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Description
Ultibo DNS client unit
Note: DNS Client is IPv4 based, for IPv6 see new Winsock2 functions
See RFC 1035 Section 4 for details
Constants
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DNS specific constants DNS_*
DNS_TIMEOUT = 5000;
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We wait for 5 seconds for a DNS reply
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DNS_RETRIES = 4;
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Try the request 4 times
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DNS_HEADER_SIZE = 12;
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SizeOf(TDNSHeader);
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DNS_QUESTION_SIZE = 4;
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SizeOf(TDNSQuestion);
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DNS_RESOURCE_SIZE = 10;
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SizeOf(TDNSResource); Not including Record Data
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MAX_DNS_NAME = 255;
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MAX_DNS_LABEL = 63;
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MAX_DNS_MESSAGE = 512;
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Maximum Size of DNS Message
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DNS flag DNS_FLAG_*
DNS_FLAG_RESPONSE = $8000;
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query = 0, response = 1
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DNS_FLAG_AUTHORITY = $0400;
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Authoritative answer
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DNS_FLAG_TRUNCATED = $0200;
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Truncation, response was cut off at 512
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DNS_FLAG_DO_RECURSE = $0100;
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Recursion desired
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DNS_FLAG_CAN_RECURSE = $0080;
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Recursion available
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[Expand]
DNS field masks DNS_OPCODE_*
DNS_OPCODE_MASK = $7800;
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Opcode
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DNS_RESPONSE_MASK = $000F;
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Response code
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[Expand]
DNS query code DNS_QUERY*
DNS_QUERY = 0;
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A standard query
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DNS_INV_QUERY = 1;
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An inverse query
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DNS_COMP_QUERY_MULTI = 2;
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A completion query, multiple reply (Obsolete)
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DNS_COMP_QUERY_SINGLE = 3;
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A completion query, single reply (Obsolete)
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[Expand]
DNS response code DNS_NO_*
DNS_NO_ERROR = 0;
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DNS_FORMAT_ERROR = 1;
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DNS_SERVER_FAILURE = 2;
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DNS_NAME_ERROR = 3;
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DNS_NOT_IMPLEMENTED = 4;
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DNS_REFUSED = 5;
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[Expand]
DNS record type DNS_TYPE_*
DNS_TYPE_A = 1;
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Host address resource record (RR)
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DNS_TYPE_NS = 2;
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DNS_TYPE_MD = 3;
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DNS_TYPE_MF = 4;
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DNS_TYPE_CNAME = 5;
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DNS_TYPE_SOA = 6;
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DNS_TYPE_MB = 7;
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DNS_TYPE_MG = 8;
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DNS_TYPE_MR = 9;
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DNS_TYPE_RT_NULL = 10;
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DNS_TYPE_WKS = 11;
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DNS_TYPE_PTR = 12;
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A domain name ptr
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DNS_TYPE_HINFO = 13;
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DNS_TYPE_MINFO = 14;
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DNS_TYPE_MX = 15;
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Mail exchange
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[Expand]
DNS address class DNS_CLASS_*
DNS_CLASS_IN = 1;
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ARPA internet class
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DNS_CLASS_CS = 2;
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DNS_CLASS_WILD = 255;
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Wildcard for several of the classifications
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[Expand]
DNS message compression DNS_POINTER_*
DNS_POINTER_MASK = $C0;
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Mask to indicate pointer to previously used name
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Type definitions
DNS specific types
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PDNSHeader = ^TDNSHeader;
TDNSHeader = packed record
| Note: All Network Order
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Identifier:Word;
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unique identifier
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Flags:Word;
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QD/Opcode/AA/TC/RD/RA/RCODE
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QuestionCount:Word;
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question section, number of entries
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AnswerCount:Word;
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answers, how many
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AuthorityCount:Word;
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count of name server RRs
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AdditionalCount:Word;
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number of "additional" records
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DNS message
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PDNSMessage = ^TDNSMessage;
TDNSMessage = packed record
DNS:TDNSHeader;
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Data:array[0..(MAX_DNS_MESSAGE - DNS_HEADER_SIZE) - 1] of Byte;
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DNA name
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PDNSName = ^TDNSName;
TDNSName = array[0..MAX_DNS_NAME - 1] of Char;
DNS question
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PDNSQuestion = ^TDNSQuestion;
TDNSQuestion = packed record
| Note: All Network Order
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Name:TDNSName;
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variable length question name
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QuestionType:Word;
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question type (eg DNS_TYPE_A)
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QuestionClass:Word;
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question class (eg DNS_CLASS_IN)
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DNS resource
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PDNSResource = ^TDNSResource;
TDNSResource = packed record
| Note: All Network Order
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Name:TDNSName;
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variable length resource name
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RecordType:Word;
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resource record type (eg DNS_TYPE_A)
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RecordClass:Word;
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resource record class (eg DNS_CLASS_IN)
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Ttl:LongWord;
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time-to-live, changed to 32 bits
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DataLength:Word;
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length of data field
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RecordData:array[0..MAX_DNS_MESSAGE - 1] of Byte;
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data field
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DNA client data
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PDNSClientData = ^TDNSClientData;
TDNSClientData = record
| Note: Used for TLS Data
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| Host Ent
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HostEnt:THostEnt;
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HostEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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HostAliasesPtr:PChar;
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HostAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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HostAddrListPtr:PChar;
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HostAddrList:array[0..MAX_HOST_ALIASES - 1] of TInAddr;
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| Net Ent
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NetEnt:TNetEnt;
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NetEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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NetAliasesPtr:PChar;
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NetAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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| Serv Ent
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ServEnt:TServEnt;
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ServEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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ServAliasesPtr:PChar;
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ServAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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ServEntProto:array[0..MAX_NAME_SIZE - 1] of Char;
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| Proto Ent
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ProtoEnt:TProtoEnt;
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ProtoEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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ProtoAliasesPtr:PChar;
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ProtoAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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Class definitions
DNS client
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TDNSClient = class(TNetworkClient)
constructor Create(AProtocol:TNetworkProtocol);
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destructor Destroy; override;
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private
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FTlsIndex:LongWord;
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function GetClientData:PDNSClientData;
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function CreateClientData:Boolean;
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function AddressEntryToHostEnt(AddressEntry:TIPAddressEntry; const AName:String; ACount:Integer):PHostEnt;
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function HostEntryToHostEnt(HostEntry:TIPHostEntry):PHostEnt;
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function NetworkEntryToNetEnt(NetworkEntry:TIPNetworkEntry):PNetEnt;
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function ServEntryToServEnt(ServEntry:TIPServEntry):PServEnt;
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function ProtoEntryToProtoEnt(ProtoEntry:TIPProtoEntry):PProtoEnt;
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function InAddrToName(const AAddress:TInAddr):String;
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function NameToInAddr(const AName:String):TInAddr;
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function In6AddrToName(const AAddress:TIn6Addr):String;
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function NameToIn6Addr(const AName:String):TIn6Addr;
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function GetDNSMessageSize(AMessage:PDNSMessage):Integer;
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function GetDNSNameSize(AMessage:PDNSMessage; AOffset:Word):Word;
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function GetDNSQuestionSize(AMessage:PDNSMessage; AOffset:Word):Word;
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function GetDNSResourceSize(AMessage:PDNSMessage; AOffset:Word):Word;
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function GetDNSQuestionOffset(AMessage:PDNSMessage; ACount:Word):Word;
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function GetDNSAnswerOffset(AMessage:PDNSMessage; ACount:Word):Word;
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function GetDNSAuthorityOffset(AMessage:PDNSMessage; ACount:Word):Word;
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function GetDNSAdditionalOffset(AMessage:PDNSMessage; ACount:Word):Word;
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function CreateDNSQuery(AMessage:PDNSMessage; AIdentifier:Word):Boolean;
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function CheckDNSResponse(AMessage:PDNSMessage; AIdentifier:Word):Boolean;
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function HandleDNSResponse(AMessage:PDNSMessage; AIdentifier:Word):Boolean;
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function SendDNSQuery(ASocket:TProtocolSocket; const AServer:TInAddr; AData:Pointer; ALength,AType,AClass,AIdentifier:Word):Boolean;
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function RecvDNSResponse(ASocket:TProtocolSocket; AType,AClass,AIdentifier:Word):Boolean;
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function InsertDNSName(AMessage:PDNSMessage; AOffset:Word; AName:Pointer; ALength:Word):Boolean;
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function ExtractDNSName(AMessage:PDNSMessage; AOffset:Word; AName:Pointer; var ALength:Word):Boolean;
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function ExtractDNSRData(AMessage:PDNSMessage; AOffset:Word; AData:Pointer; var ALength:Word; AType,AClass:Word):Boolean;
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function InsertDNSQuestion(AMessage:PDNSMessage; ACount:Word; AData:Pointer; ALength,AType,AClass:Word):Boolean;
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function ExtractDNSAnswer(AMessage:PDNSMessage; ACount:Word; AName,AData:Pointer; var ANameLength,ADataLength,AType,AClass:Word; var ATtl:LongWord):Boolean;
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function ExtractDNSAuthority(AMessage:PDNSMessage; ACount:Word; AName,AData:Pointer; var ANameLength,ADataLength,AType,AClass:Word; var ATtl:LongWord):Boolean;
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function ExtractDNSAdditional(AMessage:PDNSMessage; ACount:Word; AName,AData:Pointer; var ANameLength,ADataLength,AType,AClass:Word; var ATtl:LongWord):Boolean;
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public
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function GetHostByAddr(AAddr:Pointer; ALength,AFamily:Integer):PHostEnt;
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function GetHostByName(AName:PChar):PHostEnt;
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function GetHostName(AName:PChar; ALength:Integer):Integer;
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function GetServByPort(APort:Integer; AProto:PChar):PServEnt;
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function GetServByName(AName,AProto:PChar):PServEnt;
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function GetProtoByNumber(AProto:Integer):PProtoEnt;
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function GetProtoByName(AName:PChar):PProtoEnt;
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function GetNetByAddr(AAddr:Pointer; ALength,AStruct:Integer):PNetEnt;
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function GetNetByName(AName:PChar):PNetEnt;
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function StartClient:Boolean; override;
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function StopClient:Boolean; override;
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Public variables
None defined
Function declarations
Initialization functions
[Expand]
procedure DNSInit;
Description: To be documented
[Expand]
function DNSStart:LongWord;
Description: To be documented
[Expand]
function DNSStop:LongWord;
Description: To be documented
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