org.apache.commons.net.chargen.CharGenUDPClient Maven / Gradle / Ivy
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/*
* 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;
/***
* 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 less of data. 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.
*
* 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(new byte[0], 0);
}
/***
* 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(InetAddress host, int port) throws IOException
{
__sendPacket.setAddress(host);
__sendPacket.setPort(port);
_socket_.send(__sendPacket);
}
/*** Same as send(host, CharGenUDPClient.DEFAULT_PORT);
* @param host the destination host
* @throws IOException on error
***/
public void send(InetAddress host) throws IOException
{
send(host, DEFAULT_PORT);
}
/***
* Receive the reply data from the server. This will always be 512 bytes
* or less. 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
{
int length;
byte[] result;
_socket_.receive(__receivePacket);
result = new byte[length = __receivePacket.getLength()];
System.arraycopy(__receiveData, 0, result, 0, length);
return result;
}
}