Java tutorial
/* * Copyright 2001-2005 The Apache Software Foundation * * Licensed 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.eredlab.g4.ccl.net.tftp; import java.net.DatagramPacket; import java.net.InetAddress; /*** * A final class derived from TFTPPacket definiing the TFTP Error * packet type. * <p> * Details regarding the TFTP protocol and the format of TFTP packets can * be found in RFC 783. But the point of these classes is to keep you * from having to worry about the internals. Additionally, only very * few people should have to care about any of the TFTPPacket classes * or derived classes. Almost all users should only be concerned with the * {@link org.apache.commons.net.tftp.TFTPClient} class * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()} * and * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()} * methods. * <p> * <p> * @author Daniel F. Savarese * @see TFTPPacket * @see TFTPPacketException * @see TFTP ***/ public final class TFTPErrorPacket extends TFTPPacket { /*** The undefined error code according to RFC 783, value 0. ***/ public static final int UNDEFINED = 0; /*** The file not found error code according to RFC 783, value 1. ***/ public static final int FILE_NOT_FOUND = 1; /*** The access violation error code according to RFC 783, value 2. ***/ public static final int ACCESS_VIOLATION = 2; /*** The disk full error code according to RFC 783, value 3. ***/ public static final int OUT_OF_SPACE = 3; /*** * The illegal TFTP operation error code according to RFC 783, value 4. ***/ public static final int ILLEGAL_OPERATION = 4; /*** The unknown transfer id error code according to RFC 783, value 5. ***/ public static final int UNKNOWN_TID = 5; /*** The file already exists error code according to RFC 783, value 6. ***/ public static final int FILE_EXISTS = 6; /*** The no such user error code according to RFC 783, value 7. ***/ public static final int NO_SUCH_USER = 7; /*** The error code of this packet. ***/ int _error; /*** The error message of this packet. ***/ String _message; /*** * Creates an error packet to be sent to a host at a given port * with an error code and error message. * <p> * @param destination The host to which the packet is going to be sent. * @param port The port to which the packet is going to be sent. * @param error The error code of the packet. * @param message The error message of the packet. ***/ public TFTPErrorPacket(InetAddress destination, int port, int error, String message) { super(TFTPPacket.ERROR, destination, port); _error = error; _message = message; } /*** * Creates an error packet based from a received * datagram. Assumes the datagram is at least length 4, else an * ArrayIndexOutOfBoundsException may be thrown. * <p> * @param datagram The datagram containing the received error. * @throws TFTPPacketException If the datagram isn't a valid TFTP * error packet. ***/ TFTPErrorPacket(DatagramPacket datagram) throws TFTPPacketException { super(TFTPPacket.ERROR, datagram.getAddress(), datagram.getPort()); int index, length; byte[] data; StringBuffer buffer; data = datagram.getData(); length = datagram.getLength(); if (getType() != data[1]) throw new TFTPPacketException("TFTP operator code does not match type."); _error = (((data[2] & 0xff) << 8) | (data[3] & 0xff)); if (length < 5) throw new TFTPPacketException("Bad error packet. No message."); index = 4; buffer = new StringBuffer(); while (index < length && data[index] != 0) { buffer.append((char) data[index]); ++index; } _message = buffer.toString(); } /*** * This is a method only available within the package for * implementing efficient datagram transport by elminating buffering. * It takes a datagram as an argument, and a byte buffer in which * to store the raw datagram data. Inside the method, the data * is set as the datagram's data and the datagram returned. * <p> * @param datagram The datagram to create. * @param data The buffer to store the packet and to use in the datagram. * @return The datagram argument. ***/ DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data) { int length; length = _message.length(); data[0] = 0; data[1] = (byte) _type; data[2] = (byte) ((_error & 0xffff) >> 8); data[3] = (byte) (_error & 0xff); System.arraycopy(_message.getBytes(), 0, data, 4, length); data[length + 4] = 0; datagram.setAddress(_address); datagram.setPort(_port); datagram.setData(data); datagram.setLength(length + 4); return datagram; } /*** * Creates a UDP datagram containing all the TFTP * error packet data in the proper format. * This is a method exposed to the programmer in case he * wants to implement his own TFTP client instead of using * the {@link org.apache.commons.net.tftp.TFTPClient} * class. * Under normal circumstances, you should not have a need to call this * method. * <p> * @return A UDP datagram containing the TFTP error packet. ***/ public DatagramPacket newDatagram() { byte[] data; int length; length = _message.length(); data = new byte[length + 5]; data[0] = 0; data[1] = (byte) _type; data[2] = (byte) ((_error & 0xffff) >> 8); data[3] = (byte) (_error & 0xff); System.arraycopy(_message.getBytes(), 0, data, 4, length); data[length + 4] = 0; return new DatagramPacket(data, data.length, _address, _port); } /*** * Returns the error code of the packet. * <p> * @return The error code of the packet. ***/ public int getError() { return _error; } /*** * Returns the error message of the packet. * <p> * @return The error message of the packet. ***/ public String getMessage() { return _message; } }