Topic Path: Symbol Reference > Classes > TDNSHeader Class
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TDNSHeader Class

Represents the Header section in a DNS message packet.

File
TDNSHeader = class;

TDNSHeader is a TObject descendant that represents the Header section in a DNS message packet. A DNS message packet may contain the following 5 sections: 

 

 

Section 
Description 
Header 
 
Question 
question for the name server 
Answer 
resource records answering the question 
Authority 
resource records pointing toward an authority 
Additional 
resource records holding additional information 

 

The TDNSHeader header section is always present in the message packet, and includes values that specify which of the remaining sections are present. TDNSHeader also provides properties specific to the header section or the entire message packet, including: 

 

 

Field 
Description 
ID 
Identifier assigned to a DNS query. 
Qr 
Query (0) or Response (1) flag. 
Indicates the kind of query to be performed. 
AA 
Indicates the responsing DNS server is an authority for the domain. 
TC 
Indicates the message was truncated. 
RD 
Indicates recurive queries are desired on the DNS server. 
RA 
Indicates recurive queries are available on the DNS server. 
Response code from the DNS server. 
Number of entries in the DNS Question section. 
Number of resource records in the DNS Answer section. 
Number of resource records in the DNS Authority section. 
Number of resource records in the DNS Additional section. 

 

TDNSHeader is used in the message packet for both a DNS query and a DNS response, although some values are only appropriate in one or the other context.

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