Q3Dns Class Reference
[Qt3Support module]

Detailed Description

The Q3Dns 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.

Q3Dns 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); Q3Socket provides much easier to use TCP connection facilities. The aim of Q3Dns 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 Q3Dns 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 Q3Socket.

Member Type Documentation

 Q3ValueList<QHostAddress> list = myDns.addresses();
 Q3ValueList<QHostAddress>::Iterator it = list.begin();
 while( it != list.end() ) {
     myProcessing( *it );
     ++it;
 }

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

 Q3ValueList<Q3Dns::MailServer> list = myDns.mailServers();
 Q3ValueList<Q3Dns::MailServer>::Iterator it = list.begin();
 while( it != list.end() ) {
     myProcessing( *it );
     ++it;
 }

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

 Q3ValueList<Q3Dns::Server> list = myDns.servers();
 Q3ValueList<Q3Dns::Server>::Iterator it = list.begin();
 while( it != list.end() ) {
     myProcessing( *it );
     ++it;
 }

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