src/main/java/org/apache/commons/net/echo/EchoUDPClient.java

/*
 * 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.
 */

package org.apache.commons.net.echo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;

import org.apache.commons.net.discard.DiscardUDPClient;
import org.apache.commons.net.util.NetConstants;

/**
 * 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
 * {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #send send } to send datagrams to the server, then call {@link #receive
 * receive } to receive echoes. After you're done echoing data, call {@link org.apache.commons.net.DatagramSocketClient#close close() } to clean up properly.
 *
 * @see EchoTCPClient
 * @see DiscardUDPClient
 */

public final class EchoUDPClient extends DiscardUDPClient {
    /** The default echo port. It is set to 7 according to RFC 862. */
    public static final int DEFAULT_PORT = 7;

    private final DatagramPacket receivePacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);

    /**
     * Same as <code>receive(data, data.length)</code>
     *
     * @param data the buffer to receive the input
     * @return the number of bytes
     * @throws IOException on error
     */
    public int receive(final byte[] data) throws IOException {
        return receive(data, data.length);
    }

    /**
     * Receives echoed data and returns its length. The data may be divided up among multiple datagrams, requiring multiple calls to receive. Also, the UDP
     * packets will not necessarily arrive in the same order they were sent.
     *
     * @param data   the buffer to receive the input
     * @param length of the buffer
     *
     * @return Length of actual data received.
     * @throws IOException If an error occurs while receiving the data.
     */
    public int receive(final byte[] data, final int length) throws IOException {
        receivePacket.setData(data);
        receivePacket.setLength(length);
        checkOpen().receive(receivePacket);
        return receivePacket.getLength();
    }

    /** Same as <code>send(data, data.length, host)</code> */
    @Override
    public void send(final byte[] data, final InetAddress host) throws IOException {
        send(data, data.length, host, DEFAULT_PORT);
    }

    /**
     * Sends the specified data to the specified server at the default echo port.
     *
     * @param data   The echo data to send.
     * @param length The length of the data to send. Should be less than or equal to the length of the data byte array.
     * @param host   The address of the server.
     * @throws IOException If an error occurs during the datagram send operation.
     */
    @Override
    public void send(final byte[] data, final int length, final InetAddress host) throws IOException {
        send(data, length, host, DEFAULT_PORT);
    }

}