001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.time;
019
020import java.io.DataInputStream;
021import java.io.IOException;
022import java.util.Date;
023
024import org.apache.commons.net.SocketClient;
025
026/**
027 * The TimeTCPClient class is a TCP implementation of a client for the Time protocol described in RFC 868. To use the class, merely establish a connection with
028 * {@link org.apache.commons.net.SocketClient#connect connect} and call either {@link #getTime getTime()} or {@link #getDate getDate()} to retrieve the time,
029 * then call {@link org.apache.commons.net.SocketClient#disconnect disconnect} to close the connection properly.
030 *
031 *
032 * @see TimeUDPClient
033 */
034
035public final class TimeTCPClient extends SocketClient {
036
037    /** The default time port. It is set to 37 according to RFC 868. */
038    public static final int DEFAULT_PORT = 37;
039
040    /**
041     * The number of seconds between 00:00 1 January 1900 and 00:00 1 January 1970. This value can be useful for converting time values to other formats.
042     */
043    public static final long SECONDS_1900_TO_1970 = 2208988800L;
044
045    /**
046     * The default TimeTCPClient constructor. It merely sets the default port to {@code DEFAULT_PORT}.
047     */
048    public TimeTCPClient() {
049        setDefaultPort(DEFAULT_PORT);
050    }
051
052    /**
053     * Gets the time from the server and returns a Java Date containing the time converted to the local time zone.
054     * <p>
055     * The server will have closed the connection at this point, so you should call {@link org.apache.commons.net.SocketClient#disconnect disconnect} after
056     * calling this method. To retrieve another time, you must initiate another connection with {@link org.apache.commons.net.SocketClient#connect connect}
057     * before calling {@code getDate()} again.
058     * </p>
059     *
060     * @return A Date value containing the time retrieved from the server converted to the local time zone.
061     * @throws IOException If an error occurs while fetching the time.
062     */
063    public Date getDate() throws IOException {
064        return new Date((getTime() - SECONDS_1900_TO_1970) * 1000L);
065    }
066
067    /**
068     * Gets the time from the server and returns it. The time is the number of seconds since 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868.
069     * This method reads the raw 32-bit big-endian unsigned integer from the server, converts it to a Java long, and returns the value.
070     * <p>
071     * The server will have closed the connection at this point, so you should call {@link org.apache.commons.net.SocketClient#disconnect disconnect} after
072     * calling this method. To retrieve another time, you must initiate another connection with {@link org.apache.commons.net.SocketClient#connect connect}
073     * before calling {@code getTime()} again.
074     * </p>
075     *
076     * @return The time value retrieved from the server.
077     * @throws IOException If an error occurs while fetching the time.
078     */
079    public long getTime() throws IOException {
080        final DataInputStream input;
081        input = new DataInputStream(_input_);
082        return input.readInt() & 0xffffffffL;
083    }
084
085}