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NAME

       QDns - Asynchronous DNS lookups

SYNOPSIS

       #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 provide synchronous DNS lookups; Windows provides some asynchronous
       support too. At the time of writing neither operating system provides asynchronous support
       for anything other than hostname-to-address mapping.

       QDns rectifies this shortcoming, by providing asynchronous caching lookups for the record
       types that we expect modern GUI applications to need in the near future.

       The class is not straightforward to use (although it is much simpler than the native
       APIs); QSocket provides much easier to use TCP connection facilities. The aim of QDns is
       to provide a correct and small API to the DNS and nothing more. (We use "correctness" to
       mean that the DNS information is correctly cached, and correctly timed out.)

       The API comprises a constructor, functions to set the DNS node (the domain in DNS
       terminology) and record type (setLabel() and setRecordType()), the corresponding get
       functions, an isWorking() function to determine whether QDns is working or reading, a
       resultsReady() signal and 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() returns the name you'll presumably end up using (the exact meaning of this
       depends on the record type) and qualifiedNames() returns a list of the fully qualified
       names label() maps to.

       See also QSocket and Input/Output and Networking.

   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:

       QDns::None - No information. This exists only so that QDns can have a default.

       QDns::A - IPv4 addresses. By far the most common type.

       QDns::Aaaa - IPv6 addresses. So far mostly unused.

       QDns::Mx - Mail eXchanger names. Used for mail delivery.

       QDns::Srv - SeRVer names. Generic record type for finding servers. So far mostly unused.

       QDns::Cname - Canonical names. Maps from nicknames to the true name (the canonical name)
       for a host.

       QDns::Ptr - name PoinTeRs. Maps from IPv4 or IPv6 addresses to hostnames.

       QDns::Txt - arbitrary TeXT for domains.

       We expect that some support for the RFC-2535 extensions will be added in future versions.

MEMBER FUNCTION DOCUMENTATION

QDns::QDns ()

       Constructs a DNS query object with invalid settings for both the label and the search
       type.

QDns::QDns ( const QString & label, RecordType rr = A )

       Constructs a DNS query object that will return record type 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 emitted.

       rr defaults to A, IPv4 addresses.

QDns::QDns ( const QHostAddress & address, RecordType rr = Ptr )

       Constructs a DNS query object that will return record type rr information about host
       address address. The label is set to the IN-ADDR.ARPA domain name. This is useful in
       combination with the Ptr record type (e.g. 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 emitted.

       rr defaults to Ptr, that maps addresses to hostnames.

QDns::~QDns () [virtual]

       Destroys the DNS 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; otherwise returns an empty list.

       As a special case, if label() is a valid numeric IP address, this function returns that
       address.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QValueList<QHostAddress> list = myDns.addresses();
           QValueList<QHostAddress>::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

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 lillian.troll.no, and the search path
       for QDns is" trolltech.com", then the canonical name for all of "lillian"," l",
       "lillian.troll.no." and "l.trolltech.com" is" lillian.troll.no.".

QStringList QDns::hostNames () const

       Returns a list of host names if the record type is Ptr.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QStringList list = myDns.hostNames();
           QStringList::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

bool QDns::isWorking () const

       Returns TRUE if QDns is doing a lookup for this object (i.e. if it does not already have
       the necessary information); otherwise returns FALSE.

       QDns emits the resultsReady() signal when the status changes to FALSE.

       Example: network/mail/smtp.cpp.

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 class QDns::MailServer
       contains the following public variables:

       QString QDns::MailServer::name

       Q_UINT16 QDns::MailServer::priority

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QValueList<QDns::MailServer> list = myDns.mailServers();
           QValueList<QDns::MailServer>::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

       Example: network/mail/smtp.cpp.

QStringList QDns::qualifiedNames () const

       Returns a list of the fully qualified names label() maps to.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QStringList list = myDns.qualifiedNames();
           QStringList::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

RecordType QDns::recordType () const

       Returns the record type of this DNS query object.

       See also setRecordType() and RecordType.

void QDns::resultsReady () [signal]

       This signal is emitted when results are available for one of the qualifiedNames().

       Example: network/mail/smtp.cpp.

QValueList<Server> QDns::servers () const

       Returns a list of servers if the record type is Srv. The class QDns::Server contains the
       following public variables:

       QString QDns::Server::name

       Q_UINT16 QDns::Server::priority

       Q_UINT16 QDns::Server::weight

       Q_UINT16 QDns::Server::port

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QValueList<QDns::Server> list = myDns.servers();
           QValueList<QDns::Server>::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

void QDns::setLabel ( const QString & label ) [virtual]

       Sets this DNS query object to query for information about label.

       This does not change the recordType(), but its isWorking() status will probably change 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 emitted.

void QDns::setLabel ( const QHostAddress & address ) [virtual]

       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Sets this DNS query object to query for information about the host address address. The
       label is set to the IN-ADDR.ARPA domain name. This is useful in combination with the Ptr
       record type (e.g. if you want to look up a hostname for a given address).

void QDns::setRecordType ( RecordType rr = A ) [virtual]

       Sets this object to query for record type 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 emitted.

       See also RecordType.

QStringList QDns::texts () const

       Returns a list of texts if the record type is Txt.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

           QStringList list = myDns.texts();
           QStringList::Iterator it = list.begin();
           while( it != list.end() ) {
               myProcessing( *it );
               ++it;
           }

SEE ALSO

       http://doc.trolltech.com/qdns.html http://www.trolltech.com/faq/tech.html

COPYRIGHT

       Copyright 1992-2007 Trolltech ASA, 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 help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
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       If you find errors in 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 (3.3.8).