The SNTP module implements a Simple Network Time Procotol client. This includes support for the "anycast" NTP mode where, if supported by the NTP server(s) in your network, it is not necessary to even know the IP address of the NTP server.
When compiled together with the rtctime module it also offers seamless integration with it, potentially reducing the process of obtaining NTP synchronization to a simple
sntp.sync() call without any arguments.
Attempts to obtain time synchronization.
sntp.sync([server_ip], [callback], [errcallback])
nil, that server is used. If
nil, then the last contacted server is used. This ties in with the NTP anycast mode, where the first responding server is remembered for future synchronization requests. The easiest way to use anycast is to always pass nil for the server argument.
callbackIif provided it will be invoked on a successful synchronization, with three parameters: seconds, microseconds, and server. Note that when the rtctime module is available, there is no need to explicitly call
rtctime.set()- this module takes care of doing so internally automatically, for best accuracy.
errcallbackfailure callback with no parameters. The module automatically performs a number of retries before giving up and reporting the error.
-- Best effort, use the last known NTP server (or the NTP "anycast" address 188.8.131.52 initially) sntp.sync()
-- Sync time with 192.168.0.1 and print the result, or that it failed sntp.sync('192.168.0.1', function(sec,usec,server) print('sync', sec, usec, server) end, function() print('failed!') end )