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, 0, BUFSIZ );
     read_fp = popen("ifconfig eth0 | grep RUNNING", "r");
     if ( read_fp != NULL ) 
     {
         chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
         if (chars_read > 0) 
         {
             ret = 1;
         }
         else
         {
             ret = -1;
         }
         pclose(read_fp);
     }
     else
     {
         ret = -1;
     }
     }
     catch
     {
        ret = -1;
     }
 
    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=0;
        struct sockaddr_in servaddr;
        //char buf[128];

        in_len = sizeof(struct sockaddr_in);
        fd = socket(AF_INET,SOCK_STREAM,0);
        if(fd < 0)
        {   
                perror("socket");
                return -1; 
        }   

        /*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,0,sizeof(servaddr.sin_zero));

        /*connect 函数*/
        if(connect(fd,(struct sockaddr* )&servaddr,in_len) < 0 ) 
        {   

                printf("not connect to internet!
 ");
                close(fd);
                return 0; //没有联网成功
        }   
        else
        {   
                printf("=====connect ok!=====
");
                close(fd);
                return 1;
        }   
}