iPhone app gets into a state where network request

问题:

Every so often, my iPhone app gets into a state where network requests always time out, even if other apps work fine (and can even access the same sites). This isn't obviously correlated with changes in network availability, and happens both on 3G and over WiFi. Any suggestions on how to diagnose the problem?

(FWIW, the app uses MonoTouch and HttpWebRequest, but I suspect whatever's going wrong is lower-level.)

Note: The problem persists through backgrounding the app and changing the network configuration; the only fix seems to be to kill the app and re-launch it.

Updates: I've tried making use of Reachability, but to no effect. Reachability.InternetConnectionStatus always returns ReachableViaWiFiNetwork (or ReachableViaCarrierDataNetwork, depending; likewise IsHostReachable() always returns true. Runtime.StartWWAN() seems to make no difference.

回答1:

There was a bug open about this at https://bugzilla.novell.com/show_bug.cgi?id=555439 and there were several attempts at resolving it. As of the last comment in the bug, it was presumed fixed but I guess if you are using MonoTouch 4.0.3 then there some cases that are not worked around.

Basically, the problem is reflected in this other Stackoverflow question: iPhone 3G Connection Enabling

What MonoTouch does to try and work around this issue is to call MonoTouch.Runtime.StartWWAN(Uri) which opens a dummy connection to the uri using an NSUrlConnection to force-wake the network interface. Then, MonoTouch goes back to using the BSD socket API inside the HttpWebRequest.

回答2:

Try setting the timeOutInterval property of the NSURLRequest used to make the call.