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NTP client, GPLed

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This commit is contained in:
jrandom
2004-05-02 04:18:53 +00:00
committed by zzz
parent 74209e2607
commit 68a21f1fbb
4 changed files with 733 additions and 0 deletions
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41
apps/time/java/build.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project basedir="." default="all" name="time">
<target name="all" depends="clean, build" />
<target name="build" depends="builddep, jar" />
<target name="builddep">
<ant dir="../../../core/java/" target="build" />
</target>
<target name="compile">
<mkdir dir="./build" />
<mkdir dir="./build/obj" />
<javac srcdir="./src" debug="true" destdir="./build/obj" includes="**/*.java" classpath="../../../core/java/build/i2p.jar" />
</target>
<target name="jar" depends="compile">
<jar destfile="./build/timestamper.jar" basedir="./build/obj" includes="**/*.class">
<manifest>
<attribute name="Main-Class" value="net.i2p.time.Timestamper" />
<attribute name="Class-Path" value="i2p.jar timestamper.jar" />
</manifest>
</jar>
</target>
<target name="javadoc">
<mkdir dir="./build" />
<mkdir dir="./build/javadoc" />
<javadoc
sourcepath="./src:../../../core/java/src:../../../core/java/test" destdir="./build/javadoc"
packagenames="*"
use="true"
access="package"
splitindex="true"
windowtitle="I2P timestamper" />
</target>
<target name="clean">
<delete dir="./build" />
</target>
<target name="cleandep" depends="clean">
<ant dir="../../../core/java/" target="cleandep" />
</target>
<target name="distclean" depends="clean">
<ant dir="../../../core/java/" target="distclean" />
</target>
</project>

138
apps/time/java/src/net/i2p/time/NtpClient.java Normal file
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package net.i2p.time;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.text.DecimalFormat;
/**
* NtpClient - an NTP client for Java. This program connects to an NTP server
* and prints the response to the console.
*
* The local clock offset calculation is implemented according to the SNTP
* algorithm specified in RFC 2030.
*
* Note that on windows platforms, the curent time-of-day timestamp is limited
* to an resolution of 10ms and adversely affects the accuracy of the results.
*
*
* This code is copyright (c) Adam Buckley 2004
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version. A HTML version of the GNU General Public License can be
* seen at http://www.gnu.org/licenses/gpl.html
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* @author Adam Buckley
* (minor refactoring by jrandom)
*/
public class NtpClient {
/** difference between the unix epoch and jan 1 1900 (NTP uses that) */
private final static double SECONDS_1900_TO_EPOCH = 2208988800.0;
private final static int NTP_PORT = 123;
/**
* Query the ntp servers, returning the current time from first one we find
*
* @return milliseconds since january 1, 1970 (UTC)
* @throws IllegalArgumentException if none of the servers are reachable
*/
public static long currentTime(String serverNames[]) {
if (serverNames == null)
throw new IllegalArgumentException("No NTP servers specified");
for (int i = 0; i < serverNames.length; i++) {
long now = currentTime(serverNames[i]);
if (now > 0)
return now;
}
throw new IllegalArgumentException("No reachable NTP servers specified");
}
/**
* Query the given NTP server, returning the current internet time
*
* @return milliseconds since january 1, 1970 (UTC), or -1 on error
*/
public static long currentTime(String serverName) {
try {
// Send request
DatagramSocket socket = new DatagramSocket();
InetAddress address = InetAddress.getByName(serverName);
byte[] buf = new NtpMessage().toByteArray();
DatagramPacket packet = new DatagramPacket(buf, buf.length, address, NTP_PORT);
// Set the transmit timestamp *just* before sending the packet
// ToDo: Does this actually improve performance or not?
NtpMessage.encodeTimestamp(packet.getData(), 40,
(System.currentTimeMillis()/1000.0)
+ SECONDS_1900_TO_EPOCH);
socket.send(packet);
// Get response
packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);
// Immediately record the incoming timestamp
double destinationTimestamp = (System.currentTimeMillis()/1000.0) + SECONDS_1900_TO_EPOCH;
// Process response
NtpMessage msg = new NtpMessage(packet.getData());
double roundTripDelay = (destinationTimestamp-msg.originateTimestamp) -
(msg.receiveTimestamp-msg.transmitTimestamp);
double localClockOffset = ((msg.receiveTimestamp - msg.originateTimestamp) +
(msg.transmitTimestamp - destinationTimestamp)) / 2;
socket.close();
//System.out.println("host: " + serverName + " rtt: " + roundTripDelay + " offset: " + localClockOffset + " seconds");
return (long)(System.currentTimeMillis() + localClockOffset*1000);
} catch (IOException ioe) {
ioe.printStackTrace();
return -1;
}
}
public static void main(String[] args) throws IOException {
// Process command-line args
if(args.length <= 0) {
printUsage();
return;
// args = new String[] { "ntp1.sth.netnod.se", "ntp2.sth.netnod.se" };
}
long now = currentTime(args);
System.out.println("Current time: " + new java.util.Date(now));
}
/**
* Prints usage
*/
static void printUsage() {
System.out.println(
"NtpClient - an NTP client for Java.\n" +
"\n" +
"This program connects to an NTP server and prints the current time to the console.\n" +
"\n" +
"\n" +
"Usage: java NtpClient server[ server]*\n" +
"\n" +
"\n" +
"This program is copyright (c) Adam Buckley 2004 and distributed under the terms\n" +
"of the GNU General Public License. This program is distributed in the hope\n" +
"that it will be useful, but WITHOUT ANY WARRANTY; without even the implied\n" +
"warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU\n" +
"General Public License available at http://www.gnu.org/licenses/gpl.html for\n" +
"more details.");
}
}

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apps/time/java/src/net/i2p/time/NtpMessage.java Normal file
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package net.i2p.time;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
* This class represents a NTP message, as specified in RFC 2030. The message
* format is compatible with all versions of NTP and SNTP.
*
* This class does not support the optional authentication protocol, and
* ignores the key ID and message digest fields.
*
* For convenience, this class exposes message values as native Java types, not
* the NTP-specified data formats. For example, timestamps are
* stored as doubles (as opposed to the NTP unsigned 64-bit fixed point
* format).
*
* However, the contructor NtpMessage(byte[]) and the method toByteArray()
* allow the import and export of the raw NTP message format.
*
*
* Usage example
*
* // Send message
* DatagramSocket socket = new DatagramSocket();
* InetAddress address = InetAddress.getByName("ntp.cais.rnp.br");
* byte[] buf = new NtpMessage().toByteArray();
* DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 123);
* socket.send(packet);
*
* // Get response
* socket.receive(packet);
* System.out.println(msg.toString());
*
*
* This code is copyright (c) Adam Buckley 2004
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version. A HTML version of the GNU General Public License can be
* seen at http://www.gnu.org/licenses/gpl.html
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
*
* Comments for member variables are taken from RFC2030 by David Mills,
* University of Delaware.
*
* Number format conversion code in NtpMessage(byte[] array) and toByteArray()
* inspired by http://www.pps.jussieu.fr/~jch/enseignement/reseaux/
* NTPMessage.java which is copyright (c) 2003 by Juliusz Chroboczek
*
* @author Adam Buckley
*/
public class NtpMessage {
/**
* This is a two-bit code warning of an impending leap second to be
* inserted/deleted in the last minute of the current day. It's values
* may be as follows:
*
* Value Meaning
* ----- -------
* 0 no warning
* 1 last minute has 61 seconds
* 2 last minute has 59 seconds)
* 3 alarm condition (clock not synchronized)
*/
public byte leapIndicator = 0;
/**
* This value indicates the NTP/SNTP version number. The version number
* is 3 for Version 3 (IPv4 only) and 4 for Version 4 (IPv4, IPv6 and OSI).
* If necessary to distinguish between IPv4, IPv6 and OSI, the
* encapsulating context must be inspected.
*/
public byte version = 3;
/**
* This value indicates the mode, with values defined as follows:
*
* Mode Meaning
* ---- -------
* 0 reserved
* 1 symmetric active
* 2 symmetric passive
* 3 client
* 4 server
* 5 broadcast
* 6 reserved for NTP control message
* 7 reserved for private use
*
* In unicast and anycast modes, the client sets this field to 3 (client)
* in the request and the server sets it to 4 (server) in the reply. In
* multicast mode, the server sets this field to 5 (broadcast).
*/
public byte mode = 0;
/**
* This value indicates the stratum level of the local clock, with values
* defined as follows:
*
* Stratum Meaning
* ----------------------------------------------
* 0 unspecified or unavailable
* 1 primary reference (e.g., radio clock)
* 2-15 secondary reference (via NTP or SNTP)
* 16-255 reserved
*/
public short stratum = 0;
/**
* This value indicates the maximum interval between successive messages,
* in seconds to the nearest power of two. The values that can appear in
* this field presently range from 4 (16 s) to 14 (16284 s); however, most
* applications use only the sub-range 6 (64 s) to 10 (1024 s).
*/
public byte pollInterval = 0;
/**
* This value indicates the precision of the local clock, in seconds to
* the nearest power of two. The values that normally appear in this field
* range from -6 for mains-frequency clocks to -20 for microsecond clocks
* found in some workstations.
*/
public byte precision = 0;
/**
* This value indicates the total roundtrip delay to the primary reference
* source, in seconds. Note that this variable can take on both positive
* and negative values, depending on the relative time and frequency
* offsets. The values that normally appear in this field range from
* negative values of a few milliseconds to positive values of several
* hundred milliseconds.
*/
public double rootDelay = 0;
/**
* This value indicates the nominal error relative to the primary reference
* source, in seconds. The values that normally appear in this field
* range from 0 to several hundred milliseconds.
*/
public double rootDispersion = 0;
/**
* This is a 4-byte array identifying the particular reference source.
* In the case of NTP Version 3 or Version 4 stratum-0 (unspecified) or
* stratum-1 (primary) servers, this is a four-character ASCII string, left
* justified and zero padded to 32 bits. In NTP Version 3 secondary
* servers, this is the 32-bit IPv4 address of the reference source. In NTP
* Version 4 secondary servers, this is the low order 32 bits of the latest
* transmit timestamp of the reference source. NTP primary (stratum 1)
* servers should set this field to a code identifying the external
* reference source according to the following list. If the external
* reference is one of those listed, the associated code should be used.
* Codes for sources not listed can be contrived as appropriate.
*
* Code External Reference Source
* ---- -------------------------
* LOCL uncalibrated local clock used as a primary reference for
* a subnet without external means of synchronization
* PPS atomic clock or other pulse-per-second source
* individually calibrated to national standards
* ACTS NIST dialup modem service
* USNO USNO modem service
* PTB PTB (Germany) modem service
* TDF Allouis (France) Radio 164 kHz
* DCF Mainflingen (Germany) Radio 77.5 kHz
* MSF Rugby (UK) Radio 60 kHz
* WWV Ft. Collins (US) Radio 2.5, 5, 10, 15, 20 MHz
* WWVB Boulder (US) Radio 60 kHz
* WWVH Kaui Hawaii (US) Radio 2.5, 5, 10, 15 MHz
* CHU Ottawa (Canada) Radio 3330, 7335, 14670 kHz
* LORC LORAN-C radionavigation system
* OMEG OMEGA radionavigation system
* GPS Global Positioning Service
* GOES Geostationary Orbit Environment Satellite
*/
public byte[] referenceIdentifier = {0, 0, 0, 0};
/**
* This is the time at which the local clock was last set or corrected, in
* seconds since 00:00 1-Jan-1900.
*/
public double referenceTimestamp = 0;
/**
* This is the time at which the request departed the client for the
* server, in seconds since 00:00 1-Jan-1900.
*/
public double originateTimestamp = 0;
/**
* This is the time at which the request arrived at the server, in seconds
* since 00:00 1-Jan-1900.
*/
public double receiveTimestamp = 0;
/**
* This is the time at which the reply departed the server for the client,
* in seconds since 00:00 1-Jan-1900.
*/
public double transmitTimestamp = 0;
/**
* Constructs a new NtpMessage from an array of bytes.
*/
public NtpMessage(byte[] array) {
// See the packet format diagram in RFC 2030 for details
leapIndicator = (byte) ((array[0] >> 6) & 0x3);
version = (byte) ((array[0] >> 3) & 0x7);
mode = (byte) (array[0] & 0x7);
stratum = unsignedByteToShort(array[1]);
pollInterval = array[2];
precision = array[3];
rootDelay = (array[4] * 256.0) +
unsignedByteToShort(array[5]) +
(unsignedByteToShort(array[6]) / 256.0) +
(unsignedByteToShort(array[7]) / 65536.0);
rootDispersion = (unsignedByteToShort(array[8]) * 256.0) +
unsignedByteToShort(array[9]) +
(unsignedByteToShort(array[10]) / 256.0) +
(unsignedByteToShort(array[11]) / 65536.0);
referenceIdentifier[0] = array[12];
referenceIdentifier[1] = array[13];
referenceIdentifier[2] = array[14];
referenceIdentifier[3] = array[15];
referenceTimestamp = decodeTimestamp(array, 16);
originateTimestamp = decodeTimestamp(array, 24);
receiveTimestamp = decodeTimestamp(array, 32);
transmitTimestamp = decodeTimestamp(array, 40);
}
/**
* Constructs a new NtpMessage in client -> server mode, and sets the
* transmit timestamp to the current time.
*/
public NtpMessage() {
// Note that all the other member variables are already set with
// appropriate default values.
this.mode = 3;
this.transmitTimestamp = (System.currentTimeMillis()/1000.0) + 2208988800.0;
}
/**
* This method constructs the data bytes of a raw NTP packet.
*/
public byte[] toByteArray() {
// All bytes are automatically set to 0
byte[] p = new byte[48];
p[0] = (byte) (leapIndicator << 6 | version << 3 | mode);
p[1] = (byte) stratum;
p[2] = (byte) pollInterval;
p[3] = (byte) precision;
// root delay is a signed 16.16-bit FP, in Java an int is 32-bits
int l = (int) (rootDelay * 65536.0);
p[4] = (byte) ((l >> 24) & 0xFF);
p[5] = (byte) ((l >> 16) & 0xFF);
p[6] = (byte) ((l >> 8) & 0xFF);
p[7] = (byte) (l & 0xFF);
// root dispersion is an unsigned 16.16-bit FP, in Java there are no
// unsigned primitive types, so we use a long which is 64-bits
long ul = (long) (rootDispersion * 65536.0);
p[8] = (byte) ((ul >> 24) & 0xFF);
p[9] = (byte) ((ul >> 16) & 0xFF);
p[10] = (byte) ((ul >> 8) & 0xFF);
p[11] = (byte) (ul & 0xFF);
p[12] = referenceIdentifier[0];
p[13] = referenceIdentifier[1];
p[14] = referenceIdentifier[2];
p[15] = referenceIdentifier[3];
encodeTimestamp(p, 16, referenceTimestamp);
encodeTimestamp(p, 24, originateTimestamp);
encodeTimestamp(p, 32, receiveTimestamp);
encodeTimestamp(p, 40, transmitTimestamp);
return p;
}
/**
* Returns a string representation of a NtpMessage
*/
public String toString() {
String precisionStr = new DecimalFormat("0.#E0").format(Math.pow(2, precision));
return "Leap indicator: " + leapIndicator + "\n" +
"Version: " + version + "\n" +
"Mode: " + mode + "\n" +
"Stratum: " + stratum + "\n" +
"Poll: " + pollInterval + "\n" +
"Precision: " + precision + " (" + precisionStr + " seconds)\n" +
"Root delay: " + new DecimalFormat("0.00").format(rootDelay*1000) + " ms\n" +
"Root dispersion: " + new DecimalFormat("0.00").format(rootDispersion*1000) + " ms\n" +
"Reference identifier: " + referenceIdentifierToString(referenceIdentifier, stratum, version) + "\n" +
"Reference timestamp: " + timestampToString(referenceTimestamp) + "\n" +
"Originate timestamp: " + timestampToString(originateTimestamp) + "\n" +
"Receive timestamp: " + timestampToString(receiveTimestamp) + "\n" +
"Transmit timestamp: " + timestampToString(transmitTimestamp);
}
/**
* Converts an unsigned byte to a short. By default, Java assumes that
* a byte is signed.
*/
public static short unsignedByteToShort(byte b) {
if((b & 0x80)==0x80)
return (short) (128 + (b & 0x7f));
else
return (short) b;
}
/**
* Will read 8 bytes of a message beginning at <code>pointer</code>
* and return it as a double, according to the NTP 64-bit timestamp
* format.
*/
public static double decodeTimestamp(byte[] array, int pointer) {
double r = 0.0;
for(int i=0; i<8; i++) {
r += unsignedByteToShort(array[pointer+i]) * Math.pow(2, (3-i)*8);
}
return r;
}
/**
* Encodes a timestamp in the specified position in the message
*/
public static void encodeTimestamp(byte[] array, int pointer, double timestamp) {
// Converts a double into a 64-bit fixed point
for(int i=0; i<8; i++) {
// 2^24, 2^16, 2^8, .. 2^-32
double base = Math.pow(2, (3-i)*8);
// Capture byte value
array[pointer+i] = (byte) (timestamp / base);
// Subtract captured value from remaining total
timestamp = timestamp - (double) (unsignedByteToShort(array[pointer+i]) * base);
}
// From RFC 2030: It is advisable to fill the non-significant
// low order bits of the timestamp with a random, unbiased
// bitstring, both to avoid systematic roundoff errors and as
// a means of loop detection and replay detection.
array[7] = (byte) (Math.random()*255.0);
}
/**
* Returns a timestamp (number of seconds since 00:00 1-Jan-1900) as a
* formatted date/time string.
*/
public static String timestampToString(double timestamp) {
if(timestamp==0) return "0";
// timestamp is relative to 1900, utc is used by Java and is relative
// to 1970
double utc = timestamp - (2208988800.0);
// milliseconds
long ms = (long) (utc * 1000.0);
// date/time
String date = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss").format(new Date(ms));
// fraction
double fraction = timestamp - ((long) timestamp);
String fractionSting = new DecimalFormat(".000000").format(fraction);
return date + fractionSting;
}
/**
* Returns a string representation of a reference identifier according
* to the rules set out in RFC 2030.
*/
public static String referenceIdentifierToString(byte[] ref, short stratum, byte version) {
// From the RFC 2030:
// In the case of NTP Version 3 or Version 4 stratum-0 (unspecified)
// or stratum-1 (primary) servers, this is a four-character ASCII
// string, left justified and zero padded to 32 bits.
if(stratum==0 || stratum==1) {
return new String(ref);
}
// In NTP Version 3 secondary servers, this is the 32-bit IPv4
// address of the reference source.
else if(version==3) {
return unsignedByteToShort(ref[0]) + "." +
unsignedByteToShort(ref[1]) + "." +
unsignedByteToShort(ref[2]) + "." +
unsignedByteToShort(ref[3]);
}
// In NTP Version 4 secondary servers, this is the low order 32 bits
// of the latest transmit timestamp of the reference source.
else if(version==4) {
return "" + ((unsignedByteToShort(ref[0]) / 256.0) +
(unsignedByteToShort(ref[1]) / 65536.0) +
(unsignedByteToShort(ref[2]) / 16777216.0) +
(unsignedByteToShort(ref[3]) / 4294967296.0));
}
return "";
}
}

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apps/time/java/src/net/i2p/time/Timestamper.java Normal file
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package net.i2p.time;
import net.i2p.util.Log;
import net.i2p.util.I2PThread;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.net.URL;
import java.net.MalformedURLException;
import java.io.IOException;
/**
* Periodically query a series of NTP servers and post the offset
* to a given URL. It tries the NTP servers in order, contacting them
* using UDP port 123, and sends the current date to the URL specified
* (specifically, URL+"&now=" + yyyyMMdd_HH:mm:ss.SSS in the UK locale).
* It does this every 5 minutes, forever.
*
* Usage: <pre>
* Timestamper URL ntpServer1[ ntpServer2]*
* </pre>
*/
public class Timestamper implements Runnable {
private static Log _log = new Log(Timestamper.class);
private String _targetURL;
private String _serverList[];
private int DELAY_MS = 5*60*1000;
public Timestamper(String url, String serverNames[]) {
if (_log.shouldLog(Log.INFO))
_log.info("Creating new timestamper pointing at " + url);
_targetURL = url;
_serverList = serverNames;
}
public void startTimestamper() {
if (_log.shouldLog(Log.INFO))
_log.info("Starting timestamper pointing at " + _targetURL);
I2PThread t = new I2PThread(this, "Timestamper");
t.setPriority(I2PThread.MIN_PRIORITY);
t.start();
}
public void run() {
if (_log.shouldLog(Log.INFO))
_log.info("Starting up timestamper");
while (true) {
if (_log.shouldLog(Log.DEBUG))
_log.debug("Querying servers " + _serverList);
long now = NtpClient.currentTime(_serverList);
if (now < 0) {
_log.error("Unable to contact any of the NTP servers - network disconnect?");
} else {
if (_log.shouldLog(Log.DEBUG))
_log.debug("Stamp time");
stampTime(now);
}
try { Thread.sleep(DELAY_MS); } catch (InterruptedException ie) {}
}
}
/**
* Send an HTTP request to a given URL specifying the current time
*/
private void stampTime(long now) {
try {
URL url = new URL(_targetURL + "&now=" + getNow(now));
Object o = url.getContent();
// ignore the content
} catch (MalformedURLException mue) {
_log.error("Invalid URL", mue);
} catch (IOException ioe) {
_log.error("Error stamping the time", ioe);
}
}
private SimpleDateFormat _fmt = new SimpleDateFormat("yyyyMMdd_HH:mm:ss.SSS", Locale.UK);
private String getNow(long now) {
synchronized (_fmt) {
return _fmt.format(new Date(now));
}
}
public static void main(String args[]) {
if ( (args == null) || (args.length < 2) ) {
usage();
return;
//args = new String[] { "http://dev.i2p.net:80/somePath?pass=password", "ntp1.sth.netnod.se", "ntp2.sth.netnod.se" };
}
String servers[] = new String[args.length-1];
System.arraycopy(args, 1, servers, 0, servers.length);
Timestamper ts = new Timestamper(args[0], servers);
ts.startTimestamper();
}
private static void usage() {
System.err.println("Usage: Timestamper URL ntpServer[ ntpServer]*");
_log.error("Usage: Timestamper URL ntpServer[ ntpServer]*");
}
}