Internet Direct (Indy) Version 9.0.2 Beta
TDNSHeader.OpCode
Indicates the kind of query to be performed on the DNS server.

property OpCode: Word;
Description
OpCode is a Word property and contains an Integer value that specifies the kind of query in a DNS request packet. OpCode is specified in the DNS query, and returned in the DNS response. OpCode may contain one of the follwing values and meanings:

Note: Currently, the TIdDNSResolver implementation does not support all aspects of the DNS protocol, and includes the following limitations:

OpCode is represented in a DNS header as a 4-bit field. Changing the value of OpCode insures that the appropriate bit field is updated in the DNS header for the message packet.