Get time object from the web?

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

On 22.01.2010 07:44, Jose W. wrote:

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

Kinda, sorta: http://rubyforge.org/projects/net-ntp/

You’d’ve to parse what NET::NTP returns into a proper Time object, but
you get the time from an NTP server.

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

It depends on what the web clock is.
If you can get the time arguments from it (like day, month, year,hour,
minute, second etc), you could use Time.local to create a time object.

HTH.
Jeff.

Jose W. wrote:

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

Instead of using NTP you can simply download some page, via HTTP, from a
webserver whose clock you trust to be sufficiently accurate. Servers
send a Date header, which you can use.

Example from the shell:

wget -q -d -O /dev/null http://google.com 2>&1 | grep ^Date

Friday, January 22, 2010, 4:21:08 AM, you wrote:

SK> Jose W. wrote:

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

SK> another way:
SK> http://juretta.com/log/2006/08/26/ruby_contacting_a_timeserver/

SK> hth,

SK> Siep

In that URL cited, there is a comment that reads

you might want to cache the Cache result… it won’t change :wink:

What does this mean?

Ralph

On Fri, Jan 22, 2010 at 11:43 AM, Ralph S. [email protected]
wrote:

SK> another way:
SK> http://juretta.com/log/2006/08/26/ruby_contacting_a_timeserver/

In that URL cited, there is a comment that reads

you might want to cache the Cache result… it won’t change :wink:

What does this mean?

The code (full code is below for ease of reference) says that
the time server returns the number of seconds from 1900-01-01.
The Ruby Time class works with the number of seconds
from 1970-01-01, so to use the seconds to create a Time object
we need to adjust the seconds returned from the time server
by the number of seconds from 1900-01-01 to 1970-01-01.
That number of adjustment seconds won’t change,
so once it has been calculated using get_seconds_diff_1970_1900
that adjustment can be stored for future use.

So you could do something like:
adjustment_secs_1900_to_1970 = get_seconds_diff_1970_1900
and then
seconds = Net::Telnet.new(options).recv(4).unpack(‘N’).first
remote_time = Time.at( seconds - adjustment_secs_1900_to_1970 )

Does that explain what you were asking about?

code at

http://juretta.com/log/2006/08/26/ruby_contacting_a_timeserver/
require ‘net/telnet’
TIME_SERVER = ‘ntp2.fau.de

options = {
“Host” => TIME_SERVER,
“Telnetmode” => false,
“Timeout” => 30,
“Port” => “time”
}

The time is the number of seconds since 00:00 (midnight) 1 January

1900

GMT, such that the time 1 is 12:00:01 am on 1 January 1900 GMT; this

base will serve until the year 2036.

seconds = Net::Telnet.new(options).recv(4).unpack(‘N’).first

The Ruby Time class handles dates with an epoch

starting at midnight january 1 1970

We have to use the Date class to work with pre-epoch dates.

require ‘date’
def get_seconds_diff_1970_1900

you might want to cache the Cache result… it won’t change :wink:

(DateTime.new(1970, 1, 1) - DateTime.new(1900, 1, 1)).to_i * 24 * 60 *
60
end

Convert seconds to a Time object

remote_time = Time.at(seconds -
get_seconds_diff_1970_1900).strftime("%Y-%m-%d %H:%M:%S")

print “Time from #{TIME_SERVER} -> #{remote_time}”

Great! It seems to work, but, can someone help me for making a class
with that code, that will return that time object? Like this:

@now = ServerTime.get_time

@now is now the time object returned by that server…

I’m very new to Ruby, but I do know it is great :open_mouth:

Jose W. wrote:

Hello there.
I was wondering if, it was possible to connect to the internet and
create a time object (Time.new) from a web clock?

another way:
http://juretta.com/log/2006/08/26/ruby_contacting_a_timeserver/

hth,

Siep

On Sat, Jan 23, 2010 at 12:34 AM, Jose W. [email protected]
wrote:

Great! It seems to work, but, can someone help me for making a class
with that code, that will return that time object? Like this:
@now = ServerTime.get_time
@now is now the time object returned by that server…

The following seems to work, but it isn’t “production code”
because it doesn’t deal with timeouts or other failures,
which should perhaps return nil or raise an exception.

based on code at

http://juretta.com/log/2006/08/26/ruby_contacting_a_timeserver/
require “net/telnet”

class ServerTime
attr_reader :host
TIME_SERVER = ‘ntp2.fau.de

25567 = 70 * 365 + 70.div(4); this is not a general formula

for converting periods of years to seconds: leap years need

careful handling; also this ignores leap seconds.

SECONDS_1900_01_01_TO_1970_01_01 = 25567 * 24 * 60 * 60

def initialize( host_v = nil )
@host = host_v || TIME_SERVER
@options = {
“Host” => @host,
“Telnetmode” => false,
“Timeout” => 30,
“Port” => “time”
}
end

Note that this does not deal with what happens if there is a

timeout

or other failure to get the time from the time server.

def time()
# The time is the number of seconds since 00:00 (midnight) 1
January 1900
# GMT, such that the time 1 is 12:00:01 am on 1 January 1900 GMT;
this
# base will serve until the year 2036.
seconds = Net::Telnet.new(@options).recv(4).unpack(‘N’).first
Time.at( seconds - SECONDS_1900_01_01_TO_1970_01_01 )
end
end

st = ServerTime.new
t = st.time
puts “Time from #{st.host} -> #{t}”
sleep 3
puts “Time from #{st.host} -> #{st.time}”

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