> On Feb 23, 2015, at 4:20 PM, Rick Mann <[email protected]> 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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