How to accurately sync time between iPhones?

Question

I am writing an application that will require me to sync the time on a large number of iPhones accurately (to within a fraction of a second). As far as I can tell, access to the time function of the GPS is not available. If I sync over the Internet, then the biggest problem is network latency. The delay before the answer to a request is received can be estimated to be half the round trip - but how accurate can I expect this to be? Would it be worthwhile sending multiple requests and averaging or is there another better way of synchronising time?

score 4 · Accepted Answer · answered Feb 15 '10 at 05:49

4

Try implementing Marzullo's algorithm, as notably used in NTP.

answered Feb 15 '10 at 05:49

David

2,947
1
25
19

See http://stackoverflow.com/questions/2269532/network-time-protocol-for-iphone for information on implementing NTP on the iPhone – Casebash Feb 17 '10 at 22:07
@David, Is this how Emerald Time does it? – Pacerier Jan 10 '18 at 00:17

How to accurately sync time between iPhones?

1 Answers1

Linked