获得本地IP

//一些定义：
// hostent declare
/*struct  hostent {
        char    FAR * h_name;           // official name of host
        char    FAR * FAR * h_aliases;  // alias list
        short   h_addrtype;             // host address type
        short   h_length;               // length of address
        char    FAR * FAR * h_addr_list; // list of addresses
#define h_addr  h_addr_list[0]          // address, for backward compat
};

struct in_addr {
        union {
                struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
                struct { u_short s_w1,s_w2; } S_un_w;
                u_long S_addr;
        } S_un;

#define s_addr  S_un.S_addr  // can be used for most tcp & ip code
#define s_host  S_un.S_un_b.s_b2 // host on imp
#define s_net   S_un.S_un_b.s_b1        // network
#define s_imp   S_un.S_un_w.s_w2 // imp
#define s_impno S_un.S_un_b.s_b4 // imp #
#define s_lh    S_un.S_un_b.s_b3 // logical host
};

//sockaddr delcare
struct sockaddr {
        u_short sa_family;              // address family
        char    sa_data[14];            // up to 14 bytes of direct address
};

//sockaddr_in declare
struct sockaddr_in {
        short   sin_family;
        u_short sin_port;
        struct  in_addr sin_addr;
        char    sin_zero[8];
};*/

#include <winsock2.h>
#include "CInitSock.h"
#include <iostream>
#include <stdio.h>

using namespace std;

#pragma comment(lib, "WS2_32")

int const MAX_SIZE = 256;

class CInitSock
{
public:
 CInitSock(BYTE minorVer = 2, BYTE majorVer = 2)
 {
  WSADATA wsaData;
  WORD sockVersion = MAKEWORD(minorVer, majorVer);

  if (::WSAStartup(sockVersion, &wsaData) != 0)
  {
   exit(0);
  }
 }

 ~CInitSock()
 {
  ::WSACleanup();
 }
};

CInitSock initSock(1, 1);

int main()
{
 char szHost[MAX_SIZE] = "/0";
 hostent* pHost = NULL;
 in_addr addr = {0};

 int i = 0;

 ::gethostname(szHost, MAX_SIZE);
 pHost = ::gethostbyname(szHost);

 for (i = 0; ; i++)
 {
  char* p = pHost->h_addr_list[i];

  if (p == NULL)
  {
   break;
  }

  memcpy(&addr.S_un.S_addr, p, pHost->h_length);

  char* szIP = ::inet_ntoa(addr);

  cout << "local ip address: " << szIP << endl;
 } 

}