNetworkInterface::allAddresses()

This convenience function returns all IP addresses found on the host machine. It is equivalent to calling addressEntries() on all the objects returned by allInterfaces() that are in the QNetworkInterface::IsUp state to obtain lists of QNetworkAddressEntry objects then calling QNetworkAddressEntry::ip() on each of these.

### `[static]` QList<QNetworkInterface> QNetworkInterface::allInterfaces()

Returns a listing of all the network interfaces found on the host machine. In case of failure it returns a list with zero elements.

### QNetworkInterface::InterfaceFlags QNetworkInterface::flags() const

Returns the flags associated with this network interface.

### QString QNetworkInterface::hardwareAddress() const

Returns the low-level hardware address for this interface. On Ethernet interfaces, this will be a MAC address in string representation, separated by colons.

Other interface types may have other types of hardware addresses. Implementations should not depend on this function returning a valid MAC address.

See also type().

### QString QNetworkInterface::humanReadableName() const

Returns the human-readable name of this network interface on Windows, such as "Local Area Connection", if the name could be determined. If it couldn't, this function returns the same as name(). The human-readable name is a name that the user can modify in the Windows Control Panel, so it may change during the execution of the program.

On Unix, this function currently always returns the same as name(), since Unix systems don't store a configuration for human-readable names.

### int QNetworkInterface::index() const

Returns the interface system index, if known. This is an integer assigned by the operating system to identify this interface and it generally doesn't change. It matches the scope ID field in IPv6 addresses.

If the index isn't known, this function returns 0.

### `[static]` QNetworkInterface QNetworkInterface::interfaceFromIndex(int index)

Returns a QNetworkInterface object for the interface whose internal ID is index. Network interfaces have a unique identifier called the "interface index" to distinguish it from other interfaces on the system. Often, this value is assigned progressively and interfaces being removed and then added again get a different value every time.

This index is also found in the IPv6 address' scope ID field.

### `[static]` QNetworkInterface QNetworkInterface::interfaceFromName(const QString &name)

Returns a QNetworkInterface object for the interface named name. If no such interface exists, this function returns an invalid QNetworkInterface object.

The string name may be either an actual interface name (such as "eth0" or "en1") or an interface index in string form ("1", "2", etc.).

See also name() and isValid().

### `[static]` int QNetworkInterface::interfaceIndexFromName(const QString &name)

Returns the index of the interface whose name is name or 0 if there is no interface with that name. This function should produce the same result as the following code, but will probably execute faster.

         QNetworkInterface::interfaceFromName(name).index()

See also interfaceFromName(), interfaceNameFromIndex(), and QNetworkDatagram::interfaceIndex().

### `[static]` QString QNetworkInterface::interfaceNameFromIndex(int index)

Returns the name of the interface whose index is index or an empty string if there is no interface with that index. This function should produce the same result as the following code, but will probably execute faster.

         QNetworkInterface::interfaceFromIndex(index).name()

See also interfaceFromIndex(), interfaceIndexFromName(), and QNetworkDatagram::interfaceIndex().

### bool QNetworkInterface::isValid() const

Returns `true` if this QNetworkInterface object contains valid information about a network interface.

### int QNetworkInterface::maximumTransmissionUnit() const

Returns the maximum transmission unit on this interface, if known, or 0 otherwise.

The maximum transmission unit is the largest packet that may be sent on this interface without incurring link-level fragmentation. Applications may use this value to calculate the size of the payload that will fit an unfragmented UDP datagram. Remember to subtract the sizes of headers used in your communication over the interface, e.g. TCP (20 bytes) or UDP (12), IPv4 (20) or IPv6 (40, absent some form of header compression), when computing how big a payload you can transmit. Also note that the MTU along the full path (the Path MTU) to the destination may be smaller than the interface's MTU.

See also QUdpSocket.

### QString QNetworkInterface::name() const

Returns the name of this network interface. On Unix systems, this is a string containing the type of the interface and optionally a sequence number, such as "eth0", "lo" or "pcn0". On Windows, it's an internal ID that cannot be changed by the user.

### `[noexcept]` void QNetworkInterface::swap(QNetworkInterface &other)

Swaps this network interface instance with other. This operation is very fast and never fails.

### QNetworkInterface::InterfaceType QNetworkInterface::type() const

Returns the type of this interface, if it could be determined. If it could not be determined, this function returns QNetworkInterface::Unknown.

See also hardwareAddress().

### QNetworkInterface &QNetworkInterface::operator=(const QNetworkInterface &other)

Copies the contents of the QNetworkInterface object contained in other into this one.

## Related Non-Members

### QDebug operator<<(QDebug debug, const QNetworkInterface &networkInterface)

Writes the QNetworkInterface networkInterface to the stream and returns a reference to the debug stream.