    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 *      http://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     * Same as <code> receive(data, data.length)</code>
    044     *
    045     * @param data the buffer to receive the input
    046     * @return the number of bytes
    047     * @throws IOException on error
    048     */
    049    public int receive(final byte[] data) throws IOException {
    050        return receive(data, data.length);
    051    }
    052
    053    /**
    054     * Receives echoed data and returns its length. The data may be divided up among multiple datagrams, requiring multiple calls to receive. Also, the UDP
    055     * packets will not necessarily arrive in the same order they were sent.
    056     *
    057     * @param data   the buffer to receive the input
    058     * @param length of the buffer
    059     *
    060     * @return Length of actual data received.
    061     * @throws IOException If an error occurs while receiving the data.
    062     */
    063    public int receive(final byte[] data, final int length) throws IOException {
    064        receivePacket.setData(data);
    065        receivePacket.setLength(length);
    066        checkOpen().receive(receivePacket);
    067        return receivePacket.getLength();
    068    }
    069
    070    /** Same as <code> send(data, data.length, host) </code> */
    071    @Override
    072    public void send(final byte[] data, final InetAddress host) throws IOException {
    073        send(data, data.length, host, DEFAULT_PORT);
    074    }
    075
    076    /**
    077     * Sends the specified data to the specified server at the default echo port.
    078     *
    079     * @param data   The echo data to send.
    080     * @param length The length of the data to send. Should be less than or equal to the length of the data byte array.
    081     * @param host   The address of the server.
    082     * @throws IOException If an error occurs during the datagram send operation.
    083     */
    084    @Override
    085    public void send(final byte[] data, final int length, final InetAddress host) throws IOException {
    086        send(data, length, host, DEFAULT_PORT);
    087    }
    088
    089}