Re: Monitoring host reachability and the SCNetwork API
Re: Monitoring host reachability and the SCNetwork API
- Subject: Re: Monitoring host reachability and the SCNetwork API
- From: Allan Nathanson <email@hidden>
- Date: Thu, 16 Apr 2009 14:20:59 -0400
Can you provide a bit more "code"?
... and what version of the OS are you testing on / targetting?
Also, what do you get from "scutil -d -v -r google.com"?
- Allan
On Apr 16, 2009, at 2:02 PM, Jeremy W. Sherman wrote:
Hello all,
I wish to monitor reachability of a host and receive a callback if its
reachability changes. It seemed the System Configuration framework
provided just what I needed. But a simple test appears to indicate
that the framework is unreliable for my purposes.
I am connected to the Internet. But checking reachability of
google.com via SCNetworkCheckReachabilityByName("google.com", &flags)
yields flags of 0x0002, kSCNetworkConnectionRequired. The results of
using an SCNetworkReachability installed on the runloop agree: a
connection is required, and cannot be automatically established.
The documentation for the ConnectionRequired flag states: "This flag
indicates that the specified nodename or address can be reached using
the current network configuration, but a connection must first be
established. As an example, this status would be returned for a dialup
connection that was not currently active, but could handle network
traffic for the target system." Even if a connection did have to be
established, I would expect kSCNetworkConnectionAutomatic to be set.
I was interpreting the returned reachability flags as "the host can be
reached if it is ((Reachable or ConnectionAutomatic) and not
InterventionRequired)"; this does not seem to work, because
SystemConfiguration appears unaware of my actual connection status and
current network reachability.
Is there a better, working way to monitor the reachability of a host?
I can use anything daemon-safe (so pretty much Foundation.framework on
down).
Also, did I misunderstand something about SystemConfiguration's
reachability API, or is it just unhelpful/stuck in a dial-up age?
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