Package org.apache.commons.net.chargen

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.

    See Also:
    CharGenTCPClient

    • 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​(java.net.InetAddress host,
                 int port)
          throws java.io.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:
        java.io.IOException - If an error occurs while sending the datagram.

      • send

        public void send​(java.net.InetAddress host)
          throws java.io.IOException
        Same as send(host, CharGenUDPClient.DEFAULT_PORT);
        Parameters:
        host - the destination host
        Throws:
        java.io.IOException - on error

      • receive

        public byte[] receive()
               throws java.io.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:
        java.io.IOException - If an error occurs while receiving the datagram.