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Asked: 2026-05-24T23:47:21+00:00

I have a client that every 8 seconds will send a packet to a

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I have a client that every 8 seconds will send a packet to a server. If the server detects the packets are sent too fast it will disconnect the client. In the client I call Sleep(8000); before sending the packet. On the server side I use GetTickCount(); to calculate the time between the packets. I expected this to work without any problems but I keep getting disconnected.

I used WireShark to check the packet times and this is what I got:
Packet# Time
17 8.656064
72 16.957240
115 24.764741

24.764741 – 16.957240 = 7.807501 < 8 is the reason why I got disconnected.
I don’t understand this because in the client I call Sleep(8000); so it should send packets every 8 seconds or more.

The 2nd packet is late 0.3 second and the 3rd one is early about 0.2.
Is there a way to send these packets in time?

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1 Answer

  1. Editorial Team

    The problem is actually an age old one; TickCount varies, even between multiple CPUs in the same computer:

    http://social.msdn.microsoft.com/Forums/en-US/netfxbcl/thread/22c68353-1dbb-4718-a8d2-0679fdc0c298/

    My suggestion is set your Sleep to higher then 8000, say 9500, and keep the same mechanic for tickCount, therefore Sleep should always be higher.

    Another link to read is here:

    http://en.wikipedia.org/wiki/Latency_(engineering)#Computer_hardware_and_operating_system_latency

    With specific reference to the paragraph on Microsoft Windows.

    Update:

    I’m not sure why this is getting downvoted but allow me to clarify the problem, as I see it, here.

    TickCount cannot be relied upon as a specific measure of time, other then when it’s localised to one processing unit.
    The first link to MSDN provides citation as to why.

    Secondly, Windows itself may have inaccuracies in its timer logic.

    Lastly, in and of itself, your Crystal based timers may differ as it’s known that atmospheric conditions affect piezoelectric oscillation.

    http://en.wikipedia.org/wiki/Crystal_oscillator#Temperature_effects

    In summary, TickCount isn’t reliable and Getting absolute precision in sending packets over a network is a hard thing to achieve over consumer grade networks.

    My solution, to ensure that the Sleep timer waits longer then the Tick timer isn’t elegant, but enough of a ‘fudge’ to solve the problem.

    You can’t guarantee that a packet will arrive within X seconds, but you can make pretty sure that it won’t be sent before a certain duration has passed.

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