org.apache.commons.net

Class 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_, _socketFactory_, _socket_, _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

Field Details

CHARGEN_PORT

public static final int CHARGEN_PORT
The character generator port value of 19 according to RFC 864. **
Field Value:
19

DEFAULT_PORT

public static final int DEFAULT_PORT
The default chargen port. It is set to 19 according to RFC 864. **
Field Value:
19

NETSTAT_PORT

public static final int NETSTAT_PORT
The netstat port value of 19. **
Field Value:
15

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. **
Field Value:
17

SYSTAT_PORT

public static final int SYSTAT_PORT
The systat port value of 11 according to RFC 866. **
Field Value:
11

Constructor Details

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 Details

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.

send

public void send(InetAddress host)
            throws IOException
Same as send(host, CharGenUDPClient.DEFAULT_PORT); **

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.