    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
    038    /** The default echo port. It is set to 7 according to RFC 862. */
    039    public static final int DEFAULT_PORT = 7;
    040
    041    private final DatagramPacket receivePacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
    042
    043    /**
    044     * Constructs a new instance.
    045     */
    046    public EchoUDPClient() {
    047        // empty
    048    }
    049
    050    /**
    051     * Same as {@code receive(data, data.length)}
    052     *
    053     * @param data the buffer to receive the input
    054     * @return the number of bytes
    055     * @throws IOException on error
    056     */
    057    public int receive(final byte[] data) throws IOException {
    058        return receive(data, data.length);
    059    }
    060
    061    /**
    062     * Receives echoed data and returns its length. The data may be divided up among multiple datagrams, requiring multiple calls to receive. Also, the UDP
    063     * packets will not necessarily arrive in the same order they were sent.
    064     *
    065     * @param data   the buffer to receive the input
    066     * @param length of the buffer
    067     * @return Length of actual data received.
    068     * @throws IOException If an error occurs while receiving the data.
    069     */
    070    public int receive(final byte[] data, final int length) throws IOException {
    071        receivePacket.setData(data);
    072        receivePacket.setLength(length);
    073        checkOpen().receive(receivePacket);
    074        return receivePacket.getLength();
    075    }
    076
    077    /** Same as {@code send(data, data.length, host)} */
    078    @Override
    079    public void send(final byte[] data, final InetAddress host) throws IOException {
    080        send(data, data.length, host, DEFAULT_PORT);
    081    }
    082
    083    /**
    084     * Sends the specified data to the specified server at the default echo port.
    085     *
    086     * @param data   The echo data to send.
    087     * @param length The length of the data to send. Should be less than or equal to the length of the data byte array.
    088     * @param host   The address of the server.
    089     * @throws IOException If an error occurs during the datagram send operation.
    090     */
    091    @Override
    092    public void send(final byte[] data, final int length, final InetAddress host) throws IOException {
    093        send(data, length, host, DEFAULT_PORT);
    094    }
    095
    096}