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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.net.echo;
19  
20  import java.io.IOException;
21  import java.net.DatagramPacket;
22  import java.net.InetAddress;
23  
24  import org.apache.commons.net.discard.DiscardUDPClient;
25  import org.apache.commons.net.util.NetConstants;
26  
27  /**
28   * 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
29   * {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #send send } to send datagrams to the server, then call {@link #receive
30   * receive } to receive echoes. After you're done echoing data, call {@link org.apache.commons.net.DatagramSocketClient#close close() } to clean up properly.
31   *
32   * @see EchoTCPClient
33   * @see DiscardUDPClient
34   */
35  
36  public final class EchoUDPClient extends DiscardUDPClient {
37      /** The default echo port. It is set to 7 according to RFC 862. */
38      public static final int DEFAULT_PORT = 7;
39  
40      private final DatagramPacket receivePacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
41  
42      /**
43       * Same as <code>receive(data, data.length)</code>
44       *
45       * @param data the buffer to receive the input
46       * @return the number of bytes
47       * @throws IOException on error
48       */
49      public int receive(final byte[] data) throws IOException {
50          return receive(data, data.length);
51      }
52  
53      /**
54       * Receives echoed data and returns its length. The data may be divided up among multiple datagrams, requiring multiple calls to receive. Also, the UDP
55       * packets will not necessarily arrive in the same order they were sent.
56       *
57       * @param data   the buffer to receive the input
58       * @param length of the buffer
59       *
60       * @return Length of actual data received.
61       * @throws IOException If an error occurs while receiving the data.
62       */
63      public int receive(final byte[] data, final int length) throws IOException {
64          receivePacket.setData(data);
65          receivePacket.setLength(length);
66          checkOpen().receive(receivePacket);
67          return receivePacket.getLength();
68      }
69  
70      /** Same as <code>send(data, data.length, host)</code> */
71      @Override
72      public void send(final byte[] data, final InetAddress host) throws IOException {
73          send(data, data.length, host, DEFAULT_PORT);
74      }
75  
76      /**
77       * Sends the specified data to the specified server at the default echo port.
78       *
79       * @param data   The echo data to send.
80       * @param length The length of the data to send. Should be less than or equal to the length of the data byte array.
81       * @param host   The address of the server.
82       * @throws IOException If an error occurs during the datagram send operation.
83       */
84      @Override
85      public void send(final byte[] data, final int length, final InetAddress host) throws IOException {
86          send(data, length, host, DEFAULT_PORT);
87      }
88  
89  }