I have create a little engineering app for some network debugging. It takes a list of IP addresses and pings them, with user set timeout and rate. It logs the average round-trip time and every time one of the sends fails it logs it's duration of failure and a timestamp of when it happened...
That's the idea. I developed it on a Win7 machine with .Net4 and have had to put the thing on a set of XP laptops.
The problem is the duration values on my box during testing show nice ms durations, on the XP boxes when I look they show 0 or 15.625 (magic number?)... and have the funny square, box symbol in the string?
public void LinkUp()
{
if (_isLinkUp) return;
_upTime = DateTime.Now;
var span = _upTime.Subtract(_downTime);
_downTimeLog.Add(new LinkDown()
{
_span = span,
_status = _ipStatus,
_time = _downTime
});
_isLinkUp = true;
}
That's the bit that does the log. The _ipStatus is the ping failure reason (typically timeout).
_downEventLog.AppendLine(" Duration-> " + linkDownLogEvent._span.TotalMilliseconds + "ms\n");
That's the bit that does the print... Can anyone shed any light on this apparent difference?
The question has been answered but I will include an edit here for some more info.
EDIT:
It seems that the difference was down not to the Win7 and WinXP difference but 32bit and 64bit.
In a 32 bit windows systems as Henk points out, the granularity of the system clock is 15-16ms, this is what gave me the value of 15.625 for every value less than 16ms for the timespan.
In a 64 bit system the system call is to a different set of methods that have a much finer granularity. So on my dev machine in x64 I had ms accuracy from my system clock!
Now, the stopwatch uses a hardware interface via the processor instrumentation to record a much finer granularity (probably not every processor tick, but I imagine something obscenely accurate in-line with this thinking). If the hardware underlying the OS does not have this level of instrumentation, it will however use the system time. So beware! But I would guess most modern desktops/laptops have this instrumentation... Embedded devices or things of that nature might not, but then the stopwatch class is not in the Compact Framework as far as I can see (here you have to use QueryPerformanceCounter()).
Hope all this helps. It's helped me a lot.
Somewhere around the _spanStopWatch initialiser:
if (!_spanStopWatch.IsHighResolution)
{
throw new ThisMachineIsNotAccurateEnoughForMyLikingException("Find a better machine.");
}
The nuts and bolts:
public void LinkUp()
{
if (_isLinkUp) return;
_spanStopWatch.Stop();
var span = _spanStopWatch.Elapsed;
_downTimeLog.Add(new LinkDown()
{
_span = span,
_status = _ipStatus,
_time = _downTime
});
_isLinkUp = true;
}