Re: Reachability determination?
Re: Reachability determination?
- Subject: Re: Reachability determination?
- From: Jens Alfke <email@hidden>
- Date: Mon, 23 Feb 2015 17:12:22 -0800
On Feb 23, 2015, at 4:20 PM, Rick Mann < email@hidden> wrote:
I thought I've read in the past that we shouldn't use SCNetworkReachability to determine reachability, but to actually just try to connect to our servers, and if that fails, then do something.
What is that something? Looking at the SCNetworkReachability Reference, there's no mention of this usage.
We’ve been struggling with this too. As far as I know, the basic logic is that if the failure "looks like" it could be caused by an unreachable host, set a timer and retry periodically (probably with an exponential backoff.) Meanwhile, run a reachability observer, and if it’s told that the host became reachable, abort the timer and retry right now.
The “looks like” test seems to be a heuristic where you check various error codes in various NSError domains. The ones we look for currently are NSURLErrorDNSLookupFailed, NSURLErrorNotConnectedToInternet, NSURLErrorInternationalRoamingOff; but my colleague who’s working on this problem has probably added a few more that I haven’t seen yet…
—Jens |
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