commons-net.jar Source Code

commons-net.jar is the bytecode of Apache Commons Net library, which implements the client side of many basic Internet protocols.

Apache Commons Net Source Code files are provided in the binary packge (commons-net-3.8.0-bin.zip). You can download it at Apache Commons Net Website.

The source code of commons-net-3.8.0.jar is provided below:

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org/apache/commons/net/ntp/TimeInfo.java

package org.apache.commons.net.ntp;
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


import java.net.DatagramPacket;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.List;

/**
 * Wrapper class to network time packet messages (NTP, etc) that computes
 * related timing info and stats.
 */
public class TimeInfo {

    private final NtpV3Packet message;
    private List<String> comments;
    private Long delayMillis;
    private Long offsetMillis;

    /**
     * time at which time message packet was received by local machine
     */
    private final long returnTimeMillis;

    /**
     * flag indicating that the TimeInfo details was processed and delay/offset were computed
     */
    private boolean detailsComputed;

    /**
     * Create TimeInfo object with raw packet message and destination time received.
     *
     * @param message NTP message packet
     * @param returnTimeMillis  destination receive time
     * @throws IllegalArgumentException if message is null
     */
    public TimeInfo(final NtpV3Packet message, final long returnTimeMillis) {
        this(message, returnTimeMillis, null, true);
    }

    /**
     * Create TimeInfo object with raw packet message and destination time received.
     *
     * @param message NTP message packet
     * @param returnTimeMillis  destination receive time
     * @param comments List of errors/warnings identified during processing
     * @throws IllegalArgumentException if message is null
     */
    public TimeInfo(final NtpV3Packet message, final long returnTimeMillis, final List<String> comments)
    {
            this(message, returnTimeMillis, comments, true);
    }

    /**
     * Create TimeInfo object with raw packet message and destination time received.
     * Auto-computes details if computeDetails flag set otherwise this is delayed
     * until computeDetails() is called. Delayed computation is for fast
     * intialization when sub-millisecond timing is needed.
     *
     * @param msgPacket NTP message packet
     * @param returnTimeMillis  destination receive time
     * @param doComputeDetails  flag to pre-compute delay/offset values
     * @throws IllegalArgumentException if message is null
     */
    public TimeInfo(final NtpV3Packet msgPacket, final long returnTimeMillis, final boolean doComputeDetails)
    {
            this(msgPacket, returnTimeMillis, null, doComputeDetails);
    }

    /**
     * Create TimeInfo object with raw packet message and destination time received.
     * Auto-computes details if computeDetails flag set otherwise this is delayed
     * until computeDetails() is called. Delayed computation is for fast
     * intialization when sub-millisecond timing is needed.
     *
     * @param message NTP message packet
     * @param returnTimeMillis  destination receive time
     * @param comments  list of comments used to store errors/warnings with message
     * @param doComputeDetails  flag to pre-compute delay/offset values
     * @throws IllegalArgumentException if message is null
     */
    public TimeInfo(final NtpV3Packet message, final long returnTimeMillis, final List<String> comments,
                   final boolean doComputeDetails)
    {
        if (message == null) {
            throw new IllegalArgumentException("message cannot be null");
        }
        this.returnTimeMillis = returnTimeMillis;
        this.message = message;
        this.comments = comments;
        if (doComputeDetails) {
            computeDetails();
        }
    }

    /**
     * Add comment (error/warning) to list of comments associated
     * with processing of NTP parameters. If comment list not create
     * then one will be created.
     *
     * @param comment the comment
     */
    public void addComment(final String comment)
    {
        if (comments == null) {
            comments = new ArrayList<>();
        }
        comments.add(comment);
    }

    /**
     * Compute and validate details of the NTP message packet. Computed
     * fields include the offset and delay.
     */
    public void computeDetails()
    {
        if (detailsComputed) {
            return; // details already computed - do nothing
        }
        detailsComputed = true;
        if (comments == null) {
            comments = new ArrayList<>();
        }

        final TimeStamp origNtpTime = message.getOriginateTimeStamp();
        final long origTimeMillis = origNtpTime.getTime();

        // Receive Time is time request received by server (t2)
        final TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
        final long rcvTimeMillis = rcvNtpTime.getTime();

        // Transmit time is time reply sent by server (t3)
        final TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
        final long xmitTimeMillis = xmitNtpTime.getTime();

        /*
         * Round-trip network delay and local clock offset (or time drift) is calculated
         * according to this standard NTP equation:
         *
         * LocalClockOffset = ((ReceiveTimestamp - OriginateTimestamp) +
         *                     (TransmitTimestamp - DestinationTimestamp)) / 2
         *
         * equations from RFC-1305 (NTPv3)
         *      roundtrip delay = (t4 - t1) - (t3 - t2)
         *      local clock offset = ((t2 - t1) + (t3 - t4)) / 2
         *
         * It takes into account network delays and assumes that they are symmetrical.
         *
         * Note the typo in SNTP RFCs 1769/2030 which state that the delay
         * is (T4 - T1) - (T2 - T3) with the "T2" and "T3" switched.
         */
        if (origNtpTime.ntpValue() == 0)
        {
            // without originate time cannot determine when packet went out
            // might be via a broadcast NTP packet...
            if (xmitNtpTime.ntpValue() != 0)
            {
                offsetMillis = Long.valueOf(xmitTimeMillis - returnTimeMillis);
                comments.add("Error: zero orig time -- cannot compute delay");
            } else {
                comments.add("Error: zero orig time -- cannot compute delay/offset");
            }
        } else if (rcvNtpTime.ntpValue() == 0 || xmitNtpTime.ntpValue() == 0) {
            comments.add("Warning: zero rcvNtpTime or xmitNtpTime");
            // assert destTime >= origTime since network delay cannot be negative
            if (origTimeMillis > returnTimeMillis) {
                comments.add("Error: OrigTime > DestRcvTime");
            } else {
                // without receive or xmit time cannot figure out processing time
                // so delay is simply the network travel time
                delayMillis = Long.valueOf(returnTimeMillis - origTimeMillis);
            }
            // TODO: is offset still valid if rcvNtpTime=0 || xmitNtpTime=0 ???
            // Could always hash origNtpTime (sendTime) but if host doesn't set it
            // then it's an malformed ntp host anyway and we don't care?
            // If server is in broadcast mode then we never send out a query in first place...
            if (rcvNtpTime.ntpValue() != 0)
            {
                // xmitTime is 0 just use rcv time
                offsetMillis = Long.valueOf(rcvTimeMillis - origTimeMillis);
            } else if (xmitNtpTime.ntpValue() != 0)
            {
                // rcvTime is 0 just use xmitTime time
                offsetMillis = Long.valueOf(xmitTimeMillis - returnTimeMillis);
            }
        } else
        {
             long delayValueMillis = returnTimeMillis - origTimeMillis;
             // assert xmitTime >= rcvTime: difference typically < 1ms
             if (xmitTimeMillis < rcvTimeMillis)
             {
                 // server cannot send out a packet before receiving it...
                 comments.add("Error: xmitTime < rcvTime"); // time-travel not allowed
             } else
             {
                 // subtract processing time from round-trip network delay
                 final long deltaMillis = xmitTimeMillis - rcvTimeMillis;
                 // in normal cases the processing delta is less than
                 // the total roundtrip network travel time.
                 if (deltaMillis <= delayValueMillis)
                 {
                     delayValueMillis -= deltaMillis; // delay = (t4 - t1) - (t3 - t2)
                 } else
                 {
                     // if delta - delayValue == 1 ms then it's a round-off error
                     // e.g. delay=3ms, processing=4ms
                     if (deltaMillis - delayValueMillis == 1)
                     {
                         // delayValue == 0 -> local clock saw no tick change but destination clock did
                         if (delayValueMillis != 0)
                         {
                             comments.add("Info: processing time > total network time by 1 ms -> assume zero delay");
                             delayValueMillis = 0;
                         }
                     } else {
                        comments.add("Warning: processing time > total network time");
                    }
                 }
             }
             delayMillis = Long.valueOf(delayValueMillis);
            if (origTimeMillis > returnTimeMillis) {
                comments.add("Error: OrigTime > DestRcvTime");
            }

            offsetMillis = Long.valueOf(((rcvTimeMillis - origTimeMillis) + (xmitTimeMillis - returnTimeMillis)) / 2);
        }
    }

    /**
     * Return list of comments (if any) during processing of NTP packet.
     *
     * @return List or null if not yet computed
     */
    public List<String> getComments()
    {
        return comments;
    }

    /**
     * Get round-trip network delay. If null then could not compute the delay.
     *
     * @return Long or null if delay not available.
     */
    public Long getDelay()
    {
        return delayMillis;
    }

    /**
     * Get clock offset needed to adjust local clock to match remote clock. If null then could not
     * compute the offset.
     *
     * @return Long or null if offset not available.
     */
    public Long getOffset()
    {
        return offsetMillis;
    }

    /**
     * Returns NTP message packet.
     *
     * @return NTP message packet.
     */
    public NtpV3Packet getMessage()
    {
        return message;
    }

    /**
     * Get host address from message datagram if available
     * @return host address of available otherwise null
     * @since 3.4
     */
    public InetAddress getAddress() {
        final DatagramPacket pkt = message.getDatagramPacket();
        return pkt == null ? null : pkt.getAddress();
    }

    /**
     * Returns time at which time message packet was received by local machine.
     *
     * @return packet return time.
     */
    public long getReturnTime()
    {
        return returnTimeMillis;
    }

    /**
     * Compares this object against the specified object.
     * The result is <code>true</code> if and only if the argument is
     * not <code>null</code> and is a <code>TimeStamp</code> object that
     * contains the same values as this object.
     *
     * @param   obj   the object to compare with.
     * @return  <code>true</code> if the objects are the same;
     *          <code>false</code> otherwise.
     * @since 3.4
     */
    @Override
    public boolean equals(final Object obj)
    {
        if (this == obj) {
            return true;
        }
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        final TimeInfo other = (TimeInfo) obj;
        return returnTimeMillis == other.returnTimeMillis && message.equals(other.message);
    }

    /**
     * Computes a hashcode for this object. The result is the exclusive
     * OR of the return time and the message hash code.
     *
     * @return  a hash code value for this object.
     * @since 3.4
     */
    @Override
    public int hashCode()
    {
        final int prime = 31;
        int result = (int)returnTimeMillis;
        result = prime * result + message.hashCode();
        return result;
    }

}

org/apache/commons/net/ntp/TimeInfo.java

 

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