88 lines
2.6 KiB
Java
88 lines
2.6 KiB
Java
|
/* LoRaWAN Timeserver
|
||
|
|
|
||
|
|
construct 7 byte timesync_answer from gateway timestamp and node's time_sync_req
|
||
|
|
|
||
|
|
byte meaning
|
||
|
|
1 sequence number (taken from node's time_sync_req)
|
||
|
|
2 timezone in 15 minutes steps
|
||
|
|
3..6 current second (from epoch time 1970)
|
||
|
|
7 1/250ths fractions of current second
|
||
|
|
|
||
|
|
*/
|
||
|
|
|
||
|
|
function timecompare(a, b) {
|
||
|
|
|
||
|
|
const timeA = a.time;
|
||
|
|
const timeB = b.time;
|
||
|
|
|
||
|
|
let comparison = 0;
|
||
|
|
if (timeA > timeB) {
|
||
|
|
comparison = 1;
|
||
|
|
} else if (timeA < timeB) {
|
||
|
|
comparison = -1;
|
||
|
|
}
|
||
|
|
return comparison;
|
||
|
|
}
|
||
|
|
|
||
|
|
let confidence = 2000; // max millisecond diff gateway time to server time
|
||
|
|
|
||
|
|
// guess if we have received a valid time_sync_req command
|
||
|
|
if (msg.payload.payload_raw.length != 1)
|
||
|
|
return;
|
||
|
|
|
||
|
|
var deviceMsg = { payload: msg.payload.dev_id };
|
||
|
|
var seqNo = msg.payload.payload_raw[0];
|
||
|
|
var seqNoMsg = { payload: seqNo };
|
||
|
|
var gateway_list = msg.payload.metadata.gateways;
|
||
|
|
|
||
|
|
// filter all gateway timestamps that have milliseconds part (which we assume have a ".")
|
||
|
|
var gateways = gateway_list.filter(function (element) {
|
||
|
|
return (element.time.includes("."));
|
||
|
|
});
|
||
|
|
|
||
|
|
var gateway_time = gateways.map(gw => {
|
||
|
|
return {
|
||
|
|
time: new Date(gw.time),
|
||
|
|
eui: gw.gtw_id,
|
||
|
|
}
|
||
|
|
});
|
||
|
|
var server_time = new Date(msg.payload.metadata.time);
|
||
|
|
|
||
|
|
// validate all gateway timestamps against lorawan server_time (which is assumed to be recent)
|
||
|
|
var gw_timestamps = gateway_time.filter(function (element) {
|
||
|
|
return ((element.time > (server_time - confidence) && element.time <= server_time));
|
||
|
|
});
|
||
|
|
|
||
|
|
// if no timestamp left, we have no valid one and exit
|
||
|
|
if (gw_timestamps.length === 0) {
|
||
|
|
var notavailMsg = { payload: "n/a" };
|
||
|
|
var notimeMsg = { payload: 0xff };
|
||
|
|
var buf2 = Buffer.alloc(1);
|
||
|
|
msg.payload = new Buffer(buf2.fill(0xff));
|
||
|
|
msg.port = 9; // Paxcounter TIMEPORT
|
||
|
|
return [notavailMsg, notavailMsg, deviceMsg, seqNoMsg, msg];}
|
||
|
|
|
||
|
|
// sort time array in ascending order to find most recent timestamp for time answer
|
||
|
|
gw_timestamps.sort(timecompare);
|
||
|
|
|
||
|
|
var timestamp = gw_timestamps[0].time;
|
||
|
|
var eui = gw_timestamps[0].eui;
|
||
|
|
var offset = server_time - timestamp;
|
||
|
|
|
||
|
|
var seconds = Math.floor(timestamp/1000);
|
||
|
|
var fractions = (timestamp % 1000) / 4;
|
||
|
|
|
||
|
|
let buf = new ArrayBuffer(7);
|
||
|
|
new DataView(buf).setUint8(0, seqNo);
|
||
|
|
// Timezone (in 15min steps)
|
||
|
|
var timezone = 8; // CET = UTC+2h
|
||
|
|
new DataView(buf).setUint8(1, timezone);
|
||
|
|
new DataView(buf).setUint32(2, seconds);
|
||
|
|
new DataView(buf).setUint8(6, fractions);
|
||
|
|
|
||
|
|
msg.payload = new Buffer(new Uint8Array(buf));
|
||
|
|
msg.port = 9; // Paxcounter TIMEPORT
|
||
|
|
var euiMsg = { payload: eui };
|
||
|
|
var offsetMsg = { payload: offset };
|
||
|
|
|
||
|
|
return [euiMsg, offsetMsg, deviceMsg, seqNoMsg, msg];
|