嵌入式linux c/c++检测联网思路及代码

最近做嵌入式linux有检测联网状态的需求，百度了一下其他方案，采用ping dns方案比较稳定合适，ping多个dns服务器，以及自己的后台服务器，任意一个能ping通，则说明设备已联网。

QMutex paltform_main_mutex;
int _net_connected = 0;
int _check_networking_complete = 1;

/**
 * @brief Set the net connected object
 *
 * @param connected
 */
void set_net_connected(int connected)
{
  QMutexLocker locker(&paltform_main_mutex);
  _net_connected = connected;
}

/**
 * @brief net connected
 *
 * @return int
 */
int net_connected()
{
  QMutexLocker locker(&paltform_main_mutex);
  return _net_connected;
}

/**
 * @brief Set the net connected object
 *
 * @param connected
 */
void set_net_connected(int connected)
{
  QMutexLocker locker(&paltform_main_mutex);
  _net_connected = connected;
}

/**
 * @brief check networking complete
 *
 * @return int
 */
int check_networking_complete()
{
  QMutexLocker locker(&paltform_main_mutex);
  return _check_networking_complete;
}

/**
 * @brief check_networking_thread
 *
 * @param arg
 * @return void*
 */
static void *check_networking_thread(void *arg)
{
  FILE *fp;
  char buffer[80];

  memset(buffer, 0, sizeof(buffer));
  fp = popen("ping 8.8.8.8 -c 3 |grep 'ttl='", "r");
  fgets(buffer, sizeof(buffer), fp);
  pclose(fp);
  if (strlen(buffer) > 0)
  {
    ALOGD("[%s]: google dns ok, device is networking", __func__);
    set_net_connected(1);
    set_check_networking_complete(1);
    return NULL;
  }

  memset(buffer, 0, sizeof(buffer));
  fp = popen("ping 114.114.114.114 -c 3 |grep 'ttl='", "r");
  fgets(buffer, sizeof(buffer), fp);
  pclose(fp);
  if (strlen(buffer) > 0)
  {
    ALOGD("[%s]: china dns ok, device is networking", __func__);
    set_net_connected(1);
    set_check_networking_complete(1);
    return NULL;
  }
 set_net_connected(0);
  ALOGD("[%s]: device is not network", __func__);
  set_check_networking_complete(1);
  return NULL;
}

/**
 * @brief check networking
 *
 */
void check_networking()
{
  if (!check_networking_complete())
  {
    return;
  }
  set_check_networking_complete(0);
  pthread_t _thrd;
  if (pthread_create(&_thrd, NULL, check_networking_thread, NULL))
  {
    ALOGE("create check_networking_thread failed, "
          "errno: %d (%s)",
          errno, strerror(errno));
    set_check_networking_complete(1);
    return;
  }
  pthread_detach(_thrd);
}

定时执行check_networking()方法进程，使用net_connected()判断是否联网。