Chapter 15
The java.net Package

DatagramPacket

Name

DatagramPacket

Synopsis

Class Name:

java.net.DatagramPacket

Superclass:

java.lang.Object

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

JDK 1.0 or later

Description

The DatagramPacket class represents a packet of data that can be sent and received over the network using a DatagramSocket. The class is used to implement connectionless data communication.

Class Summary

public final class java.net.DatagramPacket extends java.lang.Object {
  // Constructors
  public DatagramPacket(byte[] ibuf, int ilength);
  public DatagramPacket(byte[] ibuf, int ilength, 
                        InetAddress iaddr, int iport);
  // Instance Methods
  public synchronized InetAddress getAddress();
  public synchronized byte[] getData();
  public synchronized int getLength();
  public synchronized int getPort();
  public synchronized void setAddress(InetAddress iaddr);   // New in 1.1
  public synchronized void setData(byte[] ibuf);            // New in 1.1
  public synchronized void setLength(int ilength);          // New in 1.1
  public synchronized void setPort(int iport);              // New in 1.1
}

Constructors

DatagramPacket

public DatagramPacket(byte ibuf[], int ilength)

Parameters

ibuf

The data buffer for receiving incoming bytes.

ilength

The number of bytes to read.

Description

This constructor creates a DatagramPacket that receives data. The value of ilength must be less than or equal to ibuf.length. This DatagramPacket can be passed to DatagramSocket.receive().

 public DatagramPacket(byte ibuf[], int ilength, InetAddress iaddr, int iport)

Parameters

ibuf

The data buffer for the packet.

ilength

The number of bytes to send.

iaddr

The destination address.

iport

The destination port number.

Description

This constructor creates a DatagramPacket that sends packets of length ilength to the given port of the specified address. The value of ilength must be less than or equal to ibuf.length. The packets are sent using DatagramSocket.send().

Instance Methods

getAddress

public synchronized InetAddress getAddress()

Returns

The IP address of the packet.

Description

If this packet has been received, the method returns the address of the machine that sent it. If the packet is being sent, the method returns the destination address.

getData

public synchronized byte[] getData()

Returns

The packet data.

Description

This method returns the data buffer associated with this DatagramPacket object. This data is either the data being sent or the data that has been received.

getLength

public synchronized int getLength()

Returns

The packet length.

Description

This method returns the length of the message in the buffer associated with this DatagramPacket. This length is either the length of the data being sent or the length of the data that has been received.

getPort

public synchronized int getPort()

Returns

The port number of the packet.

Description

If this packet has been received, the method returns the port number of the machine that sent it. If the packet is being sent, the method returns the destination port number.

setAddress

public synchronized void setAddress(InetAddress iaddr)

Availability

New as of JDK 1.1

Parameters

iaddr: The destination address for the packet.

Description

This method sets the destination address for this packet. When the packet is sent using DatagramSocket.send(), it is sent to the specified address.

setData

public synchronized void setData(byte[] ibuf)

Availability

New as of JDK 1.1

Parameters

ibuf: The data buffer for the packet.

Description

This method sets the data for this packet. When the packet is sent using DatagramSocket.send(), the specified data is sent.

setLength

public synchronized void setLength(int ilength)

Availability

New as of JDK 1.1

Parameters

ilength: The number of bytes to send.

Description

This method sets the length of the data to be sent for this packet. When the packet is sent using DatagramSocket.send(), the specified amount of data is sent.

setPort

public synchronized void setPort(int iport)

Availability

New as of JDK 1.1

Parameters

iport: The port number for the packet.

Description

This method sets the destination port number for this packet. When the packet is sent using DatagramSocket.send(), it is sent to the specified port.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`equals(Object)`	`Object`
`finalize()`	`Object`	`getClass()`	`Object`
`hashCode()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`toString()`	`Object`
`wait()`	`Object`	`wait(long)`	`Object`
`wait(long, int)`	`Object`