title: I need to use NTP to serve a time offset from system time. Is broadcast the way to go?
body: <p>I have a closed network with a few nodes that are mutually consistent in time. For this I use NTP with one node as the NTP server. One of the nodes is a dumb box over which I have little control. It runs an sntp client to synchronize time to the system NTP server. I now need the box to be set to a time that is offset from the system time by an amount that I control. I am trying to find out if this can be done using only the available sntp client on the box. I will now present you my approach and would love to hear from anyone who knows if this can be done.</p>
  
  <p>As far as I found out a standard NTP server cannot be made to serve a time that is offset from the server's system time. I will therefore have to write my own implementation. The conceptually simplest NTP server must be a broadcast-only server. My thought is that I will be able to set the sntp box to listen to broadcast and then just send NTP broadcast packets set to my custom time.</p>
  
  <p>Are there any NTP server implementations that allow me to do this out of the box?</p>
  
  <p>Can anyone tell me how hard it is to write an sNTP broadcast server - or any other NTP server?</p>
  
  <p>Does anyone know of any tutorials for how to write an NTP server?</p>
  
  <p>Are there any show-stoppers to the scheme I am describing above?</p>
  
  <p>To try to answer the questions that will inevitably come up:</p>
  
  <ul>
  <li>Yes, I am also thinking about a new interface on the box to set the time to a value I specify. But that is not what I am asking about, and no, it will not be much simpler.</li>
  <li>I have inverstigated if I could just use the time that the box needs as the system time. This is not an option. I will need two different times, one for the system and one for the box.</li>
  </ul>
  
  <p>All insight will be appreciated! Even opinions like "it should be doable."</p>