How Can I Synchronize the Client Machines CPU
Clock?
Overview..
1
What
is the Computer CPU Clock?.
1
How
does a CPU clock work?.
1
Why
doesn’t it stay accurate?.
2
Why
should you periodically synchronize the CPU Clock?.
2
How
can I synchronize the CPU Clock in my application?.
2
What
is SNTP?.
2
What
is SNTP Wizard v2?.
2
Simple
Diagram of Network Architecture?.
2
Could
you show me some example code for SNTP Wizard?.
3
[Visual
Basic]
3
[VBScript]
3
[Visual
C++]
3
[Visual
FoxPro]
4
Who
makes SNTP Wizard?.
4
Where
can I find more information on this product?.
4
If
you have a client server application you may have noticed that the database
entries with timestamps taken from the local machines CPU clock are not always
very accurate. A process that occurs simultaneously on multiple machines can
all have very different time entries. This is due to many reasons; the main
being the user just doesn’t set the clock very precisely. There are other
reasons though and that is due to the flaws in the CPU clock. All clock have a
minimal amount of time differential in their clock updates. This slight
imperfection in the accuracy can cause loss of time in the milliseconds to
almost a minute a day. This article discusses all the aspects of why you need
to synchronize your CPU clock and how to go about doing it with precision and
accuracy, not to mention dependability and reliability.
The
computer CPU clock is the timing device that is built-in to the motherboard to
keep track of the current time and date. The clock is generally battery backed
up so that the time is kept current even when no power is applied to the
machine. Every computer on the market has a basic clock and many electronic
devices have them. The CPU clock is very important since it is used as the
basis for many operations undertaken by applications and hardware. One example
is communications. Serial communications as well as Parallel port
communications depend on the CPU clocks frequency counts to control the
transmission process of the data flow. A very large number of business
applications require the use of the CPU clock as well for logging functions,
data processing, database entries, charting functionality and more.
The
CPU clock works off of a quartz crystal. Quartz -- which is silicon dioxide
like most sand -- is unaffected by most solvents and remains crystalline to
hundreds of degrees Fahrenheit. The property that makes it useful is that when
compressed or bent, it generates a charge or voltage on its surface. This is
called the piezoelectric effect. In the same way, if a voltage is applied,
quartz will bend or change its shape very slightly.
A
quartz crystal is used within the clock. Often, these crystals are made from
thin sheets of quartz plated like an integrated circuit and etched chemically
to shape. The major difference between good and indifferent time keeping is the
initial frequency accuracy and the precision of the angle of cut of the quartz
sheet with respect to the crystalline axis. If contaminants are able to reach
the crystal, the accuracy can be affected.
The
electronics of the clock initially amplifies noise at the crystal frequency.
This builds or regenerates into oscillation -- it starts the crystal ringing.
The output of the crystal oscillator is then converted to pulses suitable for
the digital circuits. These divide the crystal's frequency down to translate
into time. Devices use the clocks pulses for driving processes that they need
very precise timing for.
No
watch or clock is perfect. The Atomic clocks are the closest to being perfectly
accurate as possible, but the standard quartz clock can have small deviations.
Many computers will lost from a few hundred milliseconds to up to a few second
every single day. Considering the average user sets the clock by the minute and
then factoring that they don’t reset the clock for months, it is quite possible
the time the computer’s CPU clock registers is actually very incorrect. The
time keeping flaw is very insignificant when looked at over a small period of
time but multiply the flaw by a large period of time and the issue becomes very
noticeable.
Due
to the inaccuracy of the time keeping mechanism it is important to reset the
clock to the exact time periodically. It may be overkill to set it more than
daily but setting it every morning is generally a pretty good idea. This keeps
the clock the most accurate during the workday. It is also possible that the
user may have mistakenly set the clock to the wrong time or date. It is quite
common that a user will set the clock by their watch or some other device that
is already registering a deviated time. It is general knowledge that the
average clock is set an accuracy of only minutes. Very rarely do people set
their watch or desk clocks to the second. If you then add the deviation from
the correct time plus the deviation they set their CPU clock from their watch
you will notice a large degree of inaccuracy.
A
program that is running on the machine can easily synchronize the CPU clock.
The best method of synchronization is to request the current time from a highly
accurate source. One such method is to interface with a radio frequency clock
or perhaps an atomic clock. This is possible using the SNTP or Simple Network
Time Protocol.
The
Simple Network Time Protocol is used for the synchronization of time and date
information from a time server. Some time servers are just a standard PC server
and returns the time from its local clock, other time servers are much more
accurate and they return the time from an Atomic Clock or a highly accurate
radio frequency clock. SNTP uses the UDP transmission method and sends a packet
request to the server. The server then responds with a specially formatted data
packet that contains the time information as well as some information that
allows for the calculation of the packet delay so that a more accurate reading
can be made. When a packet is sent over the Internet, the target recipient does
not instantly receive the data. There is a latency time for the send and
receive process and this needs to be calculated so that it can be applied to
the time returned by the server, otherwise the data would be incorrect. The
protocol also specifies that the returned time is sent in UTC or Universal
Coordinated Time (also known as Greenwich Mean Time).
SNTP
Wizard v2 is an ActiveX control (OCX) that implements the Simple Network Time
Protocol (SNTP) and allows for an easy to use interface for programmers. The
control provides a high level abstract view of how the protocol is implemented.
The use of the control allows for the simple setting of a time server and then
issuing the GetTime command which synchronizes with the server and grabs the
exact time from it. It has the option of also automatically setting the local
machine CPU clock to the retrieved time for the most accurate setting of the
clock. (No delays for the invoking code processing the returned data)
The
SNTP only returns the time data in Universal Coordinate Time, SNTP Wizard
automatically provides both the UTC time and a converted Local time which takes
into account the local machines Time Zone and converts it to the proper time.
This makes implementation even easier.
One
of the key features for this product is the ability to use it for Time
Stamping. You can guarantee that all DATE and TIME record entries are accurate
and in synch with the other applications. For distributed applications though
we recommend using the Universal Coordinated Time as the main data Time/Date
record entry and if possible using the Local time as a secondary entry. This
way your application can determine the Time Zone setting but all the
applications can see the actual time the data was created. Conflicts can occur
when different time zones otherwise.
The
code below is a basic example of using the Product. Please look for your
language to see the implementation.
Assumptions:
Form
created with 3 Textboxes, 1 checkbox,
and 1 SNTPWizard control.
Code:
Dim
lTimeDiff As Long
SNTPWizard1.TimeServer
= txtTimeServer.Text
SNTPWizard1.TimeServerPort
= CInt(txtTimeServerPort.Text)
SNTPWizard1.TimeOut
= CInt(txtTimeOut.Text)
SNTPWizard1.AutoSetLocalClock
= IIf(chkSetLocaltime.Value, True, False)
lTimeDiff
= GetTickCount()
If
SNTPWizard1.GetTime Then
lTimeDiff = GetTickCount - lTimeDiff
If (chkUseEvents.Value = 0) Then
lblLocalTime = "Local time:
" & CStr(SNTPWizard1.LocalTime)
lblUTCTime = "UTC
: " &
CStr(SNTPWizard1.UTCTime)
End If
Else
If (chkUseEvents.Value = 0) Then
lblLocalTime = "Error#" & SNTPWizard1.LastErrorNumber
lblUTCTime = SNTPWizard1.LastErrorDescription
End If
End
If
MsgBox
"Seekford Solutions, Inc. SNTP Wizard VBScript Example"
dim
MySNTPWizard
set
MySNTPWizard =
CreateObject("SNTPWIZARD.SntpWizardCtrl2")
MySNTPWizard.UnlockSNTPWizard("")
'<------- ENTER SERIAL NUMBER HERE
MySNTPWizard.TimeServer
= "time.mit.edu"
if
(MySNTPWizard.GetTime()) then
msgbox("UTC
Time: " +
cstr(MySNTPWizard.UTCTime) + vbcrlf + "Local Time: " +
cstr(MySNTPWizard.LocalTime))
else
msgbox("Error!" + vbcrlf + "Error Number:" + CStr(MySNTPWizard.LastErrorNumber)
+ vbcrlf + "Error Description:" + MySNTPWizard.LastErrorDescription)
end
if
MsgBox
"Please Visit http://www.SeekfordSolutions.com and purchase a license for this
great product!"
Assumptions:
Dialog
with 1 SNTPWizard, 3 Textboxes, 1 Checkbox
Member
variables –
m_SNTPWizarad
associated with SNTPWizard control
m_iTimeOut,
m_sServer, and m_iPort associated with textboxes
m_bAutoSet
associated with the checkbox
Code:
CString
sTemp;
m_SNTPWizard.UnlockSNTPWizard("");
UpdateData(TRUE);
m_SNTPWizard.SetTimeOut(m_iTimeOut);
m_SNTPWizard.SetTimeServer(m_sServer);
m_SNTPWizard.SetTimeServerPort(m_iPort);
m_SNTPWizard.SetAutoSetLocalClock(m_bAutoSet);
if (m_SNTPWizard.GetTime())
{
sTemp.Format(“%s\r\n%s”, CString("Local Time: ") +
COleDateTime(m_SNTPWizard.GetLocalTime()).Format(),
CString("UTC
Time: ") +
COleDateTime(m_SNTPWizard.GetUTCTime()).Format());
AfxMessageBox(sTemp);
}else
{
sTemp.Format(“%s\r\nError#: %d”, m_SNTPWizard.GetLastErrorDescription(),
m_SNTPWizard.GetLastErrorNumber());
}
&&
This code will retrieve the current time from the internet
MessageBox( "Seekford Solutions, Inc.
SNTP Wizard Foxpro Example")
local MySNTPWizard
MySNTPWizard =
CreateObject("SNTPWIZARD.SntpWizardCtrl2")
MySNTPWizard.UnlockSNTPWizard("") &&<-------
ENTER SERIAL NUMBER HERE
MySNTPWizard.AutoSetLocalClock = .t. &&
This tells SNTP Wizard to automatically set the client CPU Clock
MySNTPWizard.TimeServer = "time.mit.edu"
if (MySNTPWizard.GetTime())
then
messagebox("UTC Time:
" + TTOC(MySNTPWizard.UTCTime) +
chr(13) + "Local Time: " + TTOC(MySNTPWizard.LocalTime))
else
messagebox("Error!" +
chr(13) + "Error Number:" + Str(MySNTPWizard.LastErrorNumber)
+ chr(13) + "Error Description:" +
MySNTPWizard.LastErrorDescription)
endif
messageBox( "Please Visit
http://www.SeekfordSolutions.com and purchase a license for this great
product!")
Seekford
Solutions, Inc. is a software development corporation specializing in the
design and development of state of the art ActiveX controls and custom
projects. Their core product line is focused on Internet technologies primarily
in the facilitation of the use of the common Internet protocols. The design
philosophy is based on ease of use and quick implementation time. They also
handle custom projects for clients who are need of specialty software or who
need a framework base to use. The company was founded in early 2001. Their
website is
http://www.seekfordsolutions.com/.
It
is available from Seekford Solutions, Inc. at the products website of
http://www.seekfordsolutions.com/Products/SNTPWizard
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