[time-nuts] Time syncing question

[Joseph Gray]

I have a piece of equipment that has its time set either via a serial port 
or via HTTP. After initial setting, the device keeps its own time (although 
badly). The device has no NTP capability itself. Although I'm describing a 
particular piece of equipment, I have seen many other devices that work the 
same way.

I want to write a program that runs on a standard PC and communicates the 
time to the device in question. The communication between the PC and the 
target device won't be a problem. The PC would be syncing it's time via NTP. 
The target device wouldn't need it's clock synced better than 100-200 mS or 
so.

I'd like to know how to handle syncing the target device's time. I know that 
I want to avoid major time jumps and that once the target device is synced, 
I need to keep things in sync. I know that NTPD knows how to do these 
things, but I don't want to delve into the source code of that quite yet. At 
this point, I'm looking for more of a high-level pseudo-code description of 
how this is handled. Any pointers to documentation of this type would be 
appreciated.