C/C++ :: How To Calculate NTP Timestamp To Unix Epoch Time
Mar 18, 2015
I have been trying for several months to create a simple SNTP single Client/Server based on RFC5905. Finally I manage to make it work at least I think it works correctly, but when I tried to test my code against a real NTP server (e.g. 0.se.pool.ntp.org:123) the timestamps that I am receiving need to be recalculated. I have tried several different approaches but no matter for 3 days now but no matter what I tried nothing yet.
The problem that I am having in not so much programming error is more about knowing how the NTP server operates.
How to convert the NTP timestamp to Unix epoch timestamp?
Syntax to execute the Server e.g. ./server 127.0.0.1:5000 and Client e.g. ./client 127.0.0.1:5000
Syntax to execute the Client against a real NTP server e.g. ./client 0.se.pool.ntp.org:123
Sample of working code Client:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
[code]....
Sample of printed output when I use Server and Client.
Reference Identifier 0 LOCL
Reference Timestamp 0.0 1426637081.3564398733
Originate Timestamp 1426637087.3570333925 1426637087.3570333925
Receive Timestamp 1426637087.3570334078 1426637087.3570334003
Transmit Timestamp 1426637087.3570333925 1426637087.3570334046
Sample of printed output when I am probing a real NTP server (e.g. 0.se.pool.ntp.org:123).
Reference Identifier 0 $
Reference Timestamp 0.0 3879449560.3503094062
Originate Timestamp 1426637090.3573978972 1426637090.3573978972
Receive Timestamp 1426637090.3573992772 2722083800.781009125
Transmit Timestamp 1426637090.3573978972 2722083800.937312997
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Sep 1, 2014
I am converting unix timestamp to datetime format like this:
static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
static readonly double MaxUnixSeconds = (DateTime.MaxValue - UnixEpoch).TotalSeconds;
public static DateTime UnixTimeStampToDateTime(double unixTimeStamp) {
return unixTimeStamp > MaxUnixSeconds
? UnixEpoch.AddMilliseconds(unixTimeStamp)
: UnixEpoch.AddSeconds(unixTimeStamp);
}
use it:
Console.WriteLine("From UNIX do datetime 1300123800440 : " + UnixTimeStampToDateTime(1300123800440));
output: 14.03.2011 5:30 PM
Now i would like to have function which convert it back to unix timestamp but unfortuently my new function is cutting down last 3 digits for instance:
public static long UnixTimestampFromDateTime(DateTime date) {
long unixTimestamp = date.Ticks - new DateTime(1970, 1, 1).Ticks;
unixTimestamp /= TimeSpan.TicksPerSecond;
return unixTimestamp;
}
after use of it i am retrieving:
Console.WriteLine(UnixTimestampFromDateTime(Convert.ToDateTime("14.03.2011 5:30 PM")));
result:
1300123800
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HTML Code:
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Here's the actual timestamp block of code:
HTML Code:
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[Code] ....
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