panda.net.chargen.CharGenUDPClient Maven / Gradle / Ivy
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package panda.net.chargen;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import panda.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 panda.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 panda.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.
* @exception 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.
* @exception 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;
}
}