org.apache.commons.net.tftp
Class TFTPPacket

java.lang.Object
  extended byorg.apache.commons.net.tftp.TFTPPacket
Direct Known Subclasses:
TFTPAckPacket, TFTPDataPacket, TFTPErrorPacket, TFTPRequestPacket

public abstract class TFTPPacket
extends Object

TFTPPacket is an abstract class encapsulating the functionality common to the 5 types of TFTP packets. It also provides a static factory method that will create the correct TFTP packet instance from a datagram. This relieves the programmer from having to figure out what kind of TFTP packet is contained in a datagram and create it himself.

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 TFTPClient class receiveFile() and sendFile() methods.

Author:
Daniel F. Savarese
See Also:
TFTPPacketException, TFTP

Field Summary
(package private)  InetAddress _address
          The host the packet is going to be sent or where it came from.
(package private)  int _port
          The port the packet came from or is going to.
(package private)  int _type
          The type of packet.
static int ACKNOWLEDGEMENT
          This is the actual TFTP spec identifier and is equal to 4.
static int DATA
          This is the actual TFTP spec identifier and is equal to 3.
static int ERROR
          This is the actual TFTP spec identifier and is equal to 5.
(package private) static int MIN_PACKET_SIZE
          The minimum size of a packet.
static int READ_REQUEST
          This is the actual TFTP spec identifier and is equal to 1.
static int SEGMENT_SIZE
          The TFTP data packet maximum segment size in bytes.
static int WRITE_REQUEST
          This is the actual TFTP spec identifier and is equal to 2.
 
Constructor Summary
(package private) TFTPPacket(int type, InetAddress address, int port)
          This constructor is not visible outside of the package.
 
Method Summary
(package private) abstract  DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
          This is an abstract method only available within the package for implementing efficient datagram transport by elminating buffering.
 InetAddress getAddress()
          Returns the address of the host where the packet is going to be sent or where it came from.
 int getPort()
          Returns the port where the packet is going to be sent or where it came from.
 int getType()
          Returns the type of the packet.
abstract  DatagramPacket newDatagram()
          Creates a UDP datagram containing all the TFTP packet data in the proper format.
static TFTPPacket newTFTPPacket(DatagramPacket datagram)
          When you receive a datagram that you expect to be a TFTP packet, you use this factory method to create the proper TFTPPacket object encapsulating the data contained in that datagram.
 void setAddress(InetAddress address)
          Sets the host address where the packet is going to be sent.
 void setPort(int port)
          Sets the port where the packet is going to be sent.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

MIN_PACKET_SIZE

static final int MIN_PACKET_SIZE
The minimum size of a packet. This is 4 bytes. It is enough to store the opcode and blocknumber or other required data depending on the packet type.

See Also:
Constant Field Values

READ_REQUEST

public static final int READ_REQUEST
This is the actual TFTP spec identifier and is equal to 1. Identifier returned by getType() indicating a read request packet.

See Also:
Constant Field Values

WRITE_REQUEST

public static final int WRITE_REQUEST
This is the actual TFTP spec identifier and is equal to 2. Identifier returned by getType() indicating a write request packet.

See Also:
Constant Field Values

DATA

public static final int DATA
This is the actual TFTP spec identifier and is equal to 3. Identifier returned by getType() indicating a data packet.

See Also:
Constant Field Values

ACKNOWLEDGEMENT

public static final int ACKNOWLEDGEMENT
This is the actual TFTP spec identifier and is equal to 4. Identifier returned by getType() indicating an acknowledgement packet.

See Also:
Constant Field Values

ERROR

public static final int ERROR
This is the actual TFTP spec identifier and is equal to 5. Identifier returned by getType() indicating an error packet.

See Also:
Constant Field Values

SEGMENT_SIZE

public static final int SEGMENT_SIZE
The TFTP data packet maximum segment size in bytes. This is 512 and is useful for those familiar with the TFTP protocol who want to use the TFTP class methods to implement their own TFTP servers or clients.

See Also:
Constant Field Values

_type

int _type
The type of packet.


_port

int _port
The port the packet came from or is going to.


_address

InetAddress _address
The host the packet is going to be sent or where it came from.

Constructor Detail

TFTPPacket

TFTPPacket(int type,
           InetAddress address,
           int port)
This constructor is not visible outside of the package. It is used by subclasses within the package to initialize base data.

Parameters:
type - The type of the packet.
address - The host the packet came from or is going to be sent.
port - The port the packet came from or is going to be sent.
Method Detail

newTFTPPacket

public static final TFTPPacket newTFTPPacket(DatagramPacket datagram)
                                      throws TFTPPacketException
When you receive a datagram that you expect to be a TFTP packet, you use this factory method to create the proper TFTPPacket object encapsulating the data contained in that datagram. This method is the only way you can instantiate a TFTPPacket derived class from a datagram.

Parameters:
datagram - The datagram containing a TFTP packet.
Returns:
The TFTPPacket object corresponding to the datagram.
Throws:
TFTPPacketException - If the datagram does not contain a valid TFTP packet.

_newDatagram

abstract DatagramPacket _newDatagram(DatagramPacket datagram,
                                     byte[] data)
This is an abstract 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 should be set as the datagram's data and the datagram returned.

Parameters:
datagram - The datagram to create.
data - The buffer to store the packet and to use in the datagram.
Returns:
The datagram argument.

newDatagram

public abstract DatagramPacket newDatagram()
Creates a UDP datagram containing all the TFTP packet data in the proper format. This is an abstract method, exposed to the programmer in case he wants to implement his own TFTP client instead of using the TFTPClient class. Under normal circumstances, you should not have a need to call this method.

Returns:
A UDP datagram containing the TFTP packet.

getType

public final int getType()
Returns the type of the packet.

Returns:
The type of the packet.

getAddress

public final InetAddress getAddress()
Returns the address of the host where the packet is going to be sent or where it came from.

Returns:
The type of the packet.

getPort

public final int getPort()
Returns the port where the packet is going to be sent or where it came from.

Returns:
The port where the packet came from or where it is going.

setPort

public final void setPort(int port)
Sets the port where the packet is going to be sent.


setAddress

public final void setAddress(InetAddress address)
Sets the host address where the packet is going to be sent.