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java.net

Class DatagramPacket

public final class DatagramPacket
extends Object
This class models a packet of data that is to be sent across the network using a connectionless protocol such as UDP. It contains the data to be send, as well as the destination address and port. Note that datagram packets can arrive in any order and are not guaranteed to be delivered at all.

This class can also be used for receiving data from the network.

Note that for all method below where the buffer length passed by the caller cannot exceed the actually length of the byte array passed as the buffer, if this condition is not true, then the method silently reduces the length value to maximum allowable value. Written using on-line Java Platform 1.2 API Specification, as well as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998). Status: Believed complete and correct.

Constructor Summary

DatagramPacket(byte[] buf, int length)
Initializes a new instance of DatagramPacket for receiving packets from the network.
DatagramPacket(byte[] buf, int offset, int length)
This method initializes a new instance of DatagramPacket which has the specified buffer, offset, and length.
DatagramPacket(byte[] buf, int offset, int length, InetAddress address, int port)
Initializes a new instance of DatagramPacket for transmitting packets across the network.
DatagramPacket(byte[] buf, int offset, int length, SocketAddress address)
Initializes a new instance of DatagramPacket for transmitting packets across the network.
DatagramPacket(byte[] buf, int length, InetAddress address, int port)
Initializes a new instance of DatagramPacket for transmitting packets across the network.
DatagramPacket(byte[] buf, int length, SocketAddress address)
Initializes a new instance of DatagramPacket for transmitting packets across the network.

Method Summary

InetAddress
getAddress()
Returns the address that this packet is being sent to or, if it was used to receive a packet, the address that is was received from.
byte[]
getData()
Returns the data buffer for this packet
int
getLength()
Returns the length of the data in the buffer
int
getOffset()
This method returns the current offset value into the data buffer where data will be sent from.
int
getPort()
Returns the port number this packet is being sent to or, if it was used to receive a packet, the port that it was received from.
SocketAddress
getSocketAddress()
Gets the socket address of the host this packet will be sent to/is coming from
void
setAddress(InetAddress address)
This sets the address to which the data packet will be transmitted.
void
setData(byte[] buf)
Sets the data buffer for this packet.
void
setData(byte[] buf, int offset, int length)
This method sets the data buffer for the packet.
void
setLength(int length)
Sets the length of the data in the buffer.
void
setPort(int port)
This sets the port to which the data packet will be transmitted.
void
setSocketAddress(SocketAddress address)
Sets the address of the remote host this package will be sent

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

DatagramPacket

public DatagramPacket(byte[] buf,
                      int length)
Initializes a new instance of DatagramPacket for receiving packets from the network.
Parameters:
buf - A buffer for storing the returned packet data
length - The length of the buffer (must be <= buf.length)

DatagramPacket

public DatagramPacket(byte[] buf,
                      int offset,
                      int length)
This method initializes a new instance of DatagramPacket which has the specified buffer, offset, and length.
Parameters:
buf - The buffer for holding the incoming datagram.
offset - The offset into the buffer to start writing.
length - The maximum number of bytes to read.
Since:
1.2

DatagramPacket

public DatagramPacket(byte[] buf,
                      int offset,
                      int length,
                      InetAddress address,
                      int port)
Initializes a new instance of DatagramPacket for transmitting packets across the network.
Parameters:
buf - A buffer containing the data to send
offset - The offset into the buffer to start writing from.
length - The length of the buffer (must be <= buf.length)
address - The address to send to
port - The port to send to
Since:
1.2

DatagramPacket

public DatagramPacket(byte[] buf,
                      int offset,
                      int length,
                      SocketAddress address)
            throws SocketException
Initializes a new instance of DatagramPacket for transmitting packets across the network.
Parameters:
buf - A buffer containing the data to send
offset - The offset into the buffer to start writing from.
length - The length of the buffer (must be <= buf.length)
address - The socket address to send to
Throws:
SocketException - If an error occurs
IllegalArgumentException - If address type is not supported
Since:
1.4

DatagramPacket

public DatagramPacket(byte[] buf,
                      int length,
                      InetAddress address,
                      int port)
Initializes a new instance of DatagramPacket for transmitting packets across the network.
Parameters:
buf - A buffer containing the data to send
length - The length of the buffer (must be <= buf.length)
address - The address to send to
port - The port to send to

DatagramPacket

public DatagramPacket(byte[] buf,
                      int length,
                      SocketAddress address)
            throws SocketException
Initializes a new instance of DatagramPacket for transmitting packets across the network.
Parameters:
buf - A buffer containing the data to send
length - The length of the buffer (must be <= buf.length)
address - The socket address to send to
Throws:
SocketException - If an error occurs
IllegalArgumentException - If address type is not supported
Since:
1.4

Method Details

getAddress

public InetAddress getAddress()
Returns the address that this packet is being sent to or, if it was used to receive a packet, the address that is was received from. If the constructor that doesn not take an address was used to create this object and no packet was actually read into this object, then this method returns null.
Returns:
The address for this packet.

getData

public byte[] getData()
Returns the data buffer for this packet
Returns:
This packet's data buffer

getLength

public int getLength()
Returns the length of the data in the buffer
Returns:
The length of the data

getOffset

public int getOffset()
This method returns the current offset value into the data buffer where data will be sent from.
Returns:
The buffer offset.
Since:
1.2

getPort

public int getPort()
Returns the port number this packet is being sent to or, if it was used to receive a packet, the port that it was received from. If the constructor that doesn not take an address was used to create this object and no packet was actually read into this object, then this method will return 0.
Returns:
The port number for this packet

getSocketAddress

public SocketAddress getSocketAddress()
Gets the socket address of the host this packet will be sent to/is coming from
Returns:
The socket address of the remote host
Since:
1.4

setAddress

public void setAddress(InetAddress address)
This sets the address to which the data packet will be transmitted.
Parameters:
address - The destination address
Since:
1.1

setData

public void setData(byte[] buf)
Sets the data buffer for this packet.
Parameters:
buf - The new buffer for this packet
Throws:
NullPointerException - If the argument is null
Since:
1.1

setData

public void setData(byte[] buf,
                    int offset,
                    int length)
This method sets the data buffer for the packet.
Parameters:
buf - The byte array containing the data for this packet.
offset - The offset into the buffer to start reading data from.
length - The number of bytes of data in the buffer.
Throws:
NullPointerException - If the argument is null
Since:
1.2

setLength

public void setLength(int length)
Sets the length of the data in the buffer.
Parameters:
length - The new length. (Where len <= buf.length)
Throws:
IllegalArgumentException - If the length is negative or if the length is greater than the packet's data buffer length
Since:
1.1

setPort

public void setPort(int port)
This sets the port to which the data packet will be transmitted.
Parameters:
port - The destination port
Since:
1.1

setSocketAddress

public void setSocketAddress(SocketAddress address)
            throws IllegalArgumentException
Sets the address of the remote host this package will be sent
Parameters:
address - The socket address of the remove host
Throws:
IllegalArgumentException - If address type is not supported
Since:
1.4
DatagramPacket.java -- Class to model a packet to be sent via UDP Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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