DNS Class

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The DNS class is used to query DNS for record information.

Syntax

class ipworks.DNS

Remarks

The DNS class queries a DNS server for records as specified in RFC 1035 and other relevant RFCs. The class property query_type indicates the record to be queried. Calling query will initiate the query.

Once the query is complete, a single on_response event will fire and the record properties will be filled. status_code is the server's success or fail code, and status is a standard string interpretation of the code.

The records are contained in the records properties. The programming interface is designed to allow a full walk of the records in the DNS response, including provisions for handling new record types.

The class operates synchronously by default (i.e., it waits for a response before returning control to the caller); however, the class also may operate asynchronously (i.e., return control immediately), by setting timeout to 0. Please see the timeout property for more information.

Property List

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The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the class with short descriptions. Click on the links for further details.

dns_port Property

This is the port to connect to on the DNS server.

Syntax

def get_dns_port() -> int: ...
def set_dns_port(value: int) -> None: ...

dns_port = property(get_dns_port, set_dns_port)

Default Value

53

Remarks

This property contains the port to connect to on the DNS server. A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

dns_server Property

This is the address of the DNS server.

Syntax

def get_dns_server() -> str: ...
def set_dns_server(value: str) -> None: ...

dns_server = property(get_dns_server, set_dns_server)

Default Value

""

Remarks

This property contains the address of the DNS server. The class attempts to find the default DNS server for the machine where it is installed, and provide it in the dns_server property. You may change it to any particular DNS server you want to query. While any internet host running a DNS service will suffice, it is preferable to use either the DNS server for your network or the DNS server for the domain that you are querying.

If the class cannot determine the default DNS server address, the property value will be an empty string.

Note: Automatic discovery of the default DNS server is not supported in the Java edition.

idle Property

The current status of the class.

Syntax

def get_idle() -> bool: ...

idle = property(get_idle, None)

Default Value

TRUE

Remarks

This property will be False if the component is currently busy (communicating or waiting for an answer), and True at all other times.

This property is read-only.

local_host Property

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

def get_local_host() -> str: ...
def set_local_host(value: str) -> None: ...

local_host = property(get_local_host, set_local_host)

Default Value

""

Remarks

This property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the class initiate connections (or accept in the case of server classs) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the class is connected, the local_host property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

Note: local_host is not persistent. You must always set it in code, and never in the property window.

protocol Property

This protocol is used for the DNS request.

Syntax

def get_protocol() -> int: ...
def set_protocol(value: int) -> None: ...

protocol = property(get_protocol, set_protocol)

Default Value

0

Remarks

This property specifies the protocol used for the DNS request when query is called. Possible values include the following:

query_type Property

This is the type of record to query.

Syntax

def get_query_type() -> int: ...
def set_query_type(value: int) -> None: ...

query_type = property(get_query_type, set_query_type)

Default Value

1

Remarks

Before a query is attempted, this property must be set to the desired record type. The records are defined as follows:

record_count Property

The number of records in the Record arrays.

Syntax

def get_record_count() -> int: ...

record_count = property(get_record_count, None)

Default Value

0

Remarks

This property controls the size of the following arrays:

• record_data
• record_domain
• record_field_count
• record_field_index
• record_field_name
• record_field_value
• record_ttl
• record_type
• record_type_name

The array indices start at 0 and end at record_count - 1.

This property is read-only.

record_domain Property

This property contains the domain name associated with the selected response record, at RecordIndex .

Syntax

def get_record_domain(record_index: int) -> str: ...

Default Value

""

Remarks

This property contains the domain name associated with the selected response record, at RecordIndex.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_field_count Property

This property contains the number of properties in the current record.

Syntax

def get_record_field_count(record_index: int) -> int: ...

Default Value

0

Remarks

This property contains the number of properties in the current record.

After a successful query, the field values for each record will be provided in the records properties.

To retrieve a particular field value for a record, first set record_field_index to a valid response field index and then query records collection for the value of that field.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_field_index Property

This property contains the index of the selected property of the current record.

Syntax

def get_record_field_index(record_index: int) -> int: ...
def set_record_field_index(record_index: int, value: int) -> None: ...

Default Value

1

Remarks

This property contains the index of the selected property of the current record. record_field_index valid values are from 0 to (record_field_count -1).

After a successful query, the field values for each record will be provided in the records properties.

To retrieve a particular field value for a record, first set record_field_index to a valid response field index and then query records collection for the value of that field.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

record_field_name Property

This property contains the name of the property selected by FieldIndex .

Syntax

def get_record_field_name(record_index: int) -> str: ...

Default Value

"0"

Remarks

This property contains the name of the field selected by record_field_index. Field names are different depending on the record type. For example, an MX record type will contain two properties: PREFERENCE and EXCHANGE, but an SOA record type contains seven properties.

Field names:

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_field_value Property

This property contains the value of the property selected by FieldIndex .

Syntax

def get_record_field_value(record_index: int) -> bytes: ...

Default Value

""

Remarks

This property contains the value of the field selected by record_field_index.

After a successful query, the field values for each record will be provided in the records properties.

To retrieve a particular field value for a record, first set record_field_index to a valid response field index and then query records collection for the value of that field.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_data Property

This property contains the full record data as received from the DNS server.

Syntax

def get_record_data(record_index: int) -> bytes: ...

Default Value

""

Remarks

This property contains the full record data as received from the DNS server.

After a successful query, the field values for each record will be provided in the records properties.

To retrieve a particular field value for a record, first set record_field_index to a valid response field index and then query records collection for the value of that field.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_type Property

This property contains the record type.

Syntax

def get_record_type(record_index: int) -> int: ...

Default Value

1

Remarks

This property contains the record type.

Record types correspond to query_type and are defined as follows:

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_type_name Property

This property contains the string representation of the current record type defined by RecordType .

Syntax

def get_record_type_name(record_index: int) -> str: ...

Default Value

""

Remarks

This property contains the string representation of the current record type defined by record_type.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_ttl Property

This property contains the record Time to Live (TTL) value.

Syntax

def get_record_ttl(record_index: int) -> int: ...

Default Value

0

Remarks

This property contains the record Time to Live (TTL) value. The TTL specifies the time interval in seconds that the record is valid, or the time interval that the record can be cached before the DNS server should be queried again.

The record_index parameter specifies the index of the item in the array. The size of the array is controlled by the record_count property.

This property is read-only.

record_source Property

The source of records provided in the Records properties.

Syntax

def get_record_source() -> int: ...
def set_record_source(value: int) -> None: ...

record_source = property(get_record_source, set_record_source)

Default Value

0

Remarks

This property contains the source of records provided in the records properties and can have one of the following values:

recursive Property

This determines whether to ask the DNSServer to recursively query other servers.

Syntax

def get_recursive() -> bool: ...
def set_recursive(value: bool) -> None: ...

recursive = property(get_recursive, set_recursive)

Default Value

TRUE

Remarks

If this property is True, the component will tell the DNS server to perform the query recursively. This means that if the DNS server does not have information about the domain being queried, it will send the request to another DNS server.

request_id Property

This is the Id of the current DNS request.

Syntax

def get_request_id() -> int: ...
def set_request_id(value: int) -> None: ...

request_id = property(get_request_id, set_request_id)

Default Value

1

Remarks

This property is the identifier of the request that generated the current response values. Each time the class makes a DNS query, it generates a unique request identifier to track the response.

If a custom value is needed for request_id, the property must be set before sending a request. The class increments request_id automatically after sending each request.

Note: The class fails with an error when a value that is not between 1 and 32,767 is specified.

status Property

This is a standard string interpretation of StatusCode .

Syntax

def get_status() -> str: ...

status = property(get_status, None)

Default Value

""

Remarks

This property contains a standard string interpretation of status_code. For a list of valid error codes and their descriptions, please see the Error Codes section.

This property is read-only.

status_code Property

This contains the success or error code for the DNS query.

Syntax

def get_status_code() -> int: ...

status_code = property(get_status_code, None)

Default Value

0

Remarks

This property contains the success or error code for the DNS query. For a list of valid error codes and their descriptions, please see the Error Codes section.

This property is read-only.

timeout Property

This property includes the timeout for the class.

Syntax

def get_timeout() -> int: ...
def set_timeout(value: int) -> None: ...

timeout = property(get_timeout, set_timeout)

Default Value

60

Remarks

If the timeout property is set to 0, all operations return immediately, potentially failing with a WOULDBLOCK error if data cannot be sent immediately.

If timeout is set to a positive value, data is sent in a blocking manner and the class will wait for the operation to complete before returning control. The class will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of timeout seconds.

The class will use do_events to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not freeze and remains responsive.

If timeout expires, and the operation is not yet complete, the class fails with an error.

Note: By default, all timeouts are inactivity timeouts, that is, the timeout period is extended by timeout seconds when any amount of data is successfully sent or received.

The default value for the timeout property is 60 seconds.

config Method

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

Remarks

config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

do_events Method

This method processes events from the internal message queue.

Syntax

def do_events() -> None: ...

Remarks

When do_events is called, the class processes any available events. If no events are available, it waits for a preset period of time, and then returns.

get_field_value Method

This gets the value of the field indicated from a record.

Syntax

def get_field_value(record_index: int, field_name: str) -> str: ...

Remarks

This method will get the value of the DNS record field specified by FieldName from the DNS record at RecordIndex. If no such field exists for that record type, the component fails with an error.

interrupt Method

This method interrupts the current method.

Syntax

def interrupt() -> None: ...

Remarks

If there is no method in progress, interrupt simply returns, doing nothing.

query Method

This method queries a domain.

Syntax

def query(domain: str) -> None: ...

Remarks

This method will query the host Domain for any records of the type in query_type. After the query, request_id is the identifier corresponding to the request. Once the query is complete, a single on_response event will fire. The following properties will contain the results:

reset Method

This method will reset the class.

Syntax

def reset() -> None: ...

Remarks

This method will reset the class's properties to their default values.

on_error Event

Fired when information is available about errors during data delivery.

Syntax

class DNSErrorEventParams(object):
  @property
  def error_code() -> int: ...

  @property
  def description() -> str: ...

# In class DNS:
@property
def on_error() -> Callable[[DNSErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[DNSErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

on_log Event

This event fires once for each log message.

Syntax

class DNSLogEventParams(object):
  @property
  def log_level() -> int: ...

  @property
  def message() -> str: ...

  @property
  def log_type() -> str: ...

# In class DNS:
@property
def on_log() -> Callable[[DNSLogEventParams], None]: ...
@on_log.setter
def on_log(event_hook: Callable[[DNSLogEventParams], None]) -> None: ...

Remarks

This event fires once for each log message generated by the class. The verbosity is controlled by the LogLevel setting.

LogLevel indicates the level of message. Possible values are as follows:

The value 1 (Info) logs basic information, including the URL, HTTP version, and status details.

The value 2 (Verbose) logs additional information about the request and response.

The value 3 (Debug) logs the headers and body for both the request and response, as well as additional debug information (if any).

Message is the log entry.

LogType identifies the type of log entry. Possible values are as follows:

• "Info"
• "RequestHeaders"
• "ResponseHeaders"
• "RequestBody"
• "ResponseBody"
• "ProxyRequest"
• "ProxyResponse"
• "FirewallRequest"
• "FirewallResponse"

on_response Event

This event fires after a DNS query.

Syntax

class DNSResponseEventParams(object):
  @property
  def request_id() -> int: ...

  @property
  def domain() -> str: ...

  @property
  def status_code() -> int: ...

  @property
  def description() -> str: ...

  @property
  def authoritative() -> bool: ...

# In class DNS:
@property
def on_response() -> Callable[[DNSResponseEventParams], None]: ...
@on_response.setter
def on_response(event_hook: Callable[[DNSResponseEventParams], None]) -> None: ...

Remarks

The on_response event will fire after a call to query. The RequestId parameter contains the request Id associated with the original query. Domain is the domain of the query. The Authoritative parameter is true if the response is from an authoritative name server. If there is an error returned by the server, StatusCode and Description provide them.

Once the query is complete, a single on_response event will fire. The following properties will contain the results:

on_ssl_server_authentication Event

This event fires when connecting to the server.

Syntax

class DNSSSLServerAuthenticationEventParams(object):
  @property
  def remote_address() -> str: ...

  @property
  def remote_port() -> int: ...

  @property
  def cert_encoded() -> bytes: ...

  @property
  def cert_subject() -> str: ...

  @property
  def cert_issuer() -> str: ...

  @property
  def status() -> str: ...

  @property
  def accept() -> bool: ...
  @accept.setter
  def accept(value) -> None: ...

# In class DNS:
@property
def on_ssl_server_authentication() -> Callable[[DNSSSLServerAuthenticationEventParams], None]: ...
@on_ssl_server_authentication.setter
def on_ssl_server_authentication(event_hook: Callable[[DNSSSLServerAuthenticationEventParams], None]) -> None: ...

Remarks

This event allows the client to decide whether or not to continue with the connection process. The Accept parameter recommends whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

When Accept is False, Status shows why the verification failed (otherwise, Status contains the string "OK"). If the client decides to continue, you can override and accept the certificate by setting the Accept parameter to True.

RemoteAddress is the IP address of the server.

RemotePort is the source port of the server.

CertEncoded is the Base64-encoded certificate presented by the server.

CertSubject is the subject of the certificate presented by the server.

CertIssuer is the subject of the issuer of the certificate presented by the server.

Status is the status of the certificate.

Accept defines whether the certificate is accepted.

on_ssl_status Event

This shows the progress of the secure connection.

Syntax

class DNSSSLStatusEventParams(object):
  @property
  def remote_address() -> str: ...

  @property
  def remote_port() -> int: ...

  @property
  def message() -> str: ...

# In class DNS:
@property
def on_ssl_status() -> Callable[[DNSSSLStatusEventParams], None]: ...
@on_ssl_status.setter
def on_ssl_status(event_hook: Callable[[DNSSSLStatusEventParams], None]) -> None: ...

Remarks

The event is fired for informational and logging purposes only. It is used to track the progress of the connection.

RemoteAddress is the IP address of the remote machine.

RemotePort is the port of the remote machine.

Message is the log message.

DNS Config Settings

The class accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

DNS Config Settings

UDP Config Settings

Socket Config Settings

Base Config Settings

DNS Errors

DNS Errors

The class may also return one of the following error codes, which are inherited from other classes.

UDP Errors

SSL Errors

TCP/IP Errors