QDnsLookup Class
The QDnsLookup class represents a DNS lookup. More...
| Header: | #include <QDnsLookup> |
| qmake: | QT += network |
| Since: | Qt 5.0 |
| Inherits: | QObject. |
Public Types
| enum | Error { NoError, ResolverError, OperationCancelledError, InvalidRequestError, ..., NotFoundError } |
| enum | Type { A, AAAA, ANY, CNAME, ..., TXT } |
Properties
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- 1 property inherited from QObject
Public Functions
| QDnsLookup(QObject * parent = 0) | |
| QDnsLookup(Type type, const QString & name, QObject * parent = 0) | |
| QDnsLookup(Type type, const QString & name, const QHostAddress & nameserver, QObject * parent = 0) | |
| ~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 |
| QList<QDnsDomainNameRecord> | nameServerRecords() const |
| QHostAddress | nameserver() 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 |
- 31 public functions inherited from QObject
Public Slots
- 1 public slot inherited from QObject
Signals
| void | finished() |
| void | nameChanged(const QString & name) |
| void | nameserverChanged(const QHostAddress & nameserver) |
| void | typeChanged(Type type) |
- 2 signals inherited from QObject
Additional Inherited Members
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. foreach (const QDnsServiceRecord &record, dns->serviceRecords()) { ... } 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 Type 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::ResolverError | 1 | there was an error initializing the system's DNS resolver. |
QDnsLookup::OperationCancelledError | 2 | the lookup was aborted using the abort() method. |
QDnsLookup::InvalidRequestError | 3 | the requested DNS lookup was invalid. |
QDnsLookup::InvalidReplyError | 4 | the reply returned by the server was invalid. |
QDnsLookup::ServerFailureError | 5 | the server encountered an internal failure while processing the request (SERVFAIL). |
QDnsLookup::ServerRefusedError | 6 | the 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. |
Property Documentation
error : const Error
This property holds the type of error that occurred if the DNS lookup failed, or NoError.
Access functions:
| Error | error() const |
Notifier signal:
| void | finished() |
errorString : const QString
This property holds a human-readable description of the error if the DNS lookup failed.
Access functions:
| QString | errorString() const |
Notifier signal:
| void | finished() |
name : QString
This property holds the name to lookup.
Note: The name will be encoded using IDNA, which means it's unsuitable for querying SRV records compatible with the DNS-SD specification.
Access functions:
| QString | name() const |
| void | setName(const QString & name) |
Notifier signal:
| void | nameChanged(const QString & name) |
nameserver : QHostAddress
This property holds the nameserver to use for DNS lookup.
Access functions:
| QHostAddress | nameserver() const |
| void | setNameserver(const QHostAddress & nameserver) |
Notifier signal:
| void | nameserverChanged(const QHostAddress & nameserver) |
type : Type
This property holds the type of DNS lookup.
Access functions:
| Type | type() const |
| void | setType(QDnsLookup::Type) |
Notifier signal:
| void | typeChanged(Type type) |
Member Function Documentation
QDnsLookup::QDnsLookup(QObject * parent = 0)
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 = 0)
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 = 0)
Constructs a QDnsLookup object for the given type, name and nameserver and sets parent as the parent object.
This function was introduced in Qt 5.4.
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.
[slot] void QDnsLookup::abort()
Aborts the DNS lookup operation.
If the lookup is already finished, does nothing.
QList<QDnsDomainNameRecord> QDnsLookup::canonicalNameRecords() const
Returns the list of canonical name records associated with this lookup.
QList<QDnsHostAddressRecord> QDnsLookup::hostAddressRecords() const
Returns the list of host address records associated with this lookup.
bool QDnsLookup::isFinished() const
Returns whether the reply has finished or was aborted.
[slot] void QDnsLookup::lookup()
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.
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.
The records are sorted according to RFC 2782, so if you use them to connect to servers, you should try them in the order they are listed.
QList<QDnsTextRecord> QDnsLookup::textRecords() const
Returns the list of text records associated with this lookup.
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