Dns Delphi DLL Reference Documentation

Dns

Current Version: 11.1.0

Requires Chilkat Bundle License

API for managing DNS nameservers to be used by Chilkat, and for doing DNS queries.

Create/Dispose

var
myObject: HCkDns;

begin
myObject := CkDns_Create();

// ...

CkDns_Dispose(myObject);
end;

function CkDns_Create: HCkDns; stdcall;

Creates an instance of the HCkDns object and returns a handle (i.e. a Pointer). The handle is passed in the 1st argument for the functions listed on this page.

procedure CkDns_Dispose(handle: HCkDns); stdcall;

Objects created by calling CkDns_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function.

Properties

DebugLogFilePath

procedure CkDns_getDebugLogFilePath(objHandle: HCkDns; outPropVal: HCkString); stdcall;
procedure CkDns_putDebugLogFilePath(objHandle: HCkDns; newPropVal: PWideChar); stdcall;
function CkDns__debugLogFilePath(objHandle: HCkDns): PWideChar; stdcall;

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

A timeout property set to 0, indicating an infinite timeout.
A hang occurring within an event callback in the application code.
An internal bug in the Chilkat code causing the hang.

See the notes about PWideChar memory ownership and validity.

More Information and Examples

Example showing how to use DebugLogFilePath.

HeartbeatMs

function CkDns_getHeartbeatMs(objHandle: HCkDns): Integer; stdcall;
procedure CkDns_putHeartbeatMs(objHandle: HCkDns; newPropVal: Integer); stdcall;

Introduced in version 9.5.0.96

The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.

More Information and Examples

Event Callback Examples

LastErrorHtml

procedure CkDns_getLastErrorHtml(objHandle: HCkDns; outPropVal: HCkString); stdcall;
function CkDns__lastErrorHtml(objHandle: HCkDns): PWideChar; stdcall;

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

See the notes about PWideChar memory ownership and validity.

LastErrorText

procedure CkDns_getLastErrorText(objHandle: HCkDns; outPropVal: HCkString); stdcall;
function CkDns__lastErrorText(objHandle: HCkDns): PWideChar; stdcall;

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

See the notes about PWideChar memory ownership and validity.

More Information and Examples

Concept of LastErrorText LastErrorText Standard Information

LastErrorXml

procedure CkDns_getLastErrorXml(objHandle: HCkDns; outPropVal: HCkString); stdcall;
function CkDns__lastErrorXml(objHandle: HCkDns): PWideChar; stdcall;

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

See the notes about PWideChar memory ownership and validity.

LastMethodSuccess

function CkDns_getLastMethodSuccess(objHandle: HCkDns): wordbool; stdcall;
procedure CkDns_putLastMethodSuccess(objHandle: HCkDns; newPropVal: wordbool); stdcall;

Indicates the success or failure of the most recent method call: True means success, False means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages.

MaxWaitMs

function CkDns_getMaxWaitMs(objHandle: HCkDns): Integer; stdcall;
procedure CkDns_putMaxWaitMs(objHandle: HCkDns; newPropVal: Integer); stdcall;

Introduced in version 9.5.0.96

The maxiumum number of milliseconds to wait for the answer to a DNS query. A value of 0 is to wait indefinitely (no timeout). It's not a good idea to specify 0 (infinite timeout) or a value less than 1000 (1 second). The default value is 10000 milliseconds.

NumNameservers

function CkDns_getNumNameservers(objHandle: HCkDns): Integer; stdcall;

Introduced in version 9.5.0.96

The number of nameservers currently being used by Chilkat for DNS queries in all objects/classes, such as for HTTP, Email, FTP, SSH, etc.

TlsPref

function CkDns_getTlsPref(objHandle: HCkDns): Integer; stdcall;
procedure CkDns_putTlsPref(objHandle: HCkDns; newPropVal: Integer); stdcall;

Introduced in version 9.5.0.96

Specifies the TLS preference. Possible values are:

0 = No TLS
1 = Prefer TLS if possible.
2 = Require TLS

The default value is 0. If TLS is preferred then DNS nameservers with TLS capability will be tried first. If none succeed, then UDP/TCP will be tried. If TLS is required, then only TLS capable nameservers will be tried and all DNS queries will use TLS.

Note: To use TLS, your application needs to first specify nameservers by calling AddNameserver once per nameserver with the supportsTls argument set to True.

VerboseLogging

function CkDns_getVerboseLogging(objHandle: HCkDns): wordbool; stdcall;
procedure CkDns_putVerboseLogging(objHandle: HCkDns; newPropVal: wordbool); stdcall;

If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

Version

procedure CkDns_getVersion(objHandle: HCkDns; outPropVal: HCkString); stdcall;
function CkDns__version(objHandle: HCkDns): PWideChar; stdcall;

Version of the component/library, such as "10.1.0"

See the notes about PWideChar memory ownership and validity.

More Information and Examples

How to get the Chilkat version at runtime.

Methods

AddDefaultNameservers

procedure CkDns_AddDefaultNameservers(objHandle: HCkDns) stdcall;

Introduced in version 9.5.0.96

Adds the default (auto-assigned) nameservers to the collection of nameservers used by Chilkat for DNS queries and domain to IP address lookups.

More Information and Examples

Use Public DNS Servers (Google and Cloudfare)Revert to Default DNS Nameservers

AddNameserver

procedure CkDns_AddNameserver(objHandle: HCkDns;
ipAddr: PWideChar;
supportsTls: wordbool) stdcall;

Introduced in version 9.5.0.96

Adds a new nameserver to the collection of nameservers used by Chilkat for DNS queries and domain to IP address lookups. The ipAddr specifies the IPv4 address of the nameserver. The supportsTls indicates if the namserver supports DoT (DNS over TLS. DoT uses port 853 for encrypted DNS communication.) If the TlsPreference property is set to 1 or 2, then Chilkat will use TLS nameservers.

More Information and Examples

Use Public DNS Servers (Google and Cloudfare)Revert to Default DNS Nameservers

GetNameserver

function CkDns_GetNameserver(objHandle: HCkDns;
    index: Integer;
    outStr: HCkString): wordbool; stdcall;
function CkDns__getNameserver(objHandle: HCkDns;
    index: Integer): PWideChar; stdcall;

Introduced in version 9.5.0.96

Returns the IP address of the Nth nameserver currently used by Chilkat for DNS queries and domain to IP address lookups. The index specifies the index of the nameserver. The 1st nameserver is at index 0.

Returns True for success, False for failure.

See the notes about PWideChar memory ownership and validity.

More Information and Examples

Revert to Default DNS Nameservers

Query

function CkDns_Query(objHandle: HCkDns;
    recordType: PWideChar;
    domain: PWideChar;
    answer: HCkJsonObject): wordbool; stdcall;

Introduced in version 9.5.0.96

Performs an DNS query for domain and returns the answer in answer. The type of DNS query is specified in recordType and can be A, AAAA, ALIAS, CAA, MX, NS, SOA, TXT. Additional record types can be added as needed.

More Information and Examples

DNS Query MX Records DNS Query TXT Records DNS Query AAAA Records DNS Query NS Records DNS Query SOA Records DNS Query CAA Records

QueryAsync ⁽¹⁾

function CkDns_QueryAsync(objHandle: HCkDns;
    recordType: PWideChar;
    domain: PWideChar;
    answer: HCkJsonObject): HCkTask; stdcall;

Introduced in version 9.5.0.96

Creates an asynchronous task to call the Query method with the arguments provided.

Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.

Returns nil on failure

RemoveAllNameservers

procedure CkDns_RemoveAllNameservers(objHandle: HCkDns) stdcall;

Introduced in version 9.5.0.96

Removes all nameservers from the collection of nameservers used by Chilkat. An application can call this method to reset to 0 nameservers before adding new nameservers. If a DNS domain to IP address resolution is needed by Chilkat, then the auto-assigned nameserver IP addresses will be automaticaly restored.

More Information and Examples

Use Public DNS Servers (Google and Cloudfare)Revert to Default DNS Nameservers

RemoveNameserver

procedure CkDns_RemoveNameserver(objHandle: HCkDns;
ipAddr: PWideChar) stdcall;

Introduced in version 9.5.0.96

Removes a nameserver from the collection of nameservers used by Chilkat. The ipAddr is the IPv4 address of the nameserver to be removed.

Events

AbortCheck

function MyAbortCheck(): Integer; cdecl;

Introduced in version 9.5.0.82

Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second. Return True to abort; return False to continue (not abort)

More Information and Examples

Chilkat Event Callback Examples

PercentDone

function MyPercentDone(pctDone: Integer): Integer; cdecl;

Introduced in version 9.5.0.82

This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).

The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.

Return True to abort; return False to continue (not abort)

More Information and Examples

Chilkat Event Callback Examples

ProgressInfo

procedure MyProgressInfo(name: PWideChar; value: PWideChar) cdecl;

Introduced in version 9.5.0.82

This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.

More Information and Examples

Chilkat Event Callback Examples

TaskCompleted

procedure MyTaskCompleted(task: HCkTask) cdecl;

Introduced in version 9.5.0.82

Called from the background thread when an asynchronous task completes.

More Information and Examples

Delphi DLL TaskCompleted Event Callback Example

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