[ENet-discuss] Time synchronization client/server/client communication.

[Alexander Shyrokov]

Hi Bill,

> client sends time-request packet to server
> server stamps and responds
> client takes the last send time, current time, figures out the *average*
> latency and adjusts the time to predict where the server is right now
> the client seems to always be a little bit off though and I think it's
> because the sending and receiving speed / packet delays are different.
> This would mean the client is /always/ over or under compensating.
Use your procedure to get initial time difference between server time 
and local time as well as half latency. The next time you get the 
response, try to predict what the server time should be using 
information from your previous response. Obviously it will be off, but 
the direction will tell you which way you should shift your prediction.

lt - local time; st - server time; lt1 - request time; lt2 - response 
received time.
1) hl = (lt2 - lt1)/2
    dif = st - (lt1 + hl)

2) predicted_st = lt1 + dif + hl
    hl = hl + (st - predicted_st)

... repeat

You have two variables dif and hl that you estimate from your times in 
my example I assume that dif was done properly the first time around, 
while in fact you need to keep track of how much your prediction is off 
and see if you need to redo the process.

I did not try this, just my 2c. Let us know how you decided to solve the 
problem.

Blue skies,
Alexander