Compact Framework - System.Threading.Timer stops when the user turns off the screen

Question

I have an application that needs to "poll" a webservice to see if the user has any new messages waiting. I have no control over the webservice so I cannot switch to a "push" mechanism, I'm stuck making a request every X number of seconds to see what's available.

I am using a System.Threading.Timer to make the request every so often, but am encountering a few problems. The biggest is that it stops running when the phone is sent into "standby" mode (screen off, but still able to get calls and email/txt notifications).

I'd really like it to behave like other background applications. What can I do to make it work without being too big of a drain on the battery?

Answer 1

Hate to answer my own question, but I was pointed to this, which was able to perform even when the device is asleep. Looks like it's working perfectly.

Answer 2

There's nothing you can do, AFAIK. Standby mode is meant to suspend the processor to save power, and there's no way your code can execute if the processor isn't running. There are things your application can do to prevent the device from going into standby mode, but this really isn't advisable at all.

Answer 3

Yep. Similar to how MusiGenesis has answered, you won't be able to do much without keeping the device up and running. Similar to how some phones will notify that "Game/App Running" and thus your battery is being slapped around.

What about writing an interface from your phone to leverage text messaging (which still works) and get it to send a text message to the web service? Would that be possible? I'm guessing that sort of method might also stop running, but I figure it's a thought?

Answer 4

I'm not sure about compact framework, but in Win32 there is WaitableTimer that can wake up computer from standby. It takes some native calls though as there's no wrapper in .Net.

Answer 5

Although you can't modify the webservice, you might be able to add a second "shadow" webservice in between your clients and the original webservice. The shadow webservice could poll the original webservice and then "push" anything it finds out to the PDAs.

I think you might still have the same problem, though. I've never done "push" from a webservice, but I think it's basically implemented by having the client make an initial call to a webservice method that takes a delegate to a method in the client, which the webservice then hangs onto. When the webservice needs to push something, it calls that delegate. If the client has gone into standby mode in the meantime, the attempt to call the delegate from the server will fail.