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Ruby: Contacting a timeserver

August 26, 2006

The TIME protocol is an internet protocol defined in http://www.faqs.org/rfcs/rfc868.html

This script shows how to connect to an arbitrary TIME-Server using Ruby's Net::Telnet library.

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 ;-)
  (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}"

1. http://attachr.com/3911
2. TIME protocol
3. www.ntp.org
4. http://ntp.isc.org/bin/view/Servers/WebHome
5. Wikipedia: Network Time Protocol
6. Net::Telnet
7. RFC 958
8. Ruby Date

Kudos to Peter Cooper who pointed out that we are using the TIME protocol (TCP on port 37) not NTP on UDP port 123!