panda.net.tftp.TFTPAckPacket Maven / Gradle / Ivy
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package panda.net.tftp;
import java.net.DatagramPacket;
import java.net.InetAddress;
/***
* A final class derived from TFTPPacket definiing the TFTP Acknowledgement packet type.
*
* 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 panda.net.tftp.TFTPClient} class
* {@link panda.net.tftp.TFTPClient#receiveFile receiveFile()} and
* {@link panda.net.tftp.TFTPClient#sendFile sendFile()} methods.
*
* @see TFTPPacket
* @see TFTPPacketException
* @see TFTP
***/
public final class TFTPAckPacket extends TFTPPacket {
/*** The block number being acknowledged by the packet. ***/
int _blockNumber;
/***
* Creates an acknowledgment packet to be sent to a host at a given port acknowledging receipt
* of a block.
*
* @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 blockNumber The block number being acknowledged.
***/
public TFTPAckPacket(InetAddress destination, int port, int blockNumber) {
super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
_blockNumber = blockNumber;
}
/***
* Creates an acknowledgement packet based from a received datagram. Assumes the datagram is at
* least length 4, else an ArrayIndexOutOfBoundsException may be thrown.
*
* @param datagram The datagram containing the received acknowledgement.
* @throws TFTPPacketException If the datagram isn't a valid TFTP acknowledgement packet.
***/
TFTPAckPacket(DatagramPacket datagram) throws TFTPPacketException {
super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(), datagram.getPort());
byte[] data;
data = datagram.getData();
if (getType() != data[1]) {
throw new TFTPPacketException("TFTP operator code does not match type.");
}
_blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
}
/***
* 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.
*
* @param datagram The datagram to create.
* @param data The buffer to store the packet and to use in the datagram.
* @return The datagram argument.
***/
@Override
DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data) {
data[0] = 0;
data[1] = (byte)_type;
data[2] = (byte)((_blockNumber & 0xffff) >> 8);
data[3] = (byte)(_blockNumber & 0xff);
datagram.setAddress(_address);
datagram.setPort(_port);
datagram.setData(data);
datagram.setLength(4);
return datagram;
}
/***
* Creates a UDP datagram containing all the TFTP acknowledgement 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 panda.net.tftp.TFTPClient} class. Under normal
* circumstances, you should not have a need to call this method.
*
* @return A UDP datagram containing the TFTP acknowledgement packet.
***/
@Override
public DatagramPacket newDatagram() {
byte[] data;
data = new byte[4];
data[0] = 0;
data[1] = (byte)_type;
data[2] = (byte)((_blockNumber & 0xffff) >> 8);
data[3] = (byte)(_blockNumber & 0xff);
return new DatagramPacket(data, data.length, _address, _port);
}
/***
* Returns the block number of the acknowledgement.
*
* @return The block number of the acknowledgement.
***/
public int getBlockNumber() {
return _blockNumber;
}
/***
* Sets the block number of the acknowledgement.
*
* @param blockNumber the number to set
***/
public void setBlockNumber(int blockNumber) {
_blockNumber = blockNumber;
}
}