java.net

Class DatagramPacket

java.lang.Object

java.net.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.

Author:

Warren Levy (warrenl@cygnus.com), Aarom M. Renn (arenn@urbanophile.com) (Documentation comments)

Constructor Summary

Constructors

Constructor and Description
DatagramPacket(byte[] buf, int length) Initializes a new instance of DatagramPacket for receiving packets from 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 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, SocketAddress address) Initializes a new instance of DatagramPacket for transmitting packets across the network.

Method Summary

Modifier and Type	Method and Description
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

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

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 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 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,
                      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 Detail

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