Dns Unicode C Reference Documentation

Dns

Current Version: 9.5.0.97

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

Create/Dispose

HCkDnsW instance = CkDnsW_Create();
// ...
CkDnsW_Dispose(instance);
HCkDnsW CkDnsW_Create(void);

Creates an instance of the HCkDnsW object and returns a handle ("void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.

void CkDnsW_Dispose(HCkDnsW handle);

Objects created by calling CkDnsW_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkDnsW_Dispose.

Callback Functions

Callback Functions introduced in Chilkat v9.5.0.56
void CkDnsW_setAbortCheck(HCkDnsW cHandle, BOOL (*fnAbortCheck)(void));

Provides the opportunity for a method call to be aborted. If TRUE is returned, the operation in progress is aborted. Return FALSE to allow the current method call to continue. This callback function is called periodically based on the value of the HeartbeatMs property. (If HeartbeatMs is 0, then no callbacks are made.) As an example, to make 5 AbortCheck callbacks per second, set the HeartbeatMs property equal to 200.

void CkDnsW_setPercentDone(HCkDnsW cHandle, BOOL (*fnPercentDone)(int pctDone));

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This callback is only called when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For methods that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

This callback counts as an AbortCheck callback, and takes the place of the AbortCheck event when it fires.

The return value indicates whether the method call should be aborted, or whether it should proceed. Return TRUE to abort, and FALSE to proceed.

void CkDnsW_setProgressInfo(HCkDnsW cHandle, void (*fnProgressInfo)(const wchar_t *name, const wchar_t *value));

This is a general callback that provides name/value information about what is happening at certain points during a method call. To see the information provided in ProgressInfo callbacks, if any, write code to handle this event and log the name/value pairs. Most are self-explanatory.

void CkDnsW_setTaskCompleted(HCkDnsW cHandle, void (*fnTaskCompleted)(HCkTaskW hTask));

Called in the background thread when an asynchronous task completes. (Note: When an async method is running, all callbacks are in the background thread.)

Properties

DebugLogFilePath
void CkDnsW_getDebugLogFilePath(HCkDnsW cHandle, HCkString retval);
void CkDnsW_putDebugLogFilePath(HCkDnsW cHandle, const wchar_t *newVal);
const wchar_t *CkDnsW_debugLogFilePath(HCkDnsW cHandle);

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

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HeartbeatMs
int CkDnsW_getHeartbeatMs(HCkDnsW cHandle);
void CkDnsW_putHeartbeatMs(HCkDnsW cHandle, int newVal);
Introduced in version 9.5.0.96

The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort any DNS operation prior to completion. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire.

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LastErrorHtml
void CkDnsW_getLastErrorHtml(HCkDnsW cHandle, HCkString retval);
const wchar_t *CkDnsW_lastErrorHtml(HCkDnsW cHandle);

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorText
void CkDnsW_getLastErrorText(HCkDnsW cHandle, HCkString retval);
const wchar_t *CkDnsW_lastErrorText(HCkDnsW cHandle);

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorXml
void CkDnsW_getLastErrorXml(HCkDnsW cHandle, HCkString retval);
const wchar_t *CkDnsW_lastErrorXml(HCkDnsW cHandle);

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastMethodSuccess
BOOL CkDnsW_getLastMethodSuccess(HCkDnsW cHandle);
void CkDnsW_putLastMethodSuccess(HCkDnsW cHandle, BOOL newVal);

Indicate whether the last method call succeeded or failed. A value of TRUE indicates success, a value of FALSE indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = TRUE and failure = FALSE.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to TRUE. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

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MaxWaitMs
int CkDnsW_getMaxWaitMs(HCkDnsW cHandle);
void CkDnsW_putMaxWaitMs(HCkDnsW cHandle, int newVal);
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.

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NumNameservers
int CkDnsW_getNumNameservers(HCkDnsW cHandle);
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.

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TlsPref
int CkDnsW_getTlsPref(HCkDnsW cHandle);
void CkDnsW_putTlsPref(HCkDnsW cHandle, int newVal);
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.

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VerboseLogging
BOOL CkDnsW_getVerboseLogging(HCkDnsW cHandle);
void CkDnsW_putVerboseLogging(HCkDnsW cHandle, BOOL newVal);

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.

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Version
void CkDnsW_getVersion(HCkDnsW cHandle, HCkString retval);
const wchar_t *CkDnsW_version(HCkDnsW cHandle);

Version of the component/library, such as "9.5.0.94"

More Information and Examples
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Methods

AddDefaultNameservers
void CkDnsW_AddDefaultNameservers(HCkDnsW cHandle);
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.

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AddNameserver
void CkDnsW_AddNameserver(HCkDnsW cHandle, const wchar_t *ipAddr, BOOL supportsTls);
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.

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GetNameserver
BOOL CkDnsW_GetNameserver(HCkDnsW cHandle, int index, const wchar_t *outStr);
const wchar_t *CkDnsW_getNameserver(HCkDnsW cHandle, int index);
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.

More Information and Examples
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Query
BOOL CkDnsW_Query(HCkDnsW cHandle, const wchar_t *recordType, const wchar_t *domain, HCkJsonObjectW answer);
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.

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QueryAsync (1)
HCkTaskW CkDnsW_QueryAsync(HCkDnsW cHandle, const wchar_t *recordType, const wchar_t *domain, HCkJsonObjectW answer);
Introduced in version 9.5.0.96

Creates an asynchronous task to call the Query method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns NULL on failure

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RemoveAllNameservers
void CkDnsW_RemoveAllNameservers(HCkDnsW cHandle);
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.

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RemoveNameserver
void CkDnsW_RemoveNameserver(HCkDnsW cHandle, const wchar_t *ipAddr);
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.

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