QDns(3qt)QDns(3qt)NAME
QDns - Asynchronous DNS lookups
#include <qdns.h>
Inherits QObject.
Public Members
enum RecordType { None, A, Aaaa, Mx, Srv, Cname, Ptr, Txt
}
QDns ()
QDns ( const QString & label, RecordType rr = A )
QDns ( const QHostAddress & address, RecordType rr = Ptr )
virtual ~QDns ()
virtual void setLabel ( const QString & label )
virtual void setLabel ( const QHostAddress & address )
QString label () const
virtual void setRecordType ( RecordType rr = A )
RecordType recordType () const
bool isWorking () const
QValueList<QHostAddress> addresses () const
QValueList<MailServer> mailServers () const
QValueList<Server> servers () const
QStringList hostNames () const
QStringList texts () const
QString canonicalName () const
QStringList qualifiedNames () const
Signals
void resultsReady ()
DESCRIPTION
The QDns class provides asynchronous DNS lookups.
Both Windows and UNIX provides synchronous DNS lookups;
Windows provides some asynchronous support too. Neither OS
provides asynchronous support for anything other than
hostname-to-address mapping.
QDns rectifies that, by providing asynchronous caching
lookups for the record types that we expect modern GUI
applications to need in the near future.
The class is a bit hard to use (although much simpler than
the native APIs); QSocket provides much simpler TCP
connection facilities. The aim of QDns is to provide a
correct and small API to the DNS: Nothing more.
(Correctness implies that the DNS information is correctly
cached, and correctly timed out.)
The API is made up of a constructor, functions to set the
DNS node (the domain in DNS terminology) and record type
(setLabel() and setRecordType()), the corresponding
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getters, an isWorking() function to determine whether QDns
is working or reading, a resultsReady() signal, and
finally query functions for the result.
There is one query function for each RecordType, namely
addresses(), mailServers(), servers(), hostNames() and
texts(). There are also two generic query functions:
canonicalName() return the name you'll presumably end up
using (the exact meaning of that depends on the record
type) and qualifiedNames() returns a list of the fully
qualified names label() maps to.
See also QSocket.
Member Type Documentation
QDns::RecordType
This enum type defines the record types QDns can handle.
The DNS provides many more; these are the ones we've
judged to be in current use, useful for GUI programs and
important enough to support right away:
None - no information. This exists only so that QDns can
have a default.
A - IPv4 addresses. By far the most common type.
Aaaa - Ipv6 addresses. So far mostly unused.
Mx - Mail eXchanger names. Used for mail delivery.
Srv - SeRVer names. Generic record type for finding
servers. So far mostly unused.
Cname - canonical name. Maps from nicknames to the true
name (the canonical name) for a host.
Ptr - name PoinTeR. Maps from IPv4 or IPv6 addresses to
hostnames.
Txt - arbitrary text for domains.
We expect that some support for the RFC-2535 extensions
will be added in future versions.
MEMBER FUNCTION DOCUMENTATIONQDns::QDns ()
Constructs a DNS query object with invalid settings both
for the label and the search type.
QDns::QDns ( const QHostAddress & address, QDns::RecordType rr =
Ptr )
Constructs a DNS query object that will return rr
information about address. The label is set to the IN-
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ADDR.ARPA domain name. This is useful in combination with
the Ptr record type (i.e. if you want to look up a
hostname for a given address).
The DNS lookup is started the next time the application
enters the event loop. When the result is found the signal
resultsReady() is emmitted.
rr defaults to Ptr, that maps addresses to hostnames.
QDns::QDns ( const QString & label, QDns::RecordType rr = A )
Constructs a DNS query object that will return rr
information about label.
The DNS lookup is started the next time the application
enters the event loop. When the result is found the signal
resultsReady() is emmitted.
rr defaults to A, IPv4 addresses.
QDns::~QDns () [virtual]
Destroys the query object and frees its allocated
resources.
QValueList<;QHostAddress> QDns::addresses () const
Returns a list of the addresses for this name if this QDns
object has a recordType() of QDns::A or QDns::Aaaa and the
answer is available, or an empty list else.
As a special case, if label() is a valid numeric IP
address, this function returns that address.
QString QDns::canonicalName () const
Returns the canonical name for this DNS node. (This works
regardless of what recordType() is set to.)
If the canonical name isn't known, this function returns a
null string.
The canonical name of a DNS node is its full name, or the
full name of the target of its CNAME. For example, if
l.trolltech.com is a CNAME to lupinella.troll.no, and the
search path for QDns is "trolltech.com", then the
canonical name for all of "lupinella", "l",
"lupinella.troll.no." and "l.trolltech.com" is
"lupinella.troll.no.".
QStringList QDns::hostNames () const
Returns a list of host names if the record type is Ptr.
bool QDns::isWorking () const
Returns TRUE if QDns is doing a lookup for this object,
and FALSE if this object has the information it wants.
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QDns emits the resultsReady() signal when the status
changes to FALSE.
QString QDns::label () const
Returns the domain name for which this object returns
information.
See also setLabel().
QValueList<;MailServer> QDns::mailServers () const
Returns a list of mail servers if the record type is Mx.
The struct QDns::MailServer contains the following
variables:
QString QDns::MailServer::name
Q_UINT16 QDns::MailServer::priority
QStringList QDns::qualifiedNames () const
Returns a list of the fully qualified names label() maps
to.
QDns::RecordType QDns::recordType() const
Returns the record type of this query object.
See also setRecordType() and RecordType.
void QDns::resultsReady () [signal]
This signal is emitted when results are available for one
of the qualifiedNames().
QValueList<;Server> QDns::servers () const
Returns a list of servers if the record type is Srv. The
struct QDns::Server contains the following variables:
QString QDns::Server::name
Q_UINT16 QDns::Server::priority
Q_UINT16 QDns::Server::weight
Q_UINT16 QDns::Server::port
void QDns::setLabel ( const QHostAddress & address ) [virtual]
Sets this query object to query for information about the
address address. The label is set to the IN-ADDR.ARPA
domain name. This is useful in combination with the Ptr
record type (i.e. if you want to look up a hostname for a
given address.
This does not change the recordType(), but its isWorking()
most likely changes as a result.
The DNS lookup is started the next time the application
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enters the event loop. When the result is found the signal
resultsReady() is emmitted.
void QDns::setLabel ( const QString & label ) [virtual]
Sets this query object to query for information about
label.
This does not change the recordType(), but its isWorking()
most likely changes as a result.
The DNS lookup is started the next time the application
enters the event loop. When the result is found the signal
resultsReady() is emmitted.
void QDns::setRecordType ( RecordType rr = A )
Sets this object to query for rr records.
The DNS lookup is started the next time the application
enters the event loop. When the result is found the signal
resultsReady() is emmitted.
See also RecordType.
QStringList QDns::texts () const
Returns a list of texts if the record type is Txt.
SEE ALSO
http://doc.trolltech.com/qdns.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page (qdns.3qt) and
the Qt version (2.3.1).
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