用VC++怎么判断某个url有效或者某个网址存在？

Question

就是去用VC去得到某个网址的返回值
比如：打开百度，可以访问，得到 http 200
      打开某个不存在的网址，得到 400的错误
      等等 

Answer 1

打开某个网址后, 获取http头部, 分析返回值

Answer 2

      // Connect to www.baidu.com.   
      HINTERNET hConnect = InternetConnect(hSession,
                                    "www.baidu.com",
                                    INTERNET_INVALID_PORT_NUMBER,
                                    "",
                                    "",
                                    INTERNET_SERVICE_HTTP,
                                    0,
                                    0);
      
      // Request the file /index.php from the server.
      HINTERNET hUrl = HttpOpenRequest(hConnect,
                                     "GET",
                                     "/index.php",
                                     HTTP_VERSION,
                                     NULL,
                                     0,
                                     INTERNET_FLAG_DONT_CACHE,
                                     0);      // Add request headers
      TCHAR szHeaders[] = "Accept: text/*\r\n";
      BOOL bAddHeaders = HttpAddRequestHeaders(hConnect,
                                  szHeaders,
                                  lstrlen(szHeaders),
                                  HTTP_ADDREQ_FLAG_ADD);      // Send the request.
      BOOL bSendRequest = HttpSendRequest(hUrl, NULL, 0, 0, 0);      if(hUrl == NULL)
      {
              printf("InternetOpenUrl Error......\n");
              InternetCloseHandle(hSession);
              return 0;
      }
      
      BOOL bRet = HttpQueryInfo(hUrl, HTTP_QUERY_STATUS_CODE|HTTP_QUERY_FLAG_NUMBER, &dwStatusCode, &dwSizeOfStatusCode, NULL);
      if(!bRet)
      {
             printf("HttpQueryInfo Error......\n");
             return 0;
      }
      
      // Key point
      if(404 == dwStatusCode)
      {
             InternetCloseHandle(hUrl) ;
             InternetCloseHandle(hSession) ;
             return 0;
      }