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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QDns Class Reference<br><small>[<a href="network.html">network module</a>]</small></h1>
<p>The QDns class provides asynchronous DNS lookups.
<a href="#details">More...</a>
<p><tt>#include <<a href="qdns-h.html">qdns.h</a>></tt>
<p>Inherits <a href="qobject.html">QObject</a>.
<p><a href="qdns-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li class=fn>enum <a href="#RecordType-enum"><b>RecordType</b></a> { None, A, Aaaa, Mx, Srv, Cname, Ptr, Txt }</li>
<li class=fn><a href="#QDns"><b>QDns</b></a> ()</li>
<li class=fn><a href="#QDns-2"><b>QDns</b></a> ( const QString & label, RecordType rr = A )</li>
<li class=fn><a href="#QDns-3"><b>QDns</b></a> ( const QHostAddress & address, RecordType rr = Ptr )</li>
<li class=fn>virtual <a href="#~QDns"><b>~QDns</b></a> ()</li>
<li class=fn>virtual void <a href="#setLabel"><b>setLabel</b></a> ( const QString & label )</li>
<li class=fn>virtual void <a href="#setLabel-2"><b>setLabel</b></a> ( const QHostAddress & address )</li>
<li class=fn>QString <a href="#label"><b>label</b></a> () const</li>
<li class=fn>virtual void <a href="#setRecordType"><b>setRecordType</b></a> ( RecordType rr = A )</li>
<li class=fn>RecordType <a href="#recordType"><b>recordType</b></a> () const</li>
<li class=fn>bool <a href="#isWorking"><b>isWorking</b></a> () const</li>
<li class=fn>QValueList<QHostAddress> <a href="#addresses"><b>addresses</b></a> () const</li>
<li class=fn>QValueList<MailServer> <a href="#mailServers"><b>mailServers</b></a> () const</li>
<li class=fn>QValueList<Server> <a href="#servers"><b>servers</b></a> () const</li>
<li class=fn>QStringList <a href="#hostNames"><b>hostNames</b></a> () const</li>
<li class=fn>QStringList <a href="#texts"><b>texts</b></a> () const</li>
<li class=fn>QString <a href="#canonicalName"><b>canonicalName</b></a> () const</li>
<li class=fn>QStringList <a href="#qualifiedNames"><b>qualifiedNames</b></a> () const</li>
</ul>
<h2>Signals</h2>
<ul>
<li class=fn>void <a href="#resultsReady"><b>resultsReady</b></a> ()</li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
The QDns class provides asynchronous DNS lookups.
<p>
<p> 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.
<p> 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.
<p> The class is <em>not</em> straightforward to use (although it is much
simpler than the native APIs); <a href="qsocket.html">QSocket</a> 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.)
<p> The API comprises a constructor, functions to set the DNS node
(the domain in DNS terminology) and record type (<a href="#setLabel">setLabel</a>() and
<a href="#setRecordType">setRecordType</a>()), the corresponding get functions, an <a href="#isWorking">isWorking</a>()
function to determine whether QDns is working or reading, a
<a href="#resultsReady">resultsReady</a>() signal and query functions for the result.
<p> There is one query function for each RecordType, namely
<a href="#addresses">addresses</a>(), <a href="#mailServers">mailServers</a>(), <a href="#servers">servers</a>(), <a href="#hostNames">hostNames</a>() and <a href="#texts">texts</a>().
There are also two generic query functions: <a href="#canonicalName">canonicalName</a>()
returns the name you'll presumably end up using (the exact meaning
of this depends on the record type) and <a href="#qualifiedNames">qualifiedNames</a>() returns a
list of the fully qualified names <a href="#label">label</a>() maps to.
<p> <p>See also <a href="qsocket.html">QSocket</a> and <a href="io.html">Input/Output and Networking</a>.
<hr><h2>Member Type Documentation</h2>
<h3 class=fn><a name="RecordType-enum"></a>QDns::RecordType</h3>
<p> 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:
<ul>
<li><tt>QDns::None</tt> - No information. This exists only so that QDns can
have a default.
<li><tt>QDns::A</tt> - IPv4 addresses. By far the most common type.
<li><tt>QDns::Aaaa</tt> - IPv6 addresses. So far mostly unused.
<li><tt>QDns::Mx</tt> - Mail eXchanger names. Used for mail delivery.
<li><tt>QDns::Srv</tt> - SeRVer names. Generic record type for finding
servers. So far mostly unused.
<li><tt>QDns::Cname</tt> - Canonical names. Maps from nicknames to the true
name (the canonical name) for a host.
<li><tt>QDns::Ptr</tt> - name PoinTeRs. Maps from IPv4 or IPv6 addresses to hostnames.
<li><tt>QDns::Txt</tt> - arbitrary TeXT for domains.
</ul><p> We expect that some support for the
<a href="http://www.dns.net/dnsrd/rfc/rfc2535.html">RFC-2535</a>
extensions will be added in future versions.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QDns"></a>QDns::QDns ()
</h3>
Constructs a DNS query object with invalid settings for both the
label and the search type.
<h3 class=fn><a name="QDns-2"></a>QDns::QDns ( const <a href="qstring.html">QString</a> & label, <a href="qdns.html#RecordType-enum">RecordType</a> rr = A )
</h3>
Constructs a DNS query object that will return record type <em>rr</em>
information about <em>label</em>.
<p> The DNS lookup is started the next time the application enters the
event loop. When the result is found the signal <a href="#resultsReady">resultsReady</a>() is
emitted.
<p> <em>rr</em> defaults to <a href="#RecordType-enum">A</a>, IPv4 addresses.
<h3 class=fn><a name="QDns-3"></a>QDns::QDns ( const <a href="qhostaddress.html">QHostAddress</a> & address, <a href="qdns.html#RecordType-enum">RecordType</a> rr = Ptr )
</h3>
Constructs a DNS query object that will return record type <em>rr</em>
information about host address <em>address</em>. The label is set to the
IN-ADDR.ARPA domain name. This is useful in combination with the
<a href="#RecordType-enum">Ptr</a> record type (e.g. if you want to look up a hostname for a
given address).
<p> The DNS lookup is started the next time the application enters the
event loop. When the result is found the signal <a href="#resultsReady">resultsReady</a>() is
emitted.
<p> <em>rr</em> defaults to <a href="#RecordType-enum">Ptr</a>, that maps addresses to hostnames.
<h3 class=fn><a name="~QDns"></a>QDns::~QDns ()<tt> [virtual]</tt>
</h3>
Destroys the DNS query object and frees its allocated resources.
<h3 class=fn><a href="qvaluelist.html">QValueList</a><QHostAddress> <a name="addresses"></a>QDns::addresses () const
</h3>
Returns a list of the addresses for this name if this QDns object
has a <a href="#recordType">recordType</a>() of <a href="#RecordType-enum">QDns::A</a> or <a href="#RecordType-enum">QDns::Aaaa</a> and the answer
is available; otherwise returns an empty list.
<p> As a special case, if <a href="#label">label</a>() is a valid numeric IP address, this
function returns that address.
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qvaluelist.html">QValueList</a><QHostAddress> list = myDns.addresses();
QValueList<QHostAddress>::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
<p>
<h3 class=fn><a href="qstring.html">QString</a> <a name="canonicalName"></a>QDns::canonicalName () const
</h3>
Returns the canonical name for this DNS node. (This works
regardless of what <a href="#recordType">recordType</a>() is set to.)
<p> If the canonical name isn't known, this function returns a null
string.
<p> 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.".
<h3 class=fn><a href="qstringlist.html">QStringList</a> <a name="hostNames"></a>QDns::hostNames () const
</h3>
Returns a list of host names if the record type is <a href="#RecordType-enum">Ptr</a>.
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qstringlist.html">QStringList</a> list = myDns.hostNames();
QStringList::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
<p>
<h3 class=fn>bool <a name="isWorking"></a>QDns::isWorking () const
</h3>
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.
<p> QDns emits the <a href="#resultsReady">resultsReady</a>() signal when the status changes to FALSE.
<p>Example: <a href="mail-example.html#x705">network/mail/smtp.cpp</a>.
<h3 class=fn><a href="qstring.html">QString</a> <a name="label"></a>QDns::label () const
</h3>
<p> Returns the domain name for which this object returns information.
<p> <p>See also <a href="#setLabel">setLabel</a>().
<h3 class=fn><a href="qvaluelist.html">QValueList</a><MailServer> <a name="mailServers"></a>QDns::mailServers () const
</h3>
Returns a list of mail servers if the record type is <a href="#RecordType-enum">Mx</a>. The
class <tt>QDns::MailServer</tt> contains the following public variables:
<ul>
<li> <a href="qstring.html">QString</a> QDns::MailServer::name
<li> Q_UINT16 QDns::MailServer::priority
</ul>
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qvaluelist.html">QValueList</a><QDns::MailServer> list = myDns.mailServers();
QValueList<QDns::MailServer>::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
<p>
<p>Example: <a href="mail-example.html#x706">network/mail/smtp.cpp</a>.
<h3 class=fn><a href="qstringlist.html">QStringList</a> <a name="qualifiedNames"></a>QDns::qualifiedNames () const
</h3>
<p> Returns a list of the fully qualified names <a href="#label">label</a>() maps to.
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qstringlist.html">QStringList</a> list = myDns.qualifiedNames();
QStringList::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
<p>
<h3 class=fn><a href="qdns.html#RecordType-enum">RecordType</a> <a name="recordType"></a>QDns::recordType () const
</h3>
<p> Returns the record type of this DNS query object.
<p> <p>See also <a href="#setRecordType">setRecordType</a>() and <a href="#RecordType-enum">RecordType</a>.
<h3 class=fn>void <a name="resultsReady"></a>QDns::resultsReady ()<tt> [signal]</tt>
</h3>
<p> This signal is emitted when results are available for one of the
<a href="#qualifiedNames">qualifiedNames</a>().
<p>Example: <a href="mail-example.html#x707">network/mail/smtp.cpp</a>.
<h3 class=fn><a href="qvaluelist.html">QValueList</a><Server> <a name="servers"></a>QDns::servers () const
</h3>
Returns a list of servers if the record type is <a href="#RecordType-enum">Srv</a>. The class
<tt>QDns::Server</tt> contains the following public variables:
<ul>
<li> <a href="qstring.html">QString</a> QDns::Server::name
<li> Q_UINT16 QDns::Server::priority
<li> Q_UINT16 QDns::Server::weight
<li> Q_UINT16 QDns::Server::port
</ul>
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qvaluelist.html">QValueList</a><QDns::Server> list = myDns.servers();
QValueList<QDns::Server>::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
<h3 class=fn>void <a name="setLabel"></a>QDns::setLabel ( const <a href="qstring.html">QString</a> & label )<tt> [virtual]</tt>
</h3>
Sets this DNS query object to query for information about <em>label</em>.
<p> This does not change the <a href="#recordType">recordType</a>(), but its <a href="#isWorking">isWorking</a>() status
will probably change as a result.
<p> The DNS lookup is started the next time the application enters the
event loop. When the result is found the signal <a href="#resultsReady">resultsReady</a>() is
emitted.
<h3 class=fn>void <a name="setLabel-2"></a>QDns::setLabel ( const <a href="qhostaddress.html">QHostAddress</a> & address )<tt> [virtual]</tt>
</h3>
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
<p> Sets this DNS query object to query for information about the host
address <em>address</em>. The label is set to the IN-ADDR.ARPA domain
name. This is useful in combination with the <a href="#RecordType-enum">Ptr</a> record type
(e.g. if you want to look up a hostname for a given address).
<h3 class=fn>void <a name="setRecordType"></a>QDns::setRecordType ( <a href="qdns.html#RecordType-enum">RecordType</a> rr = A )<tt> [virtual]</tt>
</h3>
Sets this object to query for record type <em>rr</em> records.
<p> The DNS lookup is started the next time the application enters the
event loop. When the result is found the signal <a href="#resultsReady">resultsReady</a>() is
emitted.
<p> <p>See also <a href="#RecordType-enum">RecordType</a>.
<h3 class=fn><a href="qstringlist.html">QStringList</a> <a name="texts"></a>QDns::texts () const
</h3>
Returns a list of texts if the record type is <a href="#RecordType-enum">Txt</a>.
<p> Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
<pre>
<a href="qstringlist.html">QStringList</a> list = myDns.texts();
QStringList::Iterator it = list.<a href="qvaluelist.html#begin">begin</a>();
while( it != list.<a href="qvaluelist.html#end">end</a>() ) {
myProcessing( *it );
++it;
}
</pre>
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