Getting DNS information

Sample code

The following sample code shows how to use GetNetworkParams().

#include <stdio.h>

#include <winsock2.h>
#include <iphlpapi.h>

int
main()
{
 FIXED_INFO *FixedInfo = NULL;
 ULONG    ulOutBufLen = 0;
 DWORD    dwRetVal;
 IP_ADDR_STRING *pIPAddr;
   
 if(GetNetworkParams(NULL, &ulOutBufLen) == ERROR_BUFFER_OVERFLOW) {
   FixedInfo = (FIXED_INFO *)GlobalAlloc(GPTR, ulOutBufLen);
 } else {
   return 1;
 }

 if (dwRetVal = GetNetworkParams(FixedInfo, &ulOutBufLen)) {
   printf("GetNetworkParams() failed: %08x\n", dwRetVal);
   return 1;
 } else {
   printf("Host Name: %s\n", FixedInfo->HostName);
   printf("Domain Name: %s\n", FixedInfo->DomainName);

   printf("DNS Servers:\n" );
   printf("\t%s\n", FixedInfo->DnsServerList.IpAddress.String);
      
   pIPAddr = FixedInfo->DnsServerList.Next;
   while (pIPAddr ) {
     printf("\t%s\n", pIPAddr->IpAddress.String);
     pIPAddr = pIPAddr->Next;
   }
 }

 return 0;
}

Sample code output

The sample will output an message like the following.

C:> a.exe
Host Name: GeekPC
Domain Name:
DNS Server:
      192.168.0.1

Structure used by GetNetworkParams()

The following structure is FIXED_INFO that is used by GetNetworkParams().

typedef struct {
  char HostName[MAX_HOSTNAME_LEN + 4];
  char DomainName[MAX_DOMAIN_NAME_LEN + 4];
  PIP_ADDR_STRING CurrentDnsServer;
  IP_ADDR_STRING DnsServerList;
  UINT NodeType;
  char ScopeId[MAX_SCOPE_ID_LEN + 4];
  UINT EnableRouting;
  UINT EnableProxy;
  UINT EnableDns;
} FIXED_INFO, *PFIXED_INFO;

HostName	Host name of the local computer.
DomainName	The domain that the local computer is in.
CurrentDnsServer	Not used. It seems that DnsServerList is used instead.
DnsServerList	List of DNS servers used by the local computer. It is a linked list.
NodeType	Node type of the local computer. Following 4 types are available, BROADCAST_NODETYPE, PEER_TO_PEER_NODETYPE, MIXED_NODETYPE, HYBRID_NODETYPE.
ScopeId	DHCP scope name.
EnableRouting	Shows if routing is enabled. i.e. Shows if the local computer is a router.
EnableProxy	Shows if the local computer serves an ARP Proxy service.
EnableDns	Shows if the local computer serves as a DNS server.