org.apache.commons.net
Class CharGenUDPClient

java.lang.Object
  org.apache.commons.net.DatagramSocketClient
      org.apache.commons.net.CharGenUDPClient

public final class CharGenUDPClient
extends 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 open and call send to send the datagram that will initiate the data reply. For chargen or quote of the day, just call 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 close() to clean up properly.

Author:

Daniel F. Savarese

See Also:

CharGenTCPClient

Field Summary

static int	CHARGEN_PORT The character generator port value of 19 according to RFC 864.
static int	DEFAULT_PORT The default chargen port.
static int	NETSTAT_PORT The netstat port value of 19.
static int	QUOTE_OF_DAY_PORT The quote of the day port value of 17 according to RFC 865.
static int	SYSTAT_PORT The systat port value of 11 according to RFC 866.

Fields inherited from class org.apache.commons.net.DatagramSocketClient

_isOpen_, _socket_, _socketFactory_, _timeout_

Constructor Summary

CharGenUDPClient()
The default CharGenUDPClient constructor.

Method Summary

byte[]	receive() Receive the reply data from the server.
void	send(InetAddress host) Same as send(host, CharGenUDPClient.DEFAULT_PORT);
void	send(InetAddress host, int port) Sends the data initiation datagram.

Methods inherited from class org.apache.commons.net.DatagramSocketClient

close, getDefaultTimeout, getLocalAddress, getLocalPort, getSoTimeout, isOpen, open, open, open, setDatagramSocketFactory, setDefaultTimeout, setSoTimeout

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SYSTAT_PORT

public static final int SYSTAT_PORT

The systat port value of 11 according to RFC 866.

See Also:

Constant Field Values

NETSTAT_PORT

public static final int NETSTAT_PORT

The netstat port value of 19.

See Also:

Constant Field Values

QUOTE_OF_DAY_PORT

public static final int QUOTE_OF_DAY_PORT

The quote of the day port value of 17 according to RFC 865.

See Also:

Constant Field Values

CHARGEN_PORT

public static final int CHARGEN_PORT

The character generator port value of 19 according to RFC 864.

See Also:

Constant Field Values

DEFAULT_PORT

public static final int DEFAULT_PORT

The default chargen port. It is set to 19 according to RFC 864.

See Also:

Constant Field Values

Constructor Detail

CharGenUDPClient

public CharGenUDPClient()

The default CharGenUDPClient constructor. It initializes some internal data structures for sending and receiving the necessary datagrams for the chargen and related protocols.

Method Detail

send

public void send(InetAddress host,
                 int port)
          throws IOException

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.

Parameters:

host - The address of the server.

port - The port of the service.

Throws:

IOException - If an error occurs while sending the datagram.

send

public void send(InetAddress host)
          throws IOException

Same as send(host, CharGenUDPClient.DEFAULT_PORT);

Throws:

IOException

receive

public byte[] receive()
               throws IOException

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.

Returns:

The reply data from the server.

Throws:

IOException - If an error occurs while receiving the datagram.