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IPWorks 2022 .NET Edition

Version 22.0 [Build 8171]

MX Component

Properties   Methods   Events   Configuration Settings   Errors  

The MX component enables querying of mail exchange (MX) records from a Domain Name Server (DNS). That is, it will find out the name(s) of the mail server(s) accepting email for a given email address or domain.

Syntax

nsoftware.IPWorks.Mx

Remarks

The component will attempt to automatically determine the name of a DNS server from the system settings or from the value of the DNSServer property.

The component operates in synchronous or asynchronous mode, depending on the value of the Timeout property. Calling the Resolve method makes the component query the DNSServer. The Response event is fired for each server that handles mail for the email address. The component will fill out the MailServer property with the most preferred mail server and the Status property to "Ok" or an error message.

The RequestId property may be used to identify requests and is used in the Response event. The user may set its value before sending out requests, and then match the responses to the request using the RequestId parameter in the Response event.

Property List


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

DNSPortThe port where the DNS server is listening.
DNSServerThis is the address of the DNS server.
IdleThe current status of the component.
LocalHostThe name of the local host or user-assigned IP interface through which connections are initiated or accepted.
MailServerMail server with lowest precedence value (lowest cost to reach).
RequestIdIdentifies each request.
StatusStatus of the request is empty while in progress, 'OK' or error message upon completion.
TimeoutA timeout for the component.

Method List


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

ConfigSets or retrieves a configuration setting.
DoEventsProcesses events from the internal message queue.
InterruptInterrupt the current method.
ResetReset the component.
ResolveResolves an email address.

Event List


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

ErrorInformation about errors during data delivery.
ResponseFired for each MailServer accepting email for the domain.

Configuration Settings


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

CaptureIPPacketInfoUsed to capture the packet information.
DelayHostResolutionWhether the hostname is resolved when RemoteHost is set.
DestinationAddressUsed to get the destination address from the packet information.
DontFragmentUsed to set the Don't Fragment flag of outgoing packets.
LocalHostThe name of the local host through which connections are initiated or accepted.
LocalPortThe port in the local host where the component binds.
MaxPacketSizeThe maximum length of the packets that can be received.
QOSDSCPValueUsed to specify an arbitrary QOS/DSCP setting (optional).
QOSTrafficTypeUsed to specify QOS/DSCP settings (optional).
ShareLocalPortIf set to True, allows more than one instance of the component to be active on the same local port.
UseConnectionDetermines whether to use a connected socket.
UseIPv6Whether or not to use IPv6.
AbsoluteTimeoutDetermines whether timeouts are inactivity timeouts or absolute timeouts.
FirewallDataUsed to send extra data to the firewall.
InBufferSizeThe size in bytes of the incoming queue of the socket.
OutBufferSizeThe size in bytes of the outgoing queue of the socket.
BuildInfoInformation about the product's build.
GUIAvailableTells the component whether or not a message loop is available for processing events.
LicenseInfoInformation about the current license.
UseInternalSecurityAPITells the component whether or not to use the system security libraries or an internal implementation.

DNSPort Property (MX Component)

The port where the DNS server is listening.

Syntax

public int DNSPort { get; set; }
Public Property DNSPort As Integer

Default Value

53

Remarks

This property contains the port where the DNS server is listening. The default value is 53 but you may set this property to any other value for use with experimental servers, etc.

This property is not available at design time.

DNSServer Property (MX Component)

This is the address of the DNS server.

Syntax

public string DNSServer { get; set; }
Public Property DNSServer As String

Default Value

""

Remarks

This property contains the address of the DNS server. The component attempts to find the default DNS server for the machine where it is installed, and provide it in the DNSServer 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 component 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.

This property is not available at design time.

Idle Property (MX Component)

The current status of the component.

Syntax

public bool Idle { get; }
Public ReadOnly Property Idle As Boolean

Default Value

True

Remarks

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

This property is read-only.

LocalHost Property (MX Component)

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

Syntax

public string LocalHost { get; set; }
Public Property LocalHost As String

Default Value

""

Remarks

The LocalHost 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 multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost 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 multi-homed hosts (machines with more than one IP interface).

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

MailServer Property (MX Component)

Mail server with lowest precedence value (lowest cost to reach).

Syntax

public string MailServer { get; }
Public ReadOnly Property MailServer As String

Default Value

""

Remarks

This property contains the mail server with lowest precedence value (lowest cost to reach). After all events are fired this property holds the name of the best mail server for the supplied email address, and the Status property holds the completion status.

This property is read-only.

RequestId Property (MX Component)

Identifies each request.

Syntax

public int RequestId { get; set; }
Public Property RequestId As Integer

Default Value

0

Remarks

This property identifies each request. This may be useful if several email addresses need to be resolved. Each request may be identified by the user before starting a query by calling the Resolve method.

If a custom value is needed for RequestId, the property must be set before resolving an email address. The component increments RequestId automatically after sending each request.

This property is not available at design time.

Status Property (MX Component)

Status of the request is empty while in progress, 'OK' or error message upon completion.

Syntax

public string Status { get; }
Public ReadOnly Property Status As String

Default Value

""

Remarks

This property is reset each time the Resolve method is called. When a response comes from the DNSServer this property is set to "OK" in case of success or to an error message as described in the Response event.

This property is read-only.

Timeout Property (MX Component)

A timeout for the component.

Syntax

public int Timeout { get; set; }
Public Property Timeout As Integer

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 component will wait for the operation to complete before returning control. The component will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of Timeout seconds.

The component will use DoEvents 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 component throws an exception.

Please note that by default, all timeouts are inactivity timeouts, i.e. 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 (MX Component)

Sets or retrieves a configuration setting.

Syntax

public string Config(string configurationString);

Async Version
public async Task<string> Config(string configurationString);
public async Task<string> Config(string configurationString, CancellationToken cancellationToken);
Public Function Config(ByVal ConfigurationString As String) As String

Async Version
Public Function Config(ByVal ConfigurationString As String) As Task(Of String)
Public Function Config(ByVal ConfigurationString As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

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

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, 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.

DoEvents Method (MX Component)

Processes events from the internal message queue.

Syntax

public void DoEvents();
Public Sub DoEvents()

Remarks

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

Interrupt Method (MX Component)

Interrupt the current method.

Syntax

public void Interrupt();

Async Version
public async Task Interrupt();
public async Task Interrupt(CancellationToken cancellationToken);
Public Sub Interrupt()

Async Version
Public Sub Interrupt() As Task
Public Sub Interrupt(cancellationToken As CancellationToken) As Task

Remarks

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

Reset Method (MX Component)

Reset the component.

Syntax

public void Reset();

Async Version
public async Task Reset();
public async Task Reset(CancellationToken cancellationToken);
Public Sub Reset()

Async Version
Public Sub Reset() As Task
Public Sub Reset(cancellationToken As CancellationToken) As Task

Remarks

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

Resolve Method (MX Component)

Resolves an email address.

Syntax

public void Resolve(string emailAddress);

Async Version
public async Task Resolve(string emailAddress);
public async Task Resolve(string emailAddress, CancellationToken cancellationToken);
Public Sub Resolve(ByVal EmailAddress As String)

Async Version
Public Sub Resolve(ByVal EmailAddress As String) As Task
Public Sub Resolve(ByVal EmailAddress As String, cancellationToken As CancellationToken) As Task

Remarks

This method resolves an email address. Calling this method directs the component to query DNSServer at port DNSPort about MX records related to EmailAddress.

The server's response is provided through one or more Response events.

After the query completes, the MailServer property is set to the best mail server and the Status property has the result description of the response.

Valid queries are email addresses like name@company.com or hostnames and domains like domain.com.

Example (Determine Top Priority Mail Server of Email Address)

MXControl.Resolve "email@server.com" While MXControl.MailServer = "" MXControl.DoEvents() End While BestMailServer = MXControl.MailServer

Error Event (MX Component)

Information about errors during data delivery.

Syntax

public event OnErrorHandler OnError;

public delegate void OnErrorHandler(object sender, MxErrorEventArgs e);

public class MxErrorEventArgs : EventArgs {
  public int ErrorCode { get; }

  public string Description { get; }

}
Public Event OnError As OnErrorHandler

Public Delegate Sub OnErrorHandler(sender As Object, e As MxErrorEventArgs)

Public Class MxErrorEventArgs Inherits EventArgs
  Public ReadOnly Property ErrorCode As Integer

  Public ReadOnly Property Description As String

End Class

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component throws an exception.

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

Response Event (MX Component)

Fired for each MailServer accepting email for the domain.

Syntax

public event OnResponseHandler OnResponse;

public delegate void OnResponseHandler(object sender, MxResponseEventArgs e);

public class MxResponseEventArgs : EventArgs {
  public int RequestId { get; }

  public string Domain { get; }

  public string MailServer { get; }

  public int Precedence { get; }

  public int TimeToLive { get; }

  public int StatusCode { get; }

  public string Description { get; }

  public bool Authoritative { get; }

}
Public Event OnResponse As OnResponseHandler

Public Delegate Sub OnResponseHandler(sender As Object, e As MxResponseEventArgs)

Public Class MxResponseEventArgs Inherits EventArgs
  Public ReadOnly Property RequestId As Integer

  Public ReadOnly Property Domain As String

  Public ReadOnly Property MailServer As String

  Public ReadOnly Property Precedence As Integer

  Public ReadOnly Property TimeToLive As Integer

  Public ReadOnly Property StatusCode As Integer

  Public ReadOnly Property Description As String

  Public ReadOnly Property Authoritative As Boolean

End Class

Remarks

A Response event is fired for each mail server handling email for the requested domain. The RequestId parameter identifies the request and equals the value of RequestId property right before the Resolve method is called. MailServer is the name of the server handling email for the requested Domain. A lower Precedence value should be preferred. The TimeToLive parameter gives the validity time in seconds before the DNSServer should be queried again.

Possible values for the StatusCode and Description parameters are:

StatusCodeDescription
0Ok
1Format error
2Server failure
3Name error
4Not implemented
5Refused

After the last Response event is fired, the component sets the MailServer and Status properties to the best MailServer and the error or success code respectively.

Configuration Settings (MX Component)

The component 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 component, access to these internal properties is provided through the Config method.

UDPPort Configuration Settings

CaptureIPPacketInfo:   Used to capture the packet information.

If this is set to true, the component will capture the IP packet information.

The default value for this setting is False.

Note: This setting is only available in Windows.

DelayHostResolution:   Whether the hostname is resolved when RemoteHost is set.

This setting specifies whether a hostname is resolved immediately when RemoteHost is set. If true the component will resolve the hostname and the IP address will be present in the RemoteHost property. If false, the hostname is not resolved until needed by the component when a method to connect or send data is called. If desired, ResolveRemoteHost may called to manually resolve the value in RemoteHost at any time.

The default value is false for the default library and true for the Async library. The default value is false.

DestinationAddress:   Used to get the destination address from the packet information.

If CaptureIPPacketInfo is set to true, then this will be populated with the packet's destination address when a packet is received. This information will be accessible in the DataIn event.

Note: This setting is only available in Windows.

DontFragment:   Used to set the Don't Fragment flag of outgoing packets.

When set to True, packets sent by the component will have the Don't Fragment flag set. The default value is False.

LocalHost:   The name of the local host through which connections are initiated or accepted.

The LocalHost setting 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 multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost setting 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 multi-homed hosts (machines with more than one IP interface).

LocalPort:   The port in the local host where the component binds.

This must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting this to 0 (default) enables the system to choose a port at random. The chosen port will be shown by LocalPort after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set this when a connection is active will generate an error.

This; setting is useful when trying to connect to services that require a trusted port in the client side. An example is the remote shell (rsh) service in UNIX systems.

MaxPacketSize:   The maximum length of the packets that can be received.

This setting specifies the maximum size of the datagrams that the component will accept without truncation.

QOSDSCPValue:   Used to specify an arbitrary QOS/DSCP setting (optional).

UseConnection must be True to use this setting. This option allows you to specify an arbitrary DSCP value between 0 and 63. The default is 0. When set to the default value the component will not set a DSCP value.

Note: This setting uses the qWAVE API is only available on Windows 7, Windows Server 2008 R2, and later.

QOSTrafficType:   Used to specify QOS/DSCP settings (optional).

UseConnection must be True to use this setting. You may specify either the text or integer values: BestEffort (0), Background (1), ExcellentEffort (2), AudioVideo (3), Voice (4), and Control (5).

Note: This setting uses the qWAVE API which is only available on Windows Vista and Windows Server 2008 or above.

Note: QOSTrafficType must be set before setting Active to true.

ShareLocalPort:   If set to True, allows more than one instance of the component to be active on the same local port.

This option must be set before the component is activated through the Active property or it will have no effect.

The default value for this setting is False.

UseConnection:   Determines whether to use a connected socket.

UseConnection specifies whether the component should use a connected socket or not. The connection is defined as an association in between the local address/port and the remote address/port. As such, this is not a connection in the traditional TCP sense. What it means is only that the component will send and receive data only to and from the specified destination.

The default value for this setting is False.

UseIPv6:   Whether or not to use IPv6.

By default, the component expects an IPv4 address for local and remote host properties, and will create an IPv4 socket. To use IPv6 instead, set this to True.

Socket Configuration Settings

AbsoluteTimeout:   Determines whether timeouts are inactivity timeouts or absolute timeouts.

If AbsoluteTimeout is set to True, any method which does not complete within Timeout seconds will be aborted. By default, AbsoluteTimeout is False, and the timeout is an inactivity timeout.

Note: This option is not valid for UDP ports.

FirewallData:   Used to send extra data to the firewall.

When the firewall is a tunneling proxy, use this property to send custom (additional) headers to the firewall (e.g. headers for custom authentication schemes).

InBufferSize:   The size in bytes of the incoming queue of the socket.

This is the size of an internal queue in the TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be receiving. Increasing the value of the InBufferSize setting can provide significant improvements in performance in some cases.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the InBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.

OutBufferSize:   The size in bytes of the outgoing queue of the socket.

This is the size of an internal queue in the TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be sending. Increasing the value of the OutBufferSize setting can provide significant improvements in performance in some cases.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the OutBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.

Base Configuration Settings

BuildInfo:   Information about the product's build.

When queried, this setting will return a string containing information about the product's build.

GUIAvailable:   Tells the component whether or not a message loop is available for processing events.

In a GUI-based application, long-running blocking operations may cause the application to stop responding to input until the operation returns. The component will attempt to discover whether or not the application has a message loop and, if one is discovered, it will process events in that message loop during any such blocking operation.

In some non-GUI applications, an invalid message loop may be discovered that will result in errant behavior. In these cases, setting GUIAvailable to false will ensure that the component does not attempt to process external events.

LicenseInfo:   Information about the current license.

When queried, this setting will return a string containing information about the license this instance of a component is using. It will return the following information:

  • Product: The product the license is for.
  • Product Key: The key the license was generated from.
  • License Source: Where the license was found (e.g., RuntimeLicense, License File).
  • License Type: The type of license installed (e.g., Royalty Free, Single Server).
UseInternalSecurityAPI:   Tells the component whether or not to use the system security libraries or an internal implementation.

By default the component will use the system security libraries to perform cryptographic functions. When set to False calls to unmanaged code will be made. In certain environments this is not desirable. To use a completely managed security implementation set this setting to True. Setting this to True tells the component to use the internal implementation instead of using the system's security API.

Note: This setting is static. The value set is applicable to all components used in the application.

When this value is set the product's system DLL is no longer required as a reference, as all unmanaged code is stored in that file.

Trappable Errors (MX Component)

MX Errors

290   No DNS server specified.
530   Busy performing current action.

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

UDPPort Errors

104   UDPPort is already Active.
106   You cannot change the LocalPort while the component is Active.
107   You cannot change the LocalHost at this time. A connection is in progress.
109   The component must be Active for this operation.
112   Cannot change MaxPacketSize while the component is Active.
113   Cannot change ShareLocalPort option while the component is Active.
114   Cannot change RemoteHost when UseConnection is set and the component Active.
115   Cannot change RemotePort when UseConnection is set and the component is Active.
116   RemotePort can't be zero when UseConnection is set. Please specify a valid service port number.
117   Cannot change UseConnection while the component is Active.
118   Message can't be longer than MaxPacketSize.
119   Message too short.
434   Unable to convert string to selected CodePage

SSL Errors

270   Cannot load specified security library.
271   Cannot open certificate store.
272   Cannot find specified certificate.
273   Cannot acquire security credentials.
274   Cannot find certificate chain.
275   Cannot verify certificate chain.
276   Error during handshake.
280   Error verifying certificate.
281   Could not find client certificate.
282   Could not find server certificate.
283   Error encrypting data.
284   Error decrypting data.

TCP/IP Errors

10004   [10004] Interrupted system call.
10009   [10009] Bad file number.
10013   [10013] Access denied.
10014   [10014] Bad address.
10022   [10022] Invalid argument.
10024   [10024] Too many open files.
10035   [10035] Operation would block.
10036   [10036] Operation now in progress.
10037   [10037] Operation already in progress.
10038   [10038] Socket operation on non-socket.
10039   [10039] Destination address required.
10040   [10040] Message too long.
10041   [10041] Protocol wrong type for socket.
10042   [10042] Bad protocol option.
10043   [10043] Protocol not supported.
10044   [10044] Socket type not supported.
10045   [10045] Operation not supported on socket.
10046   [10046] Protocol family not supported.
10047   [10047] Address family not supported by protocol family.
10048   [10048] Address already in use.
10049   [10049] Can't assign requested address.
10050   [10050] Network is down.
10051   [10051] Network is unreachable.
10052   [10052] Net dropped connection or reset.
10053   [10053] Software caused connection abort.
10054   [10054] Connection reset by peer.
10055   [10055] No buffer space available.
10056   [10056] Socket is already connected.
10057   [10057] Socket is not connected.
10058   [10058] Can't send after socket shutdown.
10059   [10059] Too many references, can't splice.
10060   [10060] Connection timed out.
10061   [10061] Connection refused.
10062   [10062] Too many levels of symbolic links.
10063   [10063] File name too long.
10064   [10064] Host is down.
10065   [10065] No route to host.
10066   [10066] Directory not empty
10067   [10067] Too many processes.
10068   [10068] Too many users.
10069   [10069] Disc Quota Exceeded.
10070   [10070] Stale NFS file handle.
10071   [10071] Too many levels of remote in path.
10091   [10091] Network subsystem is unavailable.
10092   [10092] WINSOCK DLL Version out of range.
10093   [10093] Winsock not loaded yet.
11001   [11001] Host not found.
11002   [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
11003   [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
11004   [11004] Valid name, no data record (check DNS setup).

Copyright (c) 2022 /n software inc. - All rights reserved.
IPWorks 2022 .NET Edition - Version 22.0 [Build 8171]