[maemo-developers] How to detect that connectivity is lost

[From: Kalle Valo]

"ext Frantisek Dufka" <dufkaf at seznam.cz> writes:

> What I suggested was a workaround not solution, that's true. By
> pinging in regular intervals I mean using ping to send let's say 5 or
> 10 packets (ping -c 10) and then sleep e.g. 15 seconds. I did not mean
> pinging default gateway continuously.

For example in that case the standy time while associated to a WLAN
network would drop approximately 40%. I highly recommend not to use
this kind of method. 

But even if you do use this kind of method, please inform the users of
the application that the power consumption is higher than normally.
Users have right to know that installing the application affects the
usage times.

> I'm not sure you can solve this on lower levels completely without
> doing the same i.e. sending data to check they got through and back.

Sure we can, that's why WLAN has ACK frames. And we can use also Null
frames to check if the AP can still hear us.

> If you don't do this it will be too late for some situations. When you
> actually send data that matter and find the connection is dead, you
> need to reconnect and retry, which is not ideal.
>
> So it is compromise between battery power and comfort (i.e. high
> chance of having connection ready when you really need it).

Yes, it's a compromise. But this has to be a bug somewhere in our WLAN
stack. I will look into this and try to fix it.

-- 
Kalle Valo