The QDnsLookup class represents a DNS lookup. More...

Inheritance diagram for QDnsLookup:

Public Types
enum	Error

enum	Type

Public Signals
void	finished ()

void	nameChanged (const QString &name)

void	nameserverChanged (const QHostAddress &nameserver)

void	typeChanged (Type type)

Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Slots
void	abort ()

void	lookup ()

Public Slots inherited from QObject
void	deleteLater ()

Public Methods
	QDnsLookup (QObject *parent=nullptr)

	QDnsLookup (Type type, const QString &name, const QHostAddress &nameserver, QObject *parent=nullptr)

	QDnsLookup (Type type, const QString &name, QObject *parent=nullptr)

	~QDnsLookup ()

QList< QDnsDomainNameRecord >	canonicalNameRecords () const

Error	error () const

QString	errorString () const

QList< QDnsHostAddressRecord >	hostAddressRecords () const

bool	isFinished () const

QList< QDnsMailExchangeRecord >	mailExchangeRecords () const

QString	name () const

QHostAddress	nameserver () const

QList< QDnsDomainNameRecord >	nameServerRecords () const

QList< QDnsDomainNameRecord >	pointerRecords () const

QList< QDnsServiceRecord >	serviceRecords () const

void	setName (const QString &name)

void	setNameserver (const QHostAddress &nameserver)

void	setType (QDnsLookup::Type)

QList< QDnsTextRecord >	textRecords () const

Type	type () const

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Properties
	error

	errorString

	name

	nameserver

	type

Properties inherited from QObject
	objectName

Additional Inherited Members
Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QDnsLookup class represents a DNS lookup. QDnsLookup uses the mechanisms provided by the operating system to perform DNS lookups. To perform a lookup you need to specify a name and type then invoke the lookup() slot. The finished() signal will be emitted upon completion.

For example, you can determine which servers an XMPP chat client should connect to for a given domain with:

void MyObject::lookupServers()
{
    // Create a DNS lookup.
    dns = new QDnsLookup(this);
    connect(dns, SIGNAL(finished()), this, SLOT(handleServers()));
 
    // Find the XMPP servers for gmail.com
    dns->setType(QDnsLookup::SRV);
    dns->setName("_xmpp-client._tcp.gmail.com");
    dns->lookup();
}

Once the request finishes you can handle the results with:

   void MyObject::handleServers()
   {
      // Check the lookup succeeded.
      if (dns->error() != QDnsLookup::NoError) {
         qWarning("DNS lookup failed");
         dns->deleteLater();
         return;
      }
 
      // Handle the results.
      const auto records = dns->serviceRecords();
      for (const QDnsServiceRecord &record : records) {
         ...
      }
   }
   dns->deleteLater();
}

Note: If you simply want to find the IP address(es) associated with a host name, or the host name associated with an IP address you should use QHostInfo instead.

Member Enumeration Documentation

enum QDnsLookup::Error

Indicates all possible error conditions found during the processing of the DNS lookup.

Constant	Value	Description
`QDnsLookup::NoError`	`0`	no error condition
`QDnsLookup::`	`1`	there was an error initializing the system's DNS resolver
`QDnsLookup::ResolverError`	`2`	lookup was aborted using the abort() method
`QDnsLookup::OperationCancelledError`	`3`	requested DNS lookup was invalid
`QDnsLookup::InvalidRequestError`	`4`	requested DNS lookup was invalid
`QDnsLookup::InvalidReplyError`	`5`	reply returned by the server was invalid
`QDnsLookup::ServerRefusedError`	`7`	server refused to process the request for security or policy reasons (REFUSED)
`QDnsLookup::NotFoundError`	`7`	the requested domain name does not exist (NXDOMAIN)

enum QDnsLookup::Type

Indicates the type of DNS lookup that was performed.

Constant	Value	Description
`QDnsLookup::A`	`1`	IPv4 address records
`QDnsLookup::AAAA`	`28`	IPv6 address records
`QDnsLookup::ANY`	`255`	any records
`QDnsLookup::CNAME`	`5`	canonical name records
`QDnsLookup::MX`	`15`	mail exchange records
`QDnsLookup::NS`	`2`	name server records
`QDnsLookup::PTR`	`12`	pointer records
`QDnsLookup::SRV`	`33`	service records
`QDnsLookup::TXT`	`16`	text records

Constructor & Destructor Documentation

QDnsLookup::QDnsLookup ( QObject * parent = nullptr )

explicit

Constructs a QDnsLookup object and sets parent as the parent object. The type property will default to QDnsLookup::A.

QDnsLookup::QDnsLookup	(	Type	type,
		const QString &	name,
		QObject *	parent = `nullptr`
	)

Constructs a QDnsLookup object for the given type and name and sets parent as the parent object.

QDnsLookup::QDnsLookup	(	Type	type,
		const QString &	name,
		const QHostAddress &	nameserver,
		QObject *	parent = `nullptr`
	)

Constructs a QDnsLookup object for the given type, name and nameserver and sets parent as the parent object.

QDnsLookup::~QDnsLookup ( )

Destroys the QDnsLookup object.

It is safe to delete a QDnsLookup object even if it is not finished, you will simply never receive its results.

Method Documentation

void QDnsLookup::abort ( )

slot

Aborts the DNS lookup operation.

QList< QDnsDomainNameRecord > QDnsLookup::canonicalNameRecords ( ) const

Returns the list of canonical name records associated with this lookup.

Error QDnsLookup::error ( ) const

Returns the type of error which occurred.

QString QDnsLookup::errorString ( ) const

Returns a human readable description of the error which occurred.

void QDnsLookup::finished ( )

signal

This signal is emitted when the reply has finished processing.

QList< QDnsHostAddressRecord > QDnsLookup::hostAddressRecords ( ) const

Returns the list of host address records associated with this lookup.

bool QDnsLookup::isFinished ( ) const

Returns true if the DNS lookup has finished or failed.

void QDnsLookup::lookup ( )

slot

Performs the DNS lookup. The finished signal is emitted upon completion.

QList< QDnsMailExchangeRecord > QDnsLookup::mailExchangeRecords ( ) const

Returns the list of mail exchange records associated with this lookup.

The records are sorted according to RFC 5321 so if you use them to connect to servers, you should try them in the order they are listed.

QString QDnsLookup::name ( ) const

Returns the name of the DNS lookup.

void QDnsLookup::nameChanged ( const QString & name )

signal

This signal is emitted when the lookup name changes. The new lookup name is name.

QHostAddress QDnsLookup::nameserver ( ) const

Returns the nameserver which will be used for the DNS lookup.

void QDnsLookup::nameserverChanged ( const QHostAddress & nameserver )

signal

This signal is emitted when the nameserver changes.

QList< QDnsDomainNameRecord > QDnsLookup::nameServerRecords ( ) const

Returns the list of name server records associated with this lookup.

QList< QDnsDomainNameRecord > QDnsLookup::pointerRecords ( ) const

Returns the list of pointer records associated with this lookup.

QList< QDnsServiceRecord > QDnsLookup::serviceRecords ( ) const

Returns the list of service records associated with this lookup.

void QDnsLookup::setName ( const QString & name )

Sets the DNS lookup to name.

void QDnsLookup::setNameserver ( const QHostAddress & nameserver )

Sets the nameserver which will be used for the DNS lookup.

void QDnsLookup::setType ( QDnsLookup::Type )

Sets the type of DNS lookup to perform.

QList< QDnsTextRecord > QDnsLookup::textRecords ( ) const

Returns the list of text records associated with this DNS lookup.

Type QDnsLookup::type ( ) const

Returns the type of DNS lookup which will be performed.

void QDnsLookup::typeChanged ( Type type )

signal

This signal is emitted when the lookup type changes. The new lookup type is type.

Property Documentation

QDnsLookup::error

The type of error that occurred if the DNS lookup failed, or NoError.

Properties	Class Methods
read	error
notify	finished

QDnsLookup::errorString

A human readable description of the error if the DNS lookup failed.

Properties	Class Methods
read	errorString
notify	finished

QDnsLookup::name

The name to lookup.

The name will be encoded using IDNA, which means it is unsuitable for querying SRV records compatible with the DNS-SD specification.

Properties	Class Methods
read	name
write	setName
notify	nameChanged

QDnsLookup::nameserver

The nameserver to use for DNS lookup.

Properties	Class Methods
read	nameserver
write	setNameserver
notify	nameserverChanged

QDnsLookup::type

The type of DNS lookup.

Properties	Class Methods
read	type
write	setType
notify	typeChanged

Public Types

Public Signals

Public Slots

Public Methods

Properties

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Property Documentation