使用C语言 判断当前网络是否联通

方式一：

 int GetNetStat( )
  {
     char    buffer[BUFSIZ];
     FILE    *read_fp;
     int        chars_read;
     int        ret;
     try
     {
      memset( buffer, , BUFSIZ );
      read_fp = popen("ifconfig eth0 | grep RUNNING", "r");
      if ( read_fp != NULL )
      {
          chars_read = fread(buffer, sizeof(char), BUFSIZ-, read_fp);
          if (chars_read > )
          {
              ret = ;
          }
          else
          {
              ret = -;
          }
          pclose(read_fp);
      }
      else
      {
          ret = -;
      }
      }
      catch
      {
         ret = -;
      }

     return ret;
  }

方式二：

 #define NET_PORT 53
 #define NET_IP "8.8.8.8" //谷歌DNS

 //获取联网状态
 int check_net(void)
 {

         int fd;
         int in_len=;
         struct sockaddr_in servaddr;
         //char buf[128];

         in_len = sizeof(struct sockaddr_in);
         fd = socket(AF_INET,SOCK_STREAM,);
         if(fd < )
         {
                 perror("socket");
                 return -;
         }   

         /*设置默认服务器的信息*/
         servaddr.sin_family = AF_INET;
         servaddr.sin_port = htons(NET_PORT);
         servaddr.sin_addr.s_addr = inet_addr(NET_IP);
         memset(servaddr.sin_zero,,sizeof(servaddr.sin_zero));

         /*connect 函数*/
         if(connect(fd,(struct sockaddr* )&servaddr,in_len) <  )
         {   

                 printf("not connect to internet!\n ");
                 close(fd);
                 return ; //没有联网成功
         }
         else
         {
                 printf("=====connect ok!=====\n");
                 close(fd);
                 return ;
         }
 }