IP Helper API – Windows Network Management

Overview

The IP Helper (IP Helper API) provides a set of functions that enable applications to retrieve and modify network configuration settings, query interface and routing information, and manage network interfaces on Windows operating systems.

Common Functions

Function	Header	Description
`GetAdaptersInfo`	iphlpapi.h	Retrieves adapter information.
`GetIfTable`	iphlpapi.h	Gets a table of network interfaces.
`GetIpAddrTable`	iphlpapi.h	Retrieves IPv4 address table.
`GetIpForwardTable`	iphlpapi.h	Retrieves IPv4 routing table.
`NotifyIpInterfaceChange`	iphlpapi.h	Registers for notification of interface changes.
`SetIfEntry`	iphlpapi.h	Modifies a network interface.

For a full list, see the Functions page.

Sample Code

Retrieve IPv4 address table and display each entry:

#include <windows.h>
#include <iphlpapi.h>
#include <stdio.h>
#pragma comment(lib, "iphlpapi.lib")

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

    pIPAddrTable = (MIB_IPADDRTABLE *) malloc(sizeof (MIB_IPADDRTABLE));
    if (pIPAddrTable) {
        dwSize = sizeof (MIB_IPADDRTABLE);
        if (GetIpAddrTable(pIPAddrTable, &dwSize, 0) == ERROR_INSUFFICIENT_BUFFER) {
            free(pIPAddrTable);
            pIPAddrTable = (MIB_IPADDRTABLE *) malloc(dwSize);
        }
        if (pIPAddrTable == NULL) {
            printf("Memory allocation error\\n");
            return 1;
        }
    }

    if ((dwRetVal = GetIpAddrTable(pIPAddrTable, &dwSize, 0)) == NO_ERROR) {
        printf("IPv4 Address Table:\\n");
        for (int i = 0; i < (int)pIPAddrTable->dwNumEntries; i++) {
            MIB_IPADDRROW row = pIPAddrTable->table[i];
            struct in_addr IpAddr;
            IpAddr.S_un.S_addr = (u_long) row.dwAddr;
            printf("Index:%d   Addr:%s   Mask:%s\\n",
                   row.dwIndex,
                   inet_ntoa(IpAddr),
                   inet_ntoa(*(struct in_addr *)&row.dwMask));
        }
    } else {
        printf("GetIpAddrTable failed with error: %d\\n", dwRetVal);
    }

    if (pIPAddrTable) free(pIPAddrTable);
    return 0;
}

Full examples are available on the Code Samples page.