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Time Syncing Through a Firewall Without NTP?

Posted by Cliff on from the route-around-the-problem dept.

dvdsmith asks: "Say are dealing with a Windows network that for internet access must pass through a firewall that you have no control over. Said firewall apparently blocks the known time protocols (NTP,daytime,etc) and you know from experience that those who control it will not allow any exceptions. If one sets up an internal NTP server (Windows XP or 2000 workstation) for all others to sync from, is there another reliable method for updating time on the server, like pulling from a Java website? See the time.gov website as an example. Any ideas?"

6 of 112 comments (clear)

  1. radio by F�an�ro · · Score: 4, Interesting

    you could build a device that gets the time via radio (LINK) or buy one that does this (like a gps receiver?).

    or if any udp port is open in the firewall, set up a ntp server outside that answers on that port

  2. Re:too easy by Anonymous Coward · · Score: 2, Interesting
    Just write a batch file or shell script to get the time from any website that shows the current time of refresh on a page.

    How about
    $ wget --spider -S $WEBSITE 2>&1 | grep -i 'date:'
    No need to parse the HTML, just use standard HTTP headers.
  3. Synced with what? by spaceyhackerlady · · Score: 3, Interesting

    Do the systems need to be synced to the outside world, or merely consistent with each other?

    If the silly firewall people won't help you (you might remind them that you do in fact work for the same company...), you need to set up your own NTP server. Either a real one with a GPS receiver, or a pretend one that everybody can follow and have the same time, regardless of what that time actually is (see initial question).

    The occasional phone call to the NIST's dialup time server might be useful too.

    ...laura

  4. Ask for an NTP source by ken95357 · · Score: 2, Interesting

    Why not ask the firewall people if they have an NTP source you can use? If they don't, ask them to set one up for you that way they don't have to open their firewalls to your NTP needs.

  5. TV tuner card by Hangeron · · Score: 2, Interesting

    I have a cheap Hauppauge WinTV card and I sometimes use alevt-date in linux to set clock. I've setup a script that sets clocks on 3 other computers aswell through ssh.

  6. Hardware boxes by wcdw · · Score: 2, Interesting

    This is not what the submitter wanted to know. However, for all of you who have proposed hardware GPS-based solutions, you might want to note that there are also companies making similar hardware which get their time signal from the CDMA cellphone signals.

    CDMA in turn gets its time from GPS, but is far easier to receive in most locations - no need to run an antenna cable up to the roof. They also tend to be cheaper.

    --
    If you're not living on the edge, you're just taking up space!