private long getOffset(TimeInfo info) throws SystemTimeManagerException {
NtpV3Packet message = info.getMessage();
logStuff(info, message);
info.computeDetails(); // compute offset/delay if not already done
Long offsetValue = info.getOffset();
Long delayValue = info.getDelay();
log.info("Roundtrip delay=" + delayValue + "ms, clock offset=" + offsetValue + "ms");
if (offsetValue == null) {
throw new SystemTimeManagerException(
"Could not get offset needed to adjust local clock to match remote clock");
} else {
return offsetValue;
}
}
/**
* Queries the given timeserver <code>hostname</code> and returns the time in milliseconds.
*
* @param hostname the timeserver to query
* @return the time in milliseconds or the current time of the system if an error occurs.
*/
protected static long getTime(String hostname) {
try {
NTPUDPClient timeClient = new NTPUDPClient();
timeClient.setDefaultTimeout(NTP_TIMEOUT);
InetAddress inetAddress = InetAddress.getByName(hostname);
TimeInfo timeInfo = timeClient.getTime(inetAddress);
return timeInfo.getReturnTime();
} catch (UnknownHostException uhe) {
logger.warn(
"the given hostname '{}' of the timeserver is unknown -> returning current sytem time instead",
hostname);
} catch (IOException ioe) {
logger.warn(
"couldn't establish network connection [host '{}'] -> returning current sytem time instead",
hostname);
}
return System.currentTimeMillis();
}
private void logStuff(TimeInfo info, NtpV3Packet message) {
if (!log.isDebugEnabled()) {
return;
}
TimeStamp refNtpTime = message.getReferenceTimeStamp();
log.debug("Reference Timestamp:\t" + refNtpTime.toDateString());
// Originate Time is time request sent by client (t1)
TimeStamp origNtpTime = message.getOriginateTimeStamp();
log.debug("Originate Timestamp:\t" + origNtpTime.toDateString());
// Receive Time is time request received by server (t2)
TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
log.debug("Receive Timestamp:\t" + rcvNtpTime.toDateString());
// Transmit time is time reply sent by server (t3)
TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
log.debug("Transmit Timestamp:\t" + xmitNtpTime.toDateString());
// Destination time is time reply received by client (t4)
TimeStamp destNtpTime = TimeStamp.getNtpTime(info.getReturnTime());
log.debug("Destination Timestamp:\t" + destNtpTime.toDateString());
}
/**
* Process <code>TimeInfo</code> object and print its details.
*
* @param info <code>TimeInfo</code> object.
*/
public static void processResponse(TimeInfo info) {
NtpV3Packet message = info.getMessage();
int stratum = message.getStratum();
String refType;
if (stratum <= 0) {
refType = "(Unspecified or Unavailable)";
} else if (stratum == 1) {
refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc.
} else {
refType = "(Secondary Reference; e.g. via NTP or SNTP)";
}
// stratum should be 0..15...
System.out.println(" Stratum: " + stratum + " " + refType);
int version = message.getVersion();
int li = message.getLeapIndicator();
System.out.println(
" leap=" + li + ", version=" + version + ", precision=" + message.getPrecision());
System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")");
int poll = message.getPoll();
// poll value typically btwn MINPOLL (4) and MAXPOLL (14)
System.out.println(
" poll: "
+ (poll <= 0 ? 1 : (int) Math.pow(2, poll))
+ " seconds"
+ " (2 ** "
+ poll
+ ")");
double disp = message.getRootDispersionInMillisDouble();
System.out.println(
" rootdelay="
+ numberFormat.format(message.getRootDelayInMillisDouble())
+ ", rootdispersion(ms): "
+ numberFormat.format(disp));
int refId = message.getReferenceId();
String refAddr = NtpUtils.getHostAddress(refId);
String refName = null;
if (refId != 0) {
if (refAddr.equals("127.127.1.0")) {
refName = "LOCAL"; // This is the ref address for the Local Clock
} else if (stratum >= 2) {
// If reference id has 127.127 prefix then it uses its own reference clock
// defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5
// for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution.
if (!refAddr.startsWith("127.127")) {
try {
InetAddress addr = InetAddress.getByName(refAddr);
String name = addr.getHostName();
if (name != null && !name.equals(refAddr)) {
refName = name;
}
} catch (UnknownHostException e) {
// some stratum-2 servers sync to ref clock device but fudge stratum level higher...
// (e.g. 2)
// ref not valid host maybe it's a reference clock name?
// otherwise just show the ref IP address.
refName = NtpUtils.getReferenceClock(message);
}
}
} else if (version >= 3 && (stratum == 0 || stratum == 1)) {
refName = NtpUtils.getReferenceClock(message);
// refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.)
}
// otherwise give up on naming the beast...
}
if (refName != null && refName.length() > 1) {
refAddr += " (" + refName + ")";
}
System.out.println(" Reference Identifier:\t" + refAddr);
TimeStamp refNtpTime = message.getReferenceTimeStamp();
System.out.println(" Reference Timestamp:\t" + refNtpTime + " " + refNtpTime.toDateString());
// Originate Time is time request sent by client (t1)
TimeStamp origNtpTime = message.getOriginateTimeStamp();
System.out.println(" Originate Timestamp:\t" + origNtpTime + " " + origNtpTime.toDateString());
long destTime = info.getReturnTime();
// Receive Time is time request received by server (t2)
TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " " + rcvNtpTime.toDateString());
// Transmit time is time reply sent by server (t3)
TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " " + xmitNtpTime.toDateString());
// Destination time is time reply received by client (t4)
TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime);
System.out.println(
" Destination Timestamp:\t" + destNtpTime + " " + destNtpTime.toDateString());
info.computeDetails(); // compute offset/delay if not already done
Long offsetValue = info.getOffset();
Long delayValue = info.getDelay();
String delay = (delayValue == null) ? "N/A" : delayValue.toString();
String offset = (offsetValue == null) ? "N/A" : offsetValue.toString();
System.out.println(
" Roundtrip delay(ms)=" + delay + ", clock offset(ms)=" + offset); // offset in ms
}