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DNS Sample Code

This page demonstrates how to perform DNS queries using the Windows DnsQuery API in C++. The sample includes both IPv4 and IPv6 lookups, error handling, and resource cleanup.

Prerequisites

Sample Code (C++)

#include <windows.h>
#include <winldap.h>
#include <windns.h>
#include <iostream>
#include <vector>
#include <string>

#pragma comment(lib, "dnsapi.lib")

void PrintDnsRecord(PDNS_RECORD record) {
    while (record) {
        std::wcout << L"Record Type: " << record->wType << L"\\n";
        if (record->Data.A) {
            std::wcout << L"IPv4: " << record->Data.A->IpAddress << L"\\n";
        } else if (record->Data.AAAA) {
            wchar_t ip[INET6_ADDRSTRLEN];
            inet_ntop(AF_INET6, &record->Data.AAAA->Ip6Address, ip, sizeof(ip));
            std::wcout << L"IPv6: " << ip << L"\\n";
        } else if (record->Data.PTR) {
            std::wcout << L"PTR: " << record->Data.PTR->pNameHost << L"\\n";
        }
        record = record->pNext;
    }
}

int main() {
    const wchar_t* hostname = L"example.com";
    PDNS_RECORD result = nullptr;
    DNS_STATUS status = DnsQuery_W(hostname,
                                   DNS_TYPE_A,
                                   DNS_QUERY_BYPASS_CACHE,
                                   nullptr,
                                   &result,
                                   nullptr);
    if (status != 0) {
        std::wcerr << L"DnsQuery failed: " << status << L"\\n";
        return 1;
    }

    std::wcout << L"Results for " << hostname << L":\\n";
    PrintDnsRecord(result);
    DnsRecordListFree(result, DnsFreeRecordList);
    return 0;
}

Run the Sample

  1. Save the code above as DnsLookup.cpp.
  2. Open a Developer Command Prompt for Visual Studio.
  3. Compile: 
    cl /EHsc DnsLookup.cpp /link dnsapi.lib
  4. Execute: 
    DnsLookup.exe

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