CharGenUDPClient.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.chargen;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import org.apache.commons.net.DatagramSocketClient;
import org.apache.commons.net.util.NetConstants;
/**
* The CharGenUDPClient class is a UDP implementation of a client for the character generator protocol described in RFC 864. It can also be used for Systat (RFC
* 866), Quote of the Day (RFC 865), and netstat (port 15). All of these protocols involve sending a datagram to the appropriate port, and reading data
* contained in one or more reply datagrams. The chargen and quote of the day protocols only send one reply datagram containing 512 bytes or fewer. The
* other protocols may reply with more than one datagram, in which case you must wait for a timeout to determine that all reply datagrams have been sent.
* <p>
* To use the CharGenUDPClient class, just open a local UDP port with {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #send send
* } to send the datagram that will initiate the data reply. For chargen or quote of the day, just call {@link #receive receive }, and you're done. For netstat
* and systat, call receive in a while loop, and catch a SocketException and InterruptedIOException to detect a timeout (don't forget to set the timeout
* duration beforehand). Don't forget to call {@link org.apache.commons.net.DatagramSocketClient#close close() } to clean up properly.
*
* @see CharGenTCPClient
*/
public final class CharGenUDPClient extends DatagramSocketClient {
/** The systat port value of 11 according to RFC 866. */
public static final int SYSTAT_PORT = 11;
/** The netstat port value of 19. */
public static final int NETSTAT_PORT = 15;
/** The quote of the day port value of 17 according to RFC 865. */
public static final int QUOTE_OF_DAY_PORT = 17;
/** The character generator port value of 19 according to RFC 864. */
public static final int CHARGEN_PORT = 19;
/** The default chargen port. It is set to 19 according to RFC 864. */
public static final int DEFAULT_PORT = 19;
private final byte[] receiveData;
private final DatagramPacket receivePacket;
private final DatagramPacket sendPacket;
/**
* The default CharGenUDPClient constructor. It initializes some internal data structures for sending and receiving the necessary datagrams for the chargen
* and related protocols.
*/
public CharGenUDPClient() {
// CharGen return packets have a maximum length of 512
receiveData = new byte[512];
receivePacket = new DatagramPacket(receiveData, receiveData.length);
sendPacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
}
/**
* Receive the reply data from the server. This will always be 512 bytes or fewer. Chargen and quote of the day only return one packet. Netstat and systat
* require multiple calls to receive() with timeout detection.
*
* @return The reply data from the server.
* @throws IOException If an error occurs while receiving the datagram.
*/
public byte[] receive() throws IOException {
final int length;
final byte[] result;
checkOpen().receive(receivePacket);
result = new byte[length = receivePacket.getLength()];
System.arraycopy(receiveData, 0, result, 0, length);
return result;
}
/**
* Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code>
*
* @param host the destination host
* @throws IOException on error
*/
public void send(final InetAddress host) throws IOException {
send(host, DEFAULT_PORT);
}
/**
* Sends the data initiation datagram. This data in the packet is ignored by the server, and merely serves to signal that the server should send its reply.
*
* @param host The address of the server.
* @param port The port of the service.
* @throws IOException If an error occurs while sending the datagram.
*/
public void send(final InetAddress host, final int port) throws IOException {
sendPacket.setAddress(host);
sendPacket.setPort(port);
checkOpen().send(sendPacket);
}
}