ntp

return({
    hour=0,
    minute=0,
    second=0,
    lastsync=0,
    ustamp=0,
    tz=1,
    udptimer=2,
    udptimeout=1000,
    ntpserver="194.109.22.18",
    sk=nil,
    sync=function(self,callback)
        local request=string.char( 227, 0, 6, 236, 0,0,0,0,0,0,0,0, 49, 78, 49, 52,
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
        )
        self.sk=net.createConnection(net.UDP, 0)
        self.sk:on("receive",function(sck,payload)
            sck:close()
            self.lastsync=self:calc_stamp(payload:sub(41,44))
            self:set_time()
            if callback and type(callback) == "function" then
                callback(self)
            end
            collectgarbage() collectgarbage()
        end)
        self.sk:connect(123,self.ntpserver)
        tmr.alarm(self.udptimer,self.udptimeout,0,function() self.sk:close() end)
        self.sk:send(request)
    end,
    calc_stamp=function(self,bytes)
        local highw,loww,ntpstamp
        highw = bytes:byte(1) * 256 + bytes:byte(2)
        loww = bytes:byte(3) * 256 + bytes:byte(4)
        ntpstamp=( highw * 65536 + loww ) + ( self.tz * 3600)   -- NTP-stamp, seconds since 1.1.1900
        self.ustamp=ntpstamp - 1104494400 - 1104494400      -- UNIX-timestamp, seconds since 1.1.1970
        return(self.ustamp)
    end,
    set_time=function(self)
        self.hour = self.ustamp % 86400 / 3600
        self.minute = self.ustamp % 3600 / 60
        self.second = self.ustamp % 60
    end,
    show_time=function(self)
        return(string.format("%02u:%02u:%02u",self.hour,self.minute,self.second))
    end,
    run=function(self,t,uinterval,sinterval,server)
        if server then self.ntpserver = server end
        self.lastsync = sinterval * 2 * -1  -- force sync on first run
        tmr.alarm(t,uinterval * 1000,1,function()
            self.ustamp = self.ustamp + uinterval
            self:set_time()
            if self.lastsync + sinterval < self.ustamp then
                self:sync()
            end
        end)
    end
})