How to detect WIFI is down on 5600W

Hi,
Ive designed an application that uses WIFI at home for transmitting domotic datas to a web serveur. It works fine but my WIFI is weak sometimes and my module then disconnect from wifi. I know how to disconnect and reconnect by ifup and ifdown functions (it works fine) but I dont know how to detect that it is disconnected when it happends from an external reason. I thought that ifpending was the good function for that but when it disconnect (by a weak wifi link, when I force it by removing the antenna for instance) ifpending does not change its return value.

Is there some other function to use for detecting a disconnected WIFI link ?

Even if the WIFI power is OK, it will also happend for sure everytime the WIFI server renews the lease.

Thanks a lot for your help.