c:
# include <windows.h>
# include <urlmon.h>
# pragma comment(lib,"URLMON.lib")
void main()
{
    URLDownloadToFile(NULL,"http://www.ip138.com/ip2city.asp","ip.txt",0,NULL);
    system("notepad ip.txt");
}

#include<urlmon.h>
#pragma comment (lib,"Urlmon.lib")


char buf[MAX_PATH] = {0};
    char chTempIp[128];
    char chIP[64];
    URLDownloadToFile(0,"http://www.ip138.com/ip2city.asp","c:\\1.ini",0,NULL);
 
    FILE *fp=fopen( "c:\\1.ini", "r" );
    
    if ( fp != NULL ) 
    {
  
        fseek(fp, 0, SEEK_SET);
        fread(buf,1,256,fp);
        fclose(fp);
        char* iIndex = strstr(buf,"[");
  
        if (iIndex) 
          {
             sprintf( chTempIp,"%s",iIndex);
             int nBuflen = strlen(chTempIp);
   
      for(int i =0; i<nBuflen; i++)
              {
                chIP[i] = chTempIp[i+1];
    
                if(chTempIp[i] == ']') 
                 {
      chIP[i-1] = '\0';
                    DeleteFile("c:\\1.ini");
                    continue;
                 }
                
              }
  }
        
   }
    MessageBox(chIP);

 

MFC:
#include <afxinet.h>
void CLanChatDlg::GetNetIP()
{
 
 SetDlgItemText(IDC_NET_IP,"正在获取外网IP");
 CString strsource;
 CString Address;
 CInternetSession mySession(NULL,0);
 CHttpFile* myHttpFile=NULL;
 
 Address="http://www.ip138.com/ip2city.asp";//ip138网页
 
 myHttpFile=(CHttpFile*)mySession.OpenURL(Address);//读取网络地址

 while(myHttpFile->ReadString(strsource))
 {  //循环读取下载来的网页文本
  //  AddToLog(strsource);
  int begin=0;
  begin=strsource.Find("[",0);
  
  if(begin!=-1)//如果找到"["， 则找"]"  中括号内的文本则是 你的外网ip
  { int end=strsource.Find("]");
  m_internetip=strsource.Mid(begin+1,end-begin-1);//提取外网ip
 
  SetDlgItemText(IDC_NET_IP,m_internetip);//在左下角显示外网ip
  }
 }

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