MX Control
Properties Methods Events Config Settings Errors
The MX control enables querying of mail exchange (MX) records from a Domain Name Server (DNS). Thus, it will find out the names of the mail servers accepting email for a given email address or domain.
Syntax
MX
Remarks
The control will attempt to automatically determine the name of a DNS server from the system settings or from the value of the DNSServer property.
The control operates in synchronous or asynchronous mode, depending on the value of the Timeout property. Calling the Resolve method makes the control query the DNSServer. The Response event is fired for each server that handles mail for the email address. The control will fill out the MailServer property with the most preferred mail server and will set the Status property to "OK" or to an error message upon completion.
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 control with short descriptions. Click on the links for further details.
DNSPort | This property includes the port where the DNS server is listening. |
DNSServer | This is the address of the DNS server. |
Idle | The current status of the control. |
LocalHost | The name of the local host or user-assigned IP interface through which connections are initiated or accepted. |
MailServer | This property includes the mail server with the lowest precedence value (lowest cost to reach). |
RequestId | This property identifies each request. |
Status | The status of the request is empty while in progress. This property is set to OK or to an error message upon completion. |
Timeout | A timeout for the control. |
Method List
The following is the full list of the methods of the control with short descriptions. Click on the links for further details.
Config | Sets or retrieves a configuration setting. |
DoEvents | Processes events from the internal message queue. |
Interrupt | Interrupt the current method. |
Reset | Reset the control. |
Resolve | This method resolves an email address. |
Event List
The following is the full list of the events fired by the control with short descriptions. Click on the links for further details.
Error | Fired when information is available about errors during data delivery. |
Response | This event is fired for each MailServer accepting email for the domain. |
Config Settings
The following is a list of config settings for the control with short descriptions. Click on the links for further details.
CaptureIPPacketInfo | Used to capture the packet information. |
DelayHostResolution | Whether the hostname is resolved when RemoteHost is set. |
DestinationAddress | Used to get the destination address from the packet information. |
DontFragment | Used to set the Don't Fragment flag of outgoing packets. |
LocalHost | The name of the local host through which connections are initiated or accepted. |
LocalPort | The port in the local host where the control binds. |
MaxPacketSize | The maximum length of the packets that can be received. |
QOSDSCPValue | Used to specify an arbitrary QOS/DSCP setting (optional). |
QOSTrafficType | Used to specify QOS/DSCP settings (optional). |
ShareLocalPort | If set to True, allows more than one instance of the control to be active on the same local port. |
UseConnection | Determines whether to use a connected socket. |
UseIPv6 | Whether or not to use IPv6. |
AbsoluteTimeout | Determines whether timeouts are inactivity timeouts or absolute timeouts. |
FirewallData | Used to send extra data to the firewall. |
InBufferSize | The size in bytes of the incoming queue of the socket. |
OutBufferSize | The size in bytes of the outgoing queue of the socket. |
CodePage | The system code page used for Unicode to Multibyte translations. |
MaskSensitive | Whether sensitive data is masked in log messages. |
UseInternalSecurityAPI | Whether or not to use the system security libraries or an internal implementation. |
DNSPort Property (MX Control)
This property includes the port where the DNS server is listening.
Syntax
mxcontrol.DNSPort[=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 and such.
This property is not available at design time.
Data Type
Integer
DNSServer Property (MX Control)
This is the address of the DNS server.
Syntax
mxcontrol.DNSServer[=string]
Default Value
""
Remarks
This property contains the address of the DNS server. The control 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 control 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.
Data Type
String
Idle Property (MX Control)
The current status of the control.
Syntax
mxcontrol.Idle
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.
Data Type
Boolean
LocalHost Property (MX Control)
The name of the local host or user-assigned IP interface through which connections are initiated or accepted.
Syntax
mxcontrol.LocalHost[=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 control initiate connections (or accept in the case of server controls) only through that interface.
If the control 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.
Data Type
String
MailServer Property (MX Control)
This property includes the mail server with the lowest precedence value (lowest cost to reach).
Syntax
mxcontrol.MailServer
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.
Data Type
String
RequestId Property (MX Control)
This property identifies each request.
Syntax
mxcontrol.RequestId[=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 control increments RequestId automatically after sending each request.
This property is not available at design time.
Data Type
Integer
Status Property (MX Control)
The status of the request is empty while in progress. This property is set to OK or to an error message upon completion.
Syntax
mxcontrol.Status
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.
Data Type
String
Timeout Property (MX Control)
A timeout for the control.
Syntax
mxcontrol.Timeout[=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 control will wait for the operation to complete before returning control. The control will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of Timeout seconds.
The control 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 control fails with an error.
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.
Data Type
Integer
Config Method (MX Control)
Sets or retrieves a configuration setting.
Syntax
mxcontrol.Config ConfigurationString
Remarks
Config is a generic method available in every control. It is used to set and retrieve configuration settings for the control.
These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, 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 Control)
Processes events from the internal message queue.
Syntax
mxcontrol.DoEvents
Remarks
When DoEvents is called, the control processes any available events. If no events are available, it waits for a preset period of time, and then returns.
Interrupt Method (MX Control)
Interrupt the current method.
Syntax
mxcontrol.Interrupt
Remarks
If there is no method in progress, Interrupt simply returns, doing nothing.
Reset Method (MX Control)
Reset the control.
Syntax
mxcontrol.Reset
Remarks
This method will reset the control's properties to their default values.
Resolve Method (MX Control)
This method resolves an email address.
Syntax
mxcontrol.Resolve EmailAddress
Remarks
This method resolves an email address. Calling this method directs the control 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 includes 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 Control)
Fired when information is available about errors during data delivery.
Syntax
Sub mxcontrol_Error(ErrorCode As Integer, Description As String)
Remarks
The Error event is fired in case of exceptional conditions during message processing. Normally the control 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.
Response Event (MX Control)
This event is fired for each MailServer accepting email for the domain.
Syntax
Sub mxcontrol_Response(RequestId As Integer, Domain As String, MailServer As String, Precedence As Integer, TimeToLive As Integer, StatusCode As Integer, Description As String, Authoritative As Boolean)
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 the 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 as follows:
StatusCode | Description |
0 | Ok |
1 | Format error |
2 | Server failure |
3 | Name error |
4 | Not implemented |
5 | Refused |
After the last Response event is fired, the control sets the MailServer and Status properties to the best MailServer and the error or success code, respectively.
Config Settings (MX Control)
The control 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 control, access to these internal properties is provided through the Config method.UDP Config Settings
The default value for this setting is False.
Note: This setting is only available in Windows.
The default value is .
Note: This setting is only available in Windows.
In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the control initiate connections (or accept in the case of server controls) only through that interface.
If the control 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).
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.
Note: This setting uses the qWAVE API is only available on Windows 7, Windows Server 2008 R2, and later.
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.
The default value for this setting is False.
The default value for this setting is False.
Socket Config Settings
Note: This option is not valid for UDP ports.
Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the control is activated the InBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.
Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the control is activated the OutBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.
Base Config Settings
The following is a list of valid code page identifiers:
Identifier | Name |
037 | IBM EBCDIC - U.S./Canada |
437 | OEM - United States |
500 | IBM EBCDIC - International |
708 | Arabic - ASMO 708 |
709 | Arabic - ASMO 449+, BCON V4 |
710 | Arabic - Transparent Arabic |
720 | Arabic - Transparent ASMO |
737 | OEM - Greek (formerly 437G) |
775 | OEM - Baltic |
850 | OEM - Multilingual Latin I |
852 | OEM - Latin II |
855 | OEM - Cyrillic (primarily Russian) |
857 | OEM - Turkish |
858 | OEM - Multilingual Latin I + Euro symbol |
860 | OEM - Portuguese |
861 | OEM - Icelandic |
862 | OEM - Hebrew |
863 | OEM - Canadian-French |
864 | OEM - Arabic |
865 | OEM - Nordic |
866 | OEM - Russian |
869 | OEM - Modern Greek |
870 | IBM EBCDIC - Multilingual/ROECE (Latin-2) |
874 | ANSI/OEM - Thai (same as 28605, ISO 8859-15) |
875 | IBM EBCDIC - Modern Greek |
932 | ANSI/OEM - Japanese, Shift-JIS |
936 | ANSI/OEM - Simplified Chinese (PRC, Singapore) |
949 | ANSI/OEM - Korean (Unified Hangul Code) |
950 | ANSI/OEM - Traditional Chinese (Taiwan; Hong Kong SAR, PRC) |
1026 | IBM EBCDIC - Turkish (Latin-5) |
1047 | IBM EBCDIC - Latin 1/Open System |
1140 | IBM EBCDIC - U.S./Canada (037 + Euro symbol) |
1141 | IBM EBCDIC - Germany (20273 + Euro symbol) |
1142 | IBM EBCDIC - Denmark/Norway (20277 + Euro symbol) |
1143 | IBM EBCDIC - Finland/Sweden (20278 + Euro symbol) |
1144 | IBM EBCDIC - Italy (20280 + Euro symbol) |
1145 | IBM EBCDIC - Latin America/Spain (20284 + Euro symbol) |
1146 | IBM EBCDIC - United Kingdom (20285 + Euro symbol) |
1147 | IBM EBCDIC - France (20297 + Euro symbol) |
1148 | IBM EBCDIC - International (500 + Euro symbol) |
1149 | IBM EBCDIC - Icelandic (20871 + Euro symbol) |
1200 | Unicode UCS-2 Little-Endian (BMP of ISO 10646) |
1201 | Unicode UCS-2 Big-Endian |
1250 | ANSI - Central European |
1251 | ANSI - Cyrillic |
1252 | ANSI - Latin I |
1253 | ANSI - Greek |
1254 | ANSI - Turkish |
1255 | ANSI - Hebrew |
1256 | ANSI - Arabic |
1257 | ANSI - Baltic |
1258 | ANSI/OEM - Vietnamese |
1361 | Korean (Johab) |
10000 | MAC - Roman |
10001 | MAC - Japanese |
10002 | MAC - Traditional Chinese (Big5) |
10003 | MAC - Korean |
10004 | MAC - Arabic |
10005 | MAC - Hebrew |
10006 | MAC - Greek I |
10007 | MAC - Cyrillic |
10008 | MAC - Simplified Chinese (GB 2312) |
10010 | MAC - Romania |
10017 | MAC - Ukraine |
10021 | MAC - Thai |
10029 | MAC - Latin II |
10079 | MAC - Icelandic |
10081 | MAC - Turkish |
10082 | MAC - Croatia |
12000 | Unicode UCS-4 Little-Endian |
12001 | Unicode UCS-4 Big-Endian |
20000 | CNS - Taiwan |
20001 | TCA - Taiwan |
20002 | Eten - Taiwan |
20003 | IBM5550 - Taiwan |
20004 | TeleText - Taiwan |
20005 | Wang - Taiwan |
20105 | IA5 IRV International Alphabet No. 5 (7-bit) |
20106 | IA5 German (7-bit) |
20107 | IA5 Swedish (7-bit) |
20108 | IA5 Norwegian (7-bit) |
20127 | US-ASCII (7-bit) |
20261 | T.61 |
20269 | ISO 6937 Non-Spacing Accent |
20273 | IBM EBCDIC - Germany |
20277 | IBM EBCDIC - Denmark/Norway |
20278 | IBM EBCDIC - Finland/Sweden |
20280 | IBM EBCDIC - Italy |
20284 | IBM EBCDIC - Latin America/Spain |
20285 | IBM EBCDIC - United Kingdom |
20290 | IBM EBCDIC - Japanese Katakana Extended |
20297 | IBM EBCDIC - France |
20420 | IBM EBCDIC - Arabic |
20423 | IBM EBCDIC - Greek |
20424 | IBM EBCDIC - Hebrew |
20833 | IBM EBCDIC - Korean Extended |
20838 | IBM EBCDIC - Thai |
20866 | Russian - KOI8-R |
20871 | IBM EBCDIC - Icelandic |
20880 | IBM EBCDIC - Cyrillic (Russian) |
20905 | IBM EBCDIC - Turkish |
20924 | IBM EBCDIC - Latin-1/Open System (1047 + Euro symbol) |
20932 | JIS X 0208-1990 & 0121-1990 |
20936 | Simplified Chinese (GB2312) |
21025 | IBM EBCDIC - Cyrillic (Serbian, Bulgarian) |
21027 | Extended Alpha Lowercase |
21866 | Ukrainian (KOI8-U) |
28591 | ISO 8859-1 Latin I |
28592 | ISO 8859-2 Central Europe |
28593 | ISO 8859-3 Latin 3 |
28594 | ISO 8859-4 Baltic |
28595 | ISO 8859-5 Cyrillic |
28596 | ISO 8859-6 Arabic |
28597 | ISO 8859-7 Greek |
28598 | ISO 8859-8 Hebrew |
28599 | ISO 8859-9 Latin 5 |
28605 | ISO 8859-15 Latin 9 |
29001 | Europa 3 |
38598 | ISO 8859-8 Hebrew |
50220 | ISO 2022 Japanese with no halfwidth Katakana |
50221 | ISO 2022 Japanese with halfwidth Katakana |
50222 | ISO 2022 Japanese JIS X 0201-1989 |
50225 | ISO 2022 Korean |
50227 | ISO 2022 Simplified Chinese |
50229 | ISO 2022 Traditional Chinese |
50930 | Japanese (Katakana) Extended |
50931 | US/Canada and Japanese |
50933 | Korean Extended and Korean |
50935 | Simplified Chinese Extended and Simplified Chinese |
50936 | Simplified Chinese |
50937 | US/Canada and Traditional Chinese |
50939 | Japanese (Latin) Extended and Japanese |
51932 | EUC - Japanese |
51936 | EUC - Simplified Chinese |
51949 | EUC - Korean |
51950 | EUC - Traditional Chinese |
52936 | HZ-GB2312 Simplified Chinese |
54936 | Windows XP: GB18030 Simplified Chinese (4 Byte) |
57002 | ISCII Devanagari |
57003 | ISCII Bengali |
57004 | ISCII Tamil |
57005 | ISCII Telugu |
57006 | ISCII Assamese |
57007 | ISCII Oriya |
57008 | ISCII Kannada |
57009 | ISCII Malayalam |
57010 | ISCII Gujarati |
57011 | ISCII Punjabi |
65000 | Unicode UTF-7 |
65001 | Unicode UTF-8 |
Identifier | Name |
1 | ASCII |
2 | NEXTSTEP |
3 | JapaneseEUC |
4 | UTF8 |
5 | ISOLatin1 |
6 | Symbol |
7 | NonLossyASCII |
8 | ShiftJIS |
9 | ISOLatin2 |
10 | Unicode |
11 | WindowsCP1251 |
12 | WindowsCP1252 |
13 | WindowsCP1253 |
14 | WindowsCP1254 |
15 | WindowsCP1250 |
21 | ISO2022JP |
30 | MacOSRoman |
10 | UTF16String |
0x90000100 | UTF16BigEndian |
0x94000100 | UTF16LittleEndian |
0x8c000100 | UTF32String |
0x98000100 | UTF32BigEndian |
0x9c000100 | UTF32LittleEndian |
65536 | Proprietary |
This setting only works on these controls: AS3Receiver, AS3Sender, Atom, Client(3DS), FTP, FTPServer, IMAP, OFTPClient, SSHClient, SCP, Server(3DS), Sexec, SFTP, SFTPServer, SSHServer, TCPClient, TCPServer.
Setting this configuration setting to tells the control to use the internal implementation instead of using the system security libraries.
This setting is set to by default on all platforms.
Trappable Errors (MX Control)
MX Errors
20291 No DNS server specified. | |
20531 Busy performing current action. |
The control may also return one of the following error codes, which are inherited from other controls.
UDP Errors
20105 UDP is already Active. | |
20107 You cannot change the LocalPort while the control is Active. | |
20108 You cannot change the LocalHost at this time. A connection is in progress. | |
20110 The control must be Active for this operation. | |
20113 Cannot change MaxPacketSize while the control is Active. | |
20114 Cannot change ShareLocalPort option while the control is Active. | |
20115 Cannot change RemoteHost when UseConnection is set and the control Active. | |
20116 Cannot change RemotePort when UseConnection is set and the control is Active. | |
20117 RemotePort can't be zero when UseConnection is set. Please specify a valid service port number. | |
20118 Cannot change UseConnection while the control is Active. | |
20119 Message can't be longer than MaxPacketSize. | |
20120 Message too short. | |
20435 Unable to convert string to selected CodePage |
SSL Errors
20271 Cannot load specified security library. | |
20272 Cannot open certificate store. | |
20273 Cannot find specified certificate. | |
20274 Cannot acquire security credentials. | |
20275 Cannot find certificate chain. | |
20276 Cannot verify certificate chain. | |
20277 Error during handshake. | |
20281 Error verifying certificate. | |
20282 Could not find client certificate. | |
20283 Could not find server certificate. | |
20284 Error encrypting data. | |
20285 Error decrypting data. |
TCP/IP Errors
25005 [10004] Interrupted system call. | |
25010 [10009] Bad file number. | |
25014 [10013] Access denied. | |
25015 [10014] Bad address. | |
25023 [10022] Invalid argument. | |
25025 [10024] Too many open files. | |
25036 [10035] Operation would block. | |
25037 [10036] Operation now in progress. | |
25038 [10037] Operation already in progress. | |
25039 [10038] Socket operation on non-socket. | |
25040 [10039] Destination address required. | |
25041 [10040] Message too long. | |
25042 [10041] Protocol wrong type for socket. | |
25043 [10042] Bad protocol option. | |
25044 [10043] Protocol not supported. | |
25045 [10044] Socket type not supported. | |
25046 [10045] Operation not supported on socket. | |
25047 [10046] Protocol family not supported. | |
25048 [10047] Address family not supported by protocol family. | |
25049 [10048] Address already in use. | |
25050 [10049] Can't assign requested address. | |
25051 [10050] Network is down. | |
25052 [10051] Network is unreachable. | |
25053 [10052] Net dropped connection or reset. | |
25054 [10053] Software caused connection abort. | |
25055 [10054] Connection reset by peer. | |
25056 [10055] No buffer space available. | |
25057 [10056] Socket is already connected. | |
25058 [10057] Socket is not connected. | |
25059 [10058] Can't send after socket shutdown. | |
25060 [10059] Too many references, can't splice. | |
25061 [10060] Connection timed out. | |
25062 [10061] Connection refused. | |
25063 [10062] Too many levels of symbolic links. | |
25064 [10063] File name too long. | |
25065 [10064] Host is down. | |
25066 [10065] No route to host. | |
25067 [10066] Directory not empty | |
25068 [10067] Too many processes. | |
25069 [10068] Too many users. | |
25070 [10069] Disc Quota Exceeded. | |
25071 [10070] Stale NFS file handle. | |
25072 [10071] Too many levels of remote in path. | |
25092 [10091] Network subsystem is unavailable. | |
25093 [10092] WINSOCK DLL Version out of range. | |
25094 [10093] Winsock not loaded yet. | |
26002 [11001] Host not found. | |
26003 [11002] Non-authoritative 'Host not found' (try again or check DNS setup). | |
26004 [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP. | |
26005 [11004] Valid name, no data record (check DNS setup). |