The QDns class provides asynchronous DNS lookups. This class is part of the Qt Network Extension. 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() 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.
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.
Constructs a DNS query object with invalid settings both for the label and the search type.
Constructs a DNS query object that will return rr information about label.
rr defaults to A,
IPv4 addresses.
Destroys the query object and frees its allocated resources.
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.
Returns TRUE if QDns is doing a lookup for this object, and FALSE if this object has the information it wants.
QDns emits the resultsReady() signal when the status changes to FALSE.
Returns the domain name for which this object returns information.
See also: setLabel().
Returns the record type of this query object.
See also: setRecordType() and RecordType.
[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.
[virtual]
Sets this object to query for rr records.
See also: RecordType.
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