C++利用SIO_GET_INTERFACE_LIST查詢網關

  本文提供利用SIO_GET_INTERFACE_LIST實現本地網關查詢的簡單工具代碼。

#include <iostream>
#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>

// Need to link with Ws2_32.lib
#pragma comment(lib, "ws2_32.lib")

using namespace std;

int doit()
{
	//創建套接字
    SOCKET sd = WSASocket(AF_INET, SOCK_DGRAM, 0, 0, 0, 0);
    if (sd == SOCKET_ERROR) {
        cerr << "Failed to get a socket. Error " << WSAGetLastError() <<
            endl; return 1;
    }

	//獲取網關信息，保存在InterfancList中
    INTERFACE_INFO InterfaceList[20];
    unsigned long nBytesReturned;
    if (WSAIoctl(sd, SIO_GET_INTERFACE_LIST, 0, 0, &InterfaceList,
        sizeof(InterfaceList), &nBytesReturned, 0, 0) == SOCKET_ERROR) {
        cerr << "Failed calling WSAIoctl: error " << WSAGetLastError() <<
            endl;
        return 1;
    }

	//輪詢讀取信息並打印
    int nNumInterfaces = nBytesReturned / sizeof(INTERFACE_INFO);
    cout << "There are " << nNumInterfaces << " interfaces:" << endl;
    for (int i = 0; i < nNumInterfaces; ++i) {
        cout << endl;

        char sendBuf[20] = { '\0' };
        sockaddr_in *pAddress;
        pAddress = (sockaddr_in *)&(InterfaceList[i].iiAddress);
        cout << " " << inet_ntop(AF_INET, &pAddress->sin_addr, sendBuf, 16) << endl;

        pAddress = (sockaddr_in *)&(InterfaceList[i].iiBroadcastAddress);
        cout << " has bcast " << inet_ntop(AF_INET, &pAddress->sin_addr, sendBuf, 16) << endl;

        pAddress = (sockaddr_in *)&(InterfaceList[i].iiNetmask);
        cout << " and netmask " << inet_ntop(AF_INET, &pAddress->sin_addr, sendBuf, 16) << endl;

        cout << " Iface is ";

        u_long nFlags = InterfaceList[i].iiFlags;
        if (nFlags & IFF_UP) 
            cout << "up";
        else                 
            cout << "down";

        if (nFlags & IFF_POINTTOPOINT) 
            cout << ", is point-to-point";

        if (nFlags & IFF_LOOPBACK)     
            cout << ", is a loopback iface";

        cout << ", and can do: ";

        if (nFlags & IFF_BROADCAST) 
            cout << "bcast ";

        if (nFlags & IFF_MULTICAST) 
            cout << "multicast ";

        cout << endl;
    }

    return 0;
}

int main()
{
    WSADATA WinsockData;
    if (WSAStartup(MAKEWORD(2, 2), &WinsockData) != 0) {
        cerr << "Failed to find Winsock 2.2!" << endl;
        return 2;
    }

    int nRetVal = doit();

    WSACleanup();

    return nRetVal;
}