C # obtain the standard network time

Using Microsoft. VisualBasic;
Using system;
Using system. collections;
Using system. Collections. Generic;
Using system. Data;
Using system. diagnostics;
Using system. IO;
Using system. net;
Using system. net. Sockets;
Using system. runtime. interopservices;
Namespace spider
{
Public class daytime
{
// Internet time server class by Alastair Dallas 01/27/04

// Number of seconds
Private const int threshold_seconds = 15;
// That Windows clock can deviate from NIST and still be okay

// Server IP addresses from
// Http://www.boulder.nist.gov/timefreq/service/time-servers.html
Private Static string [] servers = {
"129.6.15.28 ",
"129.6.15.29 ",
"13.03.4.101 ",
"13.03.4.102 ",
"13.03.4.103 ",
"128.138.140.44 ",
"192.43.244.18 ",
"131.107.1.10 ",
"66.243.43.21 ",
"216.200.93.8 ",
"208.184.49.9 ",
"207.126.98.204 ",
"205.188.185.33"

};
Public static string lasthost = "";

Public static datetime lastsystime;
Public static datetime gettime ()
{
// returns UTC/GMT using an NIST server if possible,
// degrading to simply returning the system clock

// if we are successful in getting NIST time, then
// lasthost indicates which server was used and
// lastpolicime contains the system time of the call
// If lastpolicime is not within 15 seconds of NIST time,
// The system clock may need to be reset
// If lasthost is "", time is equal to system clock

String host = NULL;
Datetime result = default (datetime );

Lasthost = "";
Foreach (string host_loopvariable in servers)
{
Host = host_loopvariable;
Result = getnisttime (host );
If (result> datetime. minvalue)
{
Lasthost = host;
Break; // todo: might not be correct. Was: exit
}
}

If (string. isnullorempty (lasthost ))
{
// No server in list was successful so use system time
Result = datetime. utcnow;
}

Return result;
}

Public static int secondsdifference (datetime dt1, datetime dt2)
{
timespan span = dt1.subtract (dt2 );
return span. seconds + (span. minutes * 60) + (span. hours * 360);
}

Public static bool windowsclockincorrect ()
{
datetime NIST = gettime ();
If (math. ABS (secondsdifference (NIST, lastpolicime)> threshold_seconds)
{
return true;
}
return false;
}

Private Static datetime getnisttime (string host)
{
// Returns datetime. minvalue if host unreachable or does not produce time
Datetime result = default (datetime );
String timestr = NULL;

Try
{
Streamreader reader = new streamreader (New tcpclient (host, 13). getstream ());
Lastpolicime = datetime. utcnow;
Timestr = reader. readtoend ();
Reader. Close ();
}
Catch (socketexception ex)
{
// Couldn't connect to server, Transmission Error
Debug. writeline ("socket exception [" + host + "]");
Return datetime. minvalue;
}
Catch (exception ex)
{
// Some other error, such as stream under/Overflow
Return datetime. minvalue;
}

// Parse timestr
If (timestr. substring (38, 9 )! = "UTC (NIST )"))
{
// This signature shocould be there
Return datetime. minvalue;
}
If (timestr. substring (30, 1 )! = "0 "))
{
// Server reports Non-optimum status, time off by as much as 5 seconds
Return datetime. minvalue;
// Try a different server
}

int JD = int. parse (timestr. substring (1, 5);
int yr = int. parse (timestr. substring (7, 2);
int mo = int. parse (timestr. substring (10, 2);
int DY = int. parse (timestr. substring (13, 2);
int hR = int. parse (timestr. substring (16, 2);
int Mm = int. parse (timestr. substring (19, 2);
int SC = int. parse (timestr. substring (22, 2);

If (JD <15020 ))
{
// Date is before 1900
return datetime. minvalue;
}
If (JD> 51544 ))
yr + = 2000;
else
yr ++ = 1900;

Return new datetime (yr, Mo, Dy, HR, mm, SC );

}

[Structlayout (layoutkind. Sequential)]
Public struct systemtime
{
Public int16 wyear;
Public int16 wmonth;
Public int16 wdayofweek;
Public int16 wday;
Public int16 whour;
Public int16 wminute;
Public int16 wsecond;
Public int16 wmilliseconds;
}
[Dllimport ("kernel32.dll", charset = charset. ANSI, setlasterror = true, exactspelling = true)]
Private Static extern int32 getsystemtime (ref systemtime stru );
[Dllimport ("kernel32.dll", charset = charset. ANSI, setlasterror = true, exactspelling = true)]
Private Static extern int32 setsystemtime (ref systemtime stru );

Public static void setwindowsclock (datetime DT)
{
// Sets system time. Note: Use UTC time; windows will apply Time Zone

systemtime timestru = default (systemtime);
int32 result = default (int32);

timestru. wyear = (int16) dt. year;
timestru. wmonth = (int16) dt. month;
timestru. wday = (int16) dt. day;
timestru. wdayofweek = (int16) dt. dayofweek;
timestru. whour = (int16) dt. hour;
timestru. wminute = (int16) dt. minute;
timestru. wsecond = (int16) dt. second;
timestru. wmilliseconds = (int16) dt. millisecond;

Result = setsystemtime (ref timestru );

}
}
}