Question Network Time

I'd like to have access to a timestamp that is the same on the server and client. The manual on time synchronization suggests the NetworkTimeSystem should be able to provide me with one. The documentation is lacking but from the names I would think TimestampMS would be the field I want. Except it isn't: it returns different times on different instances.

I'd like such a timestamp because I have items moving on rails. If I spawn such an item I'd only have to synchronize its starting point and starting time, and I'd be able to predict and interpolate it without further data until it detaches or reaches the end of the rail.

Does such a timestamp currently exist? Or should I be looking for ticks instead of times? If so, are there different ticks (server/prediction/interpolation) and how would I access them?

 

Something that I've used in a similar situation is the server tick. I've got this value like this.

Code (CSharp):

1.         uint tick = 0;
2.         if( isClient )
3.             tick = clientSimulationSystemGroup.ServerTick;
4.         else
5.             tick = serverSimulationSystemGroup.ServerTick;

 

Well, I was using ServerSimulationSystemGroup.ServerTick and ClientSimulationSystemGroup.ServerTick and for a while it looked good. But on closer inspection they seem to start out at the same value and then they diverge. I didn't notice it at first because I was running only short tests.

In my case the client's tick count goes up faster than the server. I don't think it has to do with prediction because as I said, the ticks start out the same. The client won't just go ahead a few ticks, they actually keep adding up until the client is 100s of ticks ahead. Mind you this is still ClientSimulationSystemGroup.ServerTick I'm talking about getting ahead of ServerSimulationSystemGroup.ServerTick. For good measure I tried switching to ClientSimulationSystemGroup.InterpolationTick but it does the same thing. InterpolationTick is a handful of ticks behind ServerTick, but they both end up being far greater than ServerSimulationSystemGroup.ServerTick is.

Is there anything I need to do to get the actual tick number the server is on? I don't mind lagging behind, I'll settle for an interpolation tick. Do I need to set and/or retrieve it from a system in a certain group?

 

Thanks for the explanation! However, this would only explain differences up to about 32 ticks. As I described my tick difference gets much higher. The longer I let it run the higher the difference gets, eventually resulting in differences of 100s or even 1000s of ticks. It's pretty reliably 10% ahead, so if my server says it's at tick 9800 then my client will think the server is at tick 10780. And this is running on either on the same machine (host and client) or on a LAN where there really isn't a large or unreliable RTT.

Since the server obviously is in charge of the simulation I'm guessing the client's estimate of the server tick is just plain wrong here. Is there any test I can run or entity to inspect to find out what's happening here?