you should actually only have to compute a millisecs offset once at net connection -- bit of a pain in the arse -- start off sending timestamp packets from server to client, and the client responding with its timestamp/... time the round trip, if you get 3 or 4 in a row that are very close together in elapsed transit time, average the differences between server and client timestamps, adjust for average lag, then send a packet to the slave telling it what offset to use.
This is the same basic idea used by unix the unix rtime command to remotely sync a computer clock.
This is the same basic idea used by unix the unix rtime command to remotely sync a computer clock.