获取外网的IP地址

// GetIP.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <winsock2.h>
#include <WS2tcpip.h>

using namespace std;

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

int main(int argc, char **argv)
{ 
	char   *ptr, **pptr;
	struct hostent *hptr;
	char   str[32];
	int iResult;
	WSADATA WSAData;
	ptr = "www.baidu.com";
	iResult=WSAStartup(MAKEWORD(2, 0), &WSAData);
	if (iResult != 0) 
	{
		printf("WSAStartup failed: %d\n", iResult);
		WSACleanup();
		system("pause");
		return 1;
	}
	if((hptr = gethostbyname(ptr)) == NULL)
	{
		printf("gethostbyname error for host:%s\n", ptr);
		return 0;
	}
	printf("official hostname:%s\n",hptr->h_name);
	for(pptr = hptr->h_aliases; *pptr != NULL; pptr++)
		printf("alias:%s\n",*pptr);
	switch(hptr->h_addrtype)
	{
	case AF_INET:
	case AF_INET6:
		pptr=hptr->h_addr_list;
		for(; *pptr!=NULL; pptr++)
			printf("address:%s\n",
			inet_ntop(hptr->h_addrtype, *pptr, str, sizeof(str)));
		printf("first address: %s\n",
			inet_ntop(hptr->h_addrtype, hptr->h_addr, str, sizeof(str)));
		break;
	default:
		printf("unknown address type\n");
		break;
	}
	system("pause");
	return 0;
} 

执行结果：