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The QDns class provides asynchronous DNS lookups. More...
#include <qdns.h>
Inherits QObject.
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 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.
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:
We expect that some support for the RFC-2535 extensions will be added in future versions.
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.
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.
As a special case, if label() is a valid numeric IP address, this function returns that address.
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.".
QDns emits the resultsReady() signal when the status changes to FALSE.
Example: mail/smtp.cpp.
Returns the domain name for which this object returns information.
See also setLabel().
Example: mail/smtp.cpp.
Returns a list of the fully qualified names label() maps to.
Returns the record type of this query object.
See also setRecordType() and RecordType.
This signal is emitted when results are available for one of the qualifiedNames().
Example: mail/smtp.cpp.
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.
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 enters the event loop. When the result is found the signal resultsReady() is emmitted.
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.
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