Getting IP information from network interface

Sample code

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

#include <stdio.h>

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

int
main()
{
 DWORD i;
 PMIB_IPADDRTABLE pIpAddrTable;
 DWORD dwSize = 0;
 DWORD dwRetVal = 0;

 /* Get size required by GetIpAddrTable() */
 if (GetIpAddrTable(NULL, &dwSize, 0) == ERROR_INSUFFICIENT_BUFFER) {
   pIpAddrTable = (MIB_IPADDRTABLE *) malloc (dwSize);
 }

 /* Get actual data using GetIpAddrTable() */
 if ((dwRetVal = GetIpAddrTable(pIpAddrTable, &dwSize, 0))
      == NO_ERROR) {
   if (pIpAddrTable->dwNumEntries > 0) {
     for (i=1; i<=pIpAddrTable->dwNumEntries; i++) {
       printf("Address: %s\n",
        inet_ntoa(*(struct in_addr *)&pIpAddrTable->table[i].dwAddr));
       printf("Mask:    %s\n",
        inet_ntoa(*(struct in_addr *)&pIpAddrTable->table[i].dwMask));
       printf("Index:   %ld\n", pIpAddrTable->table[i].dwIndex);
       printf("BCast:   %ld\n", pIpAddrTable->table[i].dwBCastAddr);
       printf("Reasm:   %ld\n", pIpAddrTable->table[i].dwReasmSize);
       printf("\n");
     }
   }
 } else {
   printf("GetIpAddrTable failed.\n");
   LPVOID lpMsgBuf;
			
   if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                     FORMAT_MESSAGE_FROM_SYSTEM | 
                     FORMAT_MESSAGE_IGNORE_INSERTS,
                     NULL,
                     dwRetVal,
                     MAKELANGID(LANG_NEUTRAL,
                                SUBLANG_DEFAULT), //Default language
                     (LPTSTR) &lpMsgBuf,
                     0,
                     NULL ))  {
                       printf("\tError: %s", lpMsgBuf);
   }

   LocalFree( lpMsgBuf );
 }

 return 0;
}

Sample code output

The sample will output an message like the following.

C:> a.exe
Address: 192.168.0.3
Mask:    255.255.255.0
Index:   2
BCast:   1
Reasm:   65535

Address: 127.0.0.1
Mask:    255.0.0.0
Index:   1
BCast:   1
Reasm:   65535

Structure used by GetIpAddrTable()

The following structure is MIB_IPADDRTABLE that is used by GetIpAddrTable().

typedef struct _MIB_IPADDRROW {
  DWORD dwAddr;
  DWORDIF_INDEX dwIndex;
  DWORD dwMask;
  DWORD dwBCastAddr;
  DWORD dwReasmSize;
  unsigned short unused1;
  unsigned short wType;
} MIB_IPADDRROW, *PMIB_IPADDRROW;

typedef struct _MIB_IPADDRTABLE {
  DWORD dwNumEntries;
  MIB_IPADDRROW table[ANY_SIZE];
} MIB_IPADDRTABLE, *PMIB_IPADDRTABLE;

MIB_IPADDRROW

MIB_IPADDRTABLE

Note

In WindowsXP platform, it is recommended to use GetAdaptersAddresses() rather than GetIpAddrTable(). GetAdaptersAddresses() supports both IPv4 and IPv6, while GetIpAddrTable() only supports IPv4. However, if you decide to use only IPv4, you can use GetIpAddrTable().