TWKSRecord

Hierarchy, Properties, Methods, Unit: IdDNSResolver

Represents a Well Known Service Resource Record from a DNS Response packet.

TWKSRecord = class(TResultRecord)

Unit

IdDNSResolver

Description

TWKSRecord is a TResultRecord descendant that represents a resource record returned in the results for a DNS query. TWKSRecord is the collection item created to represent a resource resource returned when TIdDNSResolver.QueryRecords includes the value qtWKS for Well Known Service resource records.

Well Known Service resoure records are used to describe the well known services supported by a particular protocol on a particular internet address. If a server supports both TCP and UDP variants of a service, multiple WKS resource records are returned in a DNS response.

A Well Known Service resoure record uses the same DNS packet layout as other TResultRecord-based responses, but extends the use of RData to include the following definition and format:

  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |                    ADDRESS                    |
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  |       PROTOCOL        |                       |
  +--+--+--+--+--+--+--+--+                       |
  |                                               |
  .                                               .
  .                    BIT MAP                    .
  .                                               .
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

ADDRESS - 32-bit Internet address.
PROTOCOL - 8-bit IP protocol number. Uses BITMAP to indicate one bit per port of the specified protocol.
BITMAP - Variable length bit map with a length that is a multiple of 8- bits long. The first bit corresponds to port 0, the second to port 1, etc. If the bit map does not include a bit for a protocol of interest, that bit is assumed zero.

TWKSRecord extends TResultRecord to implement the specifics of accessing RData values as properties, including Address, Protocol, ByteCount, and BitMap. TWKSRecord also overrides the Parse method to read the values in RData into their property counterparts.

The appropriate values and mnemonics for ports and protocols are specified in RFC 1010. For example, if PROTOCOL=TCP, the 26th bit corresponds to TCP port 25 (SMTP). If this bit is set, a SMTP server should be listening on TCP port 25; if zero, SMTP service is not supported on the specified address.

Protocol specifies the IP protocol the host supports, as described in RFC 1010, and may contain one of the following values:

0 - Reserved
1 - ICMP Internet Control Message
2 - IGMP Internet Group Management
3 - GGP Gateway-to-Gateway
4 - Unassigned
5 - ST Stream
6 - TCP Transmission Control
7 - UCL
8 - EGP Exterior Gateway Protocol
9 - IGP any private interior gateway
10 - BBN-RCC-MON BBN RCC Monitoring
11 - NVP-II Network Voice Protocol
12 - PUP
13 - ARGUS
14 - EMCON
15 - XNET Cross Net Debugger
16 - CHAOS
17 - UDP User Datagram
18 - MUX Multiplexing
19 - DCN-MEAS DCN Measurement Subsystems
20 - HMP Host Monitoring
21 - PRM Packet Radio Measurement
22 - XNS-IDP XEROX NS IDP
23 - TRUNK-1 Trunk-1
24 - TRUNK-2 Trunk-2
25 - LEAF-1 Leaf-1
26 - LEAF-2 Leaf-2
27 - RDP Reliable Data Protocol
28 - IRTP Internet Reliable Transaction
29 - ISO-TP4 ISO Transport Protocol Class 4
30 - NETBLT Bulk Data Transfer Protocol
31 - MFE-NSP MFE Network Services Protocol
32 - MERIT-INP MERIT Internodal Protocol
33 - SEP Sequential Exchange Protocol
34 though 60 - Unassigned
61 - any host internal protocol
62 - CFTP
63 - any local network
64 - SAT-EXPAK SATNET and Backroom EXPAK
65 - MIT-SUBNET MIT Subnet Support
66 - RVD MIT Remote Virtual Disk Protocol
67 - IPPC Internet Pluribus Packet Core
68 - any distributed file system
69 - SAT-MON SATNET Monitoring
70 - Unassigned
71 - IPCV Internet Packet Core Utility
72 through 75 - Unassigned
76 - BR-SAT-MON Backroom SATNET Monitoring
77 - Unassigned
78 - WB-MON WIDEBAND Monitoring
79 - WB-EXPAK WIDEBAND EXPAK
80 through 254 - Unassigned
255 - Reserved

TWKSRecord.Address

TWKSRecord, See Also

IP Address for the Well Known Service Host.

property Address: String;

Description

Address is a Cardinal property that represents the 32-bit IP address for the host implementing the Protocol for the Well Known Service. Use Protocol and Bitmap to access the protocol or implemented features for the Well Known Service.

TWKSRecord.BitMap

TWKSRecord

Represents bits that indicate port usage for the Well Known Service.

property BitMap [index: integer]: Byte;

Description

BitMap is a read-only Byte property that provides indexed access to the port numbers used on the Host at the specified Address. BitMap is a variable length storage area that can be accessed using a zero-based index into the individual bits used to signify the port numbers allowed for the Protocol of the Well Known Service.

The appropriate values and mnemonics for ports numbers are specified in RFC 1010. For example, if Protocol is the value for TCP, the 26th bit corresponds to TCP port 25 (SMTP). If this bit is set, a SMTP server should be listening on TCP port 25; if zero, SMTP service is not supported on the specified address.

TWKSRecord.ByteCount

TWKSRecord, See Also

ByteCount is not currently used in TWKSRecord.

property ByteCount: integer;

Description

ByteCount is not currently used in TWKSRecord. ByteCount is not currently used in TWKSRecord. ByteCount is not currently used in TWKSRecord. ByteCount is not currently used in TWKSRecord.

TWKSRecord.Protocol

TWKSRecord

Protocol for the Well Known Service host.

property Protocol: Word;

Description

Protocol is a read-only Byte property that specifies the IP protocol supported for the Well Know Service host. Protocol can be one of the following values:

0 Reserved
1 ICMP Internet Control Message
2 IGMP Internet Group Management
3 GGP Gateway-to-Gateway
4 Unassigned
5 ST Stream
6 TCP Transmission Control
7 UCL UCL
8 EGP Exterior Gateway Protocol
9 IGP any private interior gateway
10 BBN-RCC-MON BBN RCC Monitoring
11 NVP-II Network Voice Protocol
12 PUP PUP
13 ARGUS ARGUS
14 EMCON EMCON
15 XNET Cross Net Debugger
16 CHAOS Chaos
17 UDP User Datagram
18 MUX Multiplexing
19 DCN-MEAS DCN Measurement Subsystems
20 HMP Host Monitoring
21 PRM Packet Radio Measurement
22 XNS-IDP XEROX NS IDP
23 TRUNK-1 Trunk-1
24 TRUNK-2 Trunk-2
25 LEAF-1 Leaf-1
26 LEAF-2 Leaf-2
27 RDP Reliable Data Protocol
28 IRTP Internet Reliable Transaction
29 ISO-TP4 ISO Transport Protocol Class 4
30 NETBLT Bulk Data Transfer Protocol
31 MFE-NSP MFE Network Services Protocol
32 MERIT-INP MERIT Internodal Protocol
33 SEP Sequential Exchange Protocol
34-60 Unassigned
61 any host internal protocol
62 CFTP CFTP
63 any local network
64 SAT-EXPAK SATNET and Backroom EXPAK
65 MIT-SUBNET MIT Subnet Support
66 RVD MIT Remote Virtual Disk Protocol
67 IPPC Internet Pluribus Packet Core
68 any distributed file system
69 SAT-MON SATNET Monitoring
70 Unassigned
71 IPCV Internet Packet Core Utility
72-75 Unassigned
76 BR-SAT-MON Backroom SATNET Monitoring
77 Unassigned
78 WB-MON WIDEBAND Monitoring
79 WB-EXPAK WIDEBAND EXPAK
80-254 Unassigned
255 Reserved

TWKSRecord.Create

TWKSRecord

Constructor for the object instance.

constructor Create(Collection: TCollection); override;

Parameters

Collection: TCollection

Owner of the collection item.

Description

Create is the constructor for the object instance. Create calls the inherited Create method using Collection as the owner of the collection item.

TWKSRecord.Destroy

TWKSRecord, See Also

Frees the resource record collection item.

destructor Destroy; override;

Description

Destroy is the destructor for the object instance. Destroy calls the inherited Destroy method prior to exiting.

TWKSRecord.Parse

TWKSRecord

Parses RData values into properties.

procedure Parse(CompleteMessage: String; APos: Integer); override;

Parameters

CompleteMessage: String

Contents of the resource record.

APos: Integer

Position where RData values begin in the answer.

Description

Parse is an overridden procedure that implements a routine to parse resource record values in the DNS response into their property-based counterparts.

CompleteMessage is the contents of the resource record. Since the DNS message can contain compressed data, the whole message is needed for parsing and pointer location.

APos is the position in the resource record where RData values for this record type are located in the DNS Answer.

Parse calls the inherited Parse method, and retrieves the DNS labels and values for the Address, Protocol, ByteCount, and BitMap properties.

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