How to get internal IP, external IP and default gateway for UPnP

I'm wondering how I'd go about getting the:

• Internal IP address;
• External IP address; and
• Default gateway

in Windows (WinSock) and Unix systems.

Thanks in advance,

Solved thanks to: http://www.codeguru.com/forum/showthread.php?t=233261

#include <winsock2.h>
#include <stdio.h>
#include <stdlib.h>

#pragma comment(lib, "ws2_32.lib")

int main(int nArgumentCount, char **ppArguments)
{
    WSADATA WSAData;

    // Initialize WinSock DLL
    if(WSAStartup(MAKEWORD(1, 0), &WSAData))
    {
        // Error handling
    }

    // Get local host name
    char szHostName[128] = "";

    if(gethostname(szHostName, sizeof(szHostName)))
    {
        // Error handling -> call 'WSAGetLastError()'
    }

    SOCKADDR_IN socketAddress;
    hostent *pHost        = 0;

    // Try to get the host ent
    pHost = gethostbyname(szHostName);
    if(!pHost)
    {
        // Error handling -> call 'WSAGetLastError()'
    }

    char ppszIPAddresses[10][16]; // maximum of ten IP addresses
    for(int iCnt = 0; (pHost->h_addr_list[iCnt]) && (iCnt < 10); ++iCnt)
    {
        memcpy(&socketAddress.sin_addr, pHost->h_addr_list[iCnt], pHost->h_length);
        strcpy(ppszIPAddresses[iCnt], inet_ntoa(socketAddress.sin_addr));

        printf("Found interface address: %s\n", ppszIPAddresses[iCnt]);
    }

    // Cleanup
    WSACleanup();
}