QHostInfo Class

The QHostInfo class provides host name lookup. More…

Header	`#include <QHostInfo>`
CMake	`target_link_libraries(app PRIVATE Nt::Network)`
Module	Nt Network C++ Classes

List of all members, including inherited members

Public Types

enum	HostInfoError

Public Functions

	QHostInfo(int lookupId = -1)
QString	hostName() const
void	setHostName(const QString &name)
QList<QHostAddress>	addresses() const
void	setAddresses(const QList<QHostAddress> &addresses)
HostInfoError	error() const
void	setError(HostInfoError error)
QString	errorString() const
void	setErrorString(const QString &errorString)
int	lookupId() const
void	setLookupId(int id)

Static Public Members

QHostInfo	fromName(const QString &name)
void	abortHostLookup(int lookupId)
QString	localHostName()
QString	localDomainName()
int	lookupHost(const QString &name, Func &&functor)
int	lookupHost(const QString &name, const QObject *context, Func &&functor)

Detailed Description

Call lookupHost() to resolve a name without blocking the event loop. The function you pass receives the result:

QHostInfo::lookupHost("example.com", [](const QHostInfo &info) {
    if (info.error() == QHostInfo::NoError)
        qDebug() << info.addresses().first().toString();
});

fromName() does the same lookup and blocks until it finishes.

See also QHostAddress.

Differences from Qt

There is no string-based SLOT() overload of lookupHost(). Each lookup uses its own thread rather than a shared pool, and abortHostLookup() only discards the result: the system resolver call itself runs to completion.

On Zephyr a lookup needs CONFIG_DNS_RESOLVER and runs in a thread with a stack of CONFIG_NT_THREAD_STACK_SIZE bytes; if that thread cannot be started, lookupHost() resolves the name before it returns. See Nt on Zephyr.

Member Type Documentation

enum QHostInfo::HostInfoError

Describes the outcome of a lookup.

Constant	Description
`QHostInfo::NoError`	The lookup succeeded.
`QHostInfo::HostNotFound`	No addresses were found for the name.
`QHostInfo::UnknownError`	Another error occurred.

Member Function Documentation

[explicit] QHostInfo::QHostInfo(int lookupId = -1)

Constructs an empty result with the lookup ID lookupId.

[static] void QHostInfo::abortHostLookup(int lookupId)

Discards the result of the lookup lookupId, if it has not been delivered.

See also lookupHost().

QList<QHostAddress> QHostInfo::addresses() const

Returns the addresses found for the host.

See also setAddresses().

HostInfoError QHostInfo::error() const

Returns the error of the lookup, or NoError if it succeeded.

See also errorString().

QString QHostInfo::errorString() const

Returns a description of the last error.

See also error().

[static] QHostInfo QHostInfo::fromName(const QString &name)

Looks up name and blocks until the result is known. An IP address is reverse-resolved; if that fails, its text is used as the host name.

See also lookupHost().

QString QHostInfo::hostName() const

Returns the name that was looked up.

See also setHostName().

[static] QString QHostInfo::localDomainName()

Returns this machine's DNS domain, or an empty string if it has none.

See also localHostName().

[static] QString QHostInfo::localHostName()

Returns this machine's host name.

See also localDomainName().

template <typename Func>[static] int QHostInfo::lookupHost(const QString &name, Func &&functor)

Looks up name on a background thread and calls functor with the result from the event loop. Returns the lookup's ID, which abortHostLookup() accepts.

See also fromName().

template <typename Func>[static] int QHostInfo::lookupHost(const QString &name, const QObject **context, Func &&functor*)

This is an overloaded function.

Looks up name and calls functor, unless context is destroyed first.

int QHostInfo::lookupId() const

Returns the ID of this lookup, or -1 if there is none.

See also setLookupId().

void QHostInfo::setAddresses(const QList<QHostAddress> &addresses)

Sets the list of found addresses to addresses.

See also addresses().

void QHostInfo::setError(HostInfoError error)

Sets the error to error.