    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.echo;
    019
    020import java.io.IOException;
    021import java.net.DatagramPacket;
    022import java.net.InetAddress;
    023
    024import org.apache.commons.net.discard.DiscardUDPClient;
    025import org.apache.commons.net.util.NetConstants;
    026
    027/**
    028 * The EchoUDPClient class is a UDP implementation of a client for the Echo protocol described in RFC 862. To use the class, just open a local UDP port with
    029 * {@link org.apache.commons.net.DatagramSocketClient#open open} and call {@link #send send} to send datagrams to the server, then call {@link #receive
    030 * receive } to receive echoes. After you're done echoing data, call {@link org.apache.commons.net.DatagramSocketClient#close close()} to clean up properly.
    031 *
    032 * @see EchoTCPClient
    033 * @see DiscardUDPClient
    034 */
    035
    036public final class EchoUDPClient extends DiscardUDPClient {
    037    /** The default echo port. It is set to 7 according to RFC 862. */
    038    public static final int DEFAULT_PORT = 7;
    039
    040    private final DatagramPacket receivePacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
    041
    042    /**
    043     * Constructs a new instance.
    044     */
    045    public EchoUDPClient() {
    046        // empty
    047    }
    048
    049    /**
    050     * Same as {@code receive(data, data.length)}
    051     *
    052     * @param data the buffer to receive the input
    053     * @return the number of bytes
    054     * @throws IOException on error
    055     */
    056    public int receive(final byte[] data) throws IOException {
    057        return receive(data, data.length);
    058    }
    059
    060    /**
    061     * Receives echoed data and returns its length. The data may be divided up among multiple datagrams, requiring multiple calls to receive. Also, the UDP
    062     * packets will not necessarily arrive in the same order they were sent.
    063     *
    064     * @param data   the buffer to receive the input
    065     * @param length of the buffer
    066     * @return Length of actual data received.
    067     * @throws IOException If an error occurs while receiving the data.
    068     */
    069    public int receive(final byte[] data, final int length) throws IOException {
    070        receivePacket.setData(data);
    071        receivePacket.setLength(length);
    072        checkOpen().receive(receivePacket);
    073        return receivePacket.getLength();
    074    }
    075
    076    /** Same as {@code send(data, data.length, host)} */
    077    @Override
    078    public void send(final byte[] data, final InetAddress host) throws IOException {
    079        send(data, data.length, host, DEFAULT_PORT);
    080    }
    081
    082    /**
    083     * Sends the specified data to the specified server at the default echo port.
    084     *
    085     * @param data   The echo data to send.
    086     * @param length The length of the data to send. Should be less than or equal to the length of the data byte array.
    087     * @param host   The address of the server.
    088     * @throws IOException If an error occurs during the datagram send operation.
    089     */
    090    @Override
    091    public void send(final byte[] data, final int length, final InetAddress host) throws IOException {
    092        send(data, length, host, DEFAULT_PORT);
    093    }
    094
    095}