[Chapter 15] DatagramPacket

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| 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` |  |

## See Also

`DatagramSocket`, `InetAddress`

ContentHandlerFactory |  | DatagramSocket