NtpResponse Exception

Question

Hello, I am new about your library, and for my test when I try to retrieve the TimeSpan from NtpResponse I had an "System.OverflowException" with this stack trace:

at Rebex.Net.NtpTimestampDifference.Add(NtpTimestampDifference value) at Rebex.Net.NtpTimestampDifference.op_Addition(NtpTimestampDifference a, NtpTimestampDifference b) at Rebex.Net.NtpResponse.get_TimeOffset()

This is my sample code: ` {

string serverName = Console.ReadLine();

Ntp ntp = new Ntp(serverName)
    {
        VersionNumber = NTP_PROTOCOL_VERSION,
        Timeout = NTP_REQUEST_TIMEOUT_MS
    };

NtpResponse response = ntp.GetTime();

TimeSpan ntpServerDelta = response.TimeOffset.ToTimeSpan();
DateTime currentTime = DateTime.UtcNow + ntpServerDelta;

Console.WriteLine("The server current time is {0} ", currentTime);

Console.ReadLine();

}`

This occurred when I have a big difference between the server and my local machine.

How can I solve this?

Thanks in advance.

Comments

Any idea???

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Hello, sorry for the delay! We are currently looking into this issue. What was the time on your local machine and server, by the way?

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Hello, no problem! My local machine has the current date time (8 October 2013) but the server has very old time something like 10 January 1973. Thanks

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Thanks! It looks like time differences larger than about 34 years (actually new TimeSpan((1L + uint.MaxValue) / 4 * 10000000L) are causing an OverflowException due to a limitation in NtpTimestampDifference structure's minimum/maximum values (+- 78 years).

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Additionally, the NtpTimestamp object limited currently only supports values in 1900 to 2036 range, which means years >2036 also cause issues.

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We will definitely fix both of these issues for the next release and mail you a link to a hotfix when it's ready. Thanks for reporting this, and sorry for inconvenience!

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OK Thanks. In the meanwhile can I use this work around ??:

private static DateTime CalculateCurrentTime(NtpResponse response)
{
    NtpPacket ntpPacket = response.Packet;

    NtpTimestamp serverTimeStamp = ntpPacket.TransmitTimestamp;
    NtpTimestamp localTimeStamp = ntpPacket.DestinationTimestamp;

    NtpTimestampDifference offset = serverTimeStamp - localTimeStamp;

    TimeSpan timeSpan = offset.ToTimeSpan();

    DateTime currentTime = DateTime.UtcNow + timeSpan;
    return currentTime;
}

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Yes, this should work. However, I just sent you a link to a hotfix that shoudl solve this issue. Please give it a try and let me know whether t works!

Answer 1

This error occured when the time difference between the local and remote time was larger than about 34 years. It has been fixed in Rebex Time 2013 R3.