DatagramPacket (Java SE 21 & JDK 21)
Description: declaration: module: java.base, package: java.net, class: DatagramPacket
Keywords: java.net.DatagramPacket class

Module java.base
Package java.net

# Class DatagramPacket

java.lang.Object
java.net.DatagramPacket

public final class DatagramPacket extends Object
This class represents a datagram packet.

Datagram packets are used to implement a connectionless packet delivery service. Each message is routed from one machine to another based solely on information contained within that packet. Multiple packets sent from one machine to another might be routed differently, and might arrive in any order. Packet delivery is not guaranteed.

Unless otherwise specified, passing a `null` argument causes a `NullPointerException` to be thrown.

Methods and constructors of `DatagramPacket` accept parameters of type `SocketAddress`. `DatagramPacket` supports `InetSocketAddress`, and may support additional `SocketAddress` sub-types.

Since:
  1.0

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `DatagramPacket(byte[] buf, int length)`
  Constructs a `DatagramPacket` for receiving packets of length `length`.
  `DatagramPacket(byte[] buf, int offset, int length)`
  Constructs a `DatagramPacket` for receiving packets of length `length`, specifying an offset into the buffer.
  `DatagramPacket(byte[] buf, int offset, int length, InetAddress address, int port)`
  Constructs a datagram packet for sending packets of length `length` with offset `offset` to the specified port number on the specified host.
  `DatagramPacket(byte[] buf, int offset, int length, SocketAddress address)`
  Constructs a datagram packet for sending packets of length `length` with offset `offset` to the specified port number on the specified host.
  `DatagramPacket(byte[] buf, int length, InetAddress address, int port)`
  Constructs a datagram packet for sending packets of length `length` to the specified port number on the specified host.
  `DatagramPacket(byte[] buf, int length, SocketAddress address)`
  Constructs a datagram packet for sending packets of length `length` to the specified port number on the specified host.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `InetAddress`
  `getAddress()`
  Returns the IP address of the machine to which this datagram is being sent or from which the datagram was received, or `null` if not set.
  `byte[]`
  `getData()`
  Returns the data buffer.
  `int`
  `getLength()`
  Returns the length of the data to be sent or the length of the data received.
  `int`
  `getOffset()`
  Returns the offset of the data to be sent or the offset of the data received.
  `int`
  `getPort()`
  Returns the port number on the remote host to which this datagram is being sent or from which the datagram was received, or 0 if not set.
  `SocketAddress`
  `getSocketAddress()`
  Returns the `SocketAddress` (usually IP address + port number) of the remote host that this packet is being sent to or is coming from.
  `void`
  `setAddress(InetAddress iaddr)`
  Sets the IP address of the machine to which this datagram is being sent.
  `void`
  `setData(byte[] buf)`
  Set the data buffer for this packet.
  `void`
  `setData(byte[] buf, int offset, int length)`
  Set the data buffer for this packet.
  `void`
  `setLength(int length)`
  Set the length for this packet.
  `void`
  `setPort(int iport)`
  Sets the port number on the remote host to which this datagram is being sent.
  `void`
  `setSocketAddress(SocketAddress address)`
  Sets the SocketAddress (usually IP address + port number) of the remote host to which this datagram is being sent.

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int offset, int length)
    Constructs a `DatagramPacket` for receiving packets of length `length`, specifying an offset into the buffer.

    The `length` argument must be less than or equal to `buf.length`.

    Parameters:
      `buf` - buffer for holding the incoming datagram.
      `offset` - the offset for the buffer
      `length` - the number of bytes to read.
    Throws:
      `IllegalArgumentException` - if the length or offset is negative, or if the length plus the offset is greater than the length of the packet's given buffer.
    Since:
      1.2

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int length)
    Constructs a `DatagramPacket` for receiving packets of length `length`.

    The `length` argument must be less than or equal to `buf.length`.

    Parameters:
      `buf` - buffer for holding the incoming datagram.
      `length` - the number of bytes to read.
    Throws:
      `IllegalArgumentException` - if the length is negative or if the length is greater than the length of the packet's given buffer.

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int offset, int length, InetAddress address, int port)
    Constructs a datagram packet for sending packets of length `length` with offset `offset` to the specified port number on the specified host. The `length` argument must be less than or equal to `buf.length`.
    Parameters:
      `buf` - the packet data.
      `offset` - the packet data offset.
      `length` - the packet data length.
      `address` - the destination address, or `null`.
      `port` - the destination port number.
    Throws:
      `IllegalArgumentException` - if the length or offset is negative, or if the length plus the offset is greater than the length of the packet's given buffer, or if the port is out of range.
    Since:
      1.2
    See Also:
      - `InetAddress`

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int offset, int length, SocketAddress address)
    Constructs a datagram packet for sending packets of length `length` with offset `offset` to the specified port number on the specified host. The `length` argument must be less than or equal to `buf.length`.
    Parameters:
      `buf` - the packet data.
      `offset` - the packet data offset.
      `length` - the packet data length.
      `address` - the destination socket address.
    Throws:
      `IllegalArgumentException` - if address is null or its type is not supported, or if the length or offset is negative, or if the length plus the offset is greater than the length of the packet's given buffer.
    Since:
      1.4
    See Also:
      - `InetAddress`

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int length, InetAddress address, int port)
    Constructs a datagram packet for sending packets of length `length` to the specified port number on the specified host. The `length` argument must be less than or equal to `buf.length`.
    Parameters:
      `buf` - the packet data.
      `length` - the packet length.
      `address` - the destination address, or `null`.
      `port` - the destination port number.
    Throws:
      `IllegalArgumentException` - if the length is negative, or if the length is greater than the length of the packet's given buffer, or if the port is out of range.
    See Also:
      - `InetAddress`

  - ### DatagramPacket

    public DatagramPacket(byte[] buf, int length, SocketAddress address)
    Constructs a datagram packet for sending packets of length `length` to the specified port number on the specified host. The `length` argument must be less than or equal to `buf.length`.
    Parameters:
      `buf` - the packet data.
      `length` - the packet length.
      `address` - the destination address.
    Throws:
      `IllegalArgumentException` - if address is null or its type is not supported, or if the length is negative, or if the length is greater than the length of the packet's given buffer, or if the port is out of range.
    Since:
      1.4
    See Also:
      - `InetAddress`

- ## Method Details

  - ### getAddress

    public InetAddress getAddress()
    Returns the IP address of the machine to which this datagram is being sent or from which the datagram was received, or `null` if not set.
    Returns:
      the IP address of the machine to which this datagram is being sent or from which the datagram was received.
    See Also:
      - `InetAddress`
      - `setAddress(java.net.InetAddress)`

  - ### getPort

    public int getPort()
    Returns the port number on the remote host to which this datagram is being sent or from which the datagram was received, or 0 if not set.
    Returns:
      the port number on the remote host to which this datagram is being sent or from which the datagram was received.
    See Also:
      - `setPort(int)`

  - ### getData

    public byte[] getData()
    Returns the data buffer. The data received or the data to be sent starts from the `offset` in the buffer, and runs for `length` long.
    Returns:
      the buffer used to receive or send data
    See Also:
      - `setData(byte[], int, int)`

  - ### getOffset

    public int getOffset()
    Returns the offset of the data to be sent or the offset of the data received.
    Returns:
      the offset of the data to be sent or the offset of the data received.
    Since:
      1.2

  - ### getLength

    public int getLength()
    Returns the length of the data to be sent or the length of the data received.
    Returns:
      the length of the data to be sent or the length of the data received.
    See Also:
      - `setLength(int)`

  - ### setData

    public void setData(byte[] buf, int offset, int length)
    Set the data buffer for this packet. This sets the data, length and offset of the packet.
    Parameters:
      `buf` - the buffer to set for this packet
      `offset` - the offset into the data
      `length` - the length of the data and/or the length of the buffer used to receive data
    Throws:
      `IllegalArgumentException` - if the length or offset is negative, or if the length plus the offset is greater than the length of the packet's given buffer.
    Since:
      1.2
    See Also:
      - `getData()`
      - `getOffset()`
      - `getLength()`

  - ### setAddress

    public void setAddress(InetAddress iaddr)
    Sets the IP address of the machine to which this datagram is being sent.
    Parameters:
      `iaddr` - the `InetAddress`, or `null`.
    Since:
      1.1
    See Also:
      - `getAddress()`

  - ### setPort

    public void setPort(int iport)
    Sets the port number on the remote host to which this datagram is being sent.
    Parameters:
      `iport` - the port number
    Throws:
      `IllegalArgumentException` - if the port is out of range
    Since:
      1.1
    See Also:
      - `getPort()`

  - ### setSocketAddress

    public void setSocketAddress(SocketAddress address)
    Sets the SocketAddress (usually IP address + port number) of the remote host to which this datagram is being sent.
    Parameters:
      `address` - the `SocketAddress`
    Throws:
      `IllegalArgumentException` - if address is null or is a SocketAddress subclass not supported.
    Since:
      1.4
    See Also:
      - `getSocketAddress()`

  - ### getSocketAddress

    public SocketAddress getSocketAddress()
    Returns the `SocketAddress` (usually IP address + port number) of the remote host that this packet is being sent to or is coming from.
    Returns:
      the `SocketAddress`
    Since:
      1.4
    See Also:
      - `setSocketAddress(java.net.SocketAddress)`

  - ### setData

    public void setData(byte[] buf)
    Set the data buffer for this packet. With the offset of this DatagramPacket set to 0, and the length set to the length of `buf`.
    Parameters:
      `buf` - the buffer to set for this packet.
    Since:
      1.1
    See Also:
      - `getLength()`
      - `getData()`

  - ### setLength

    public void setLength(int length)
    Set the length for this packet. The length of the packet is the number of bytes from the packet's data buffer that will be sent, or the number of bytes of the packet's data buffer that will be used for receiving data. The `length` plus the `offset` must be lesser or equal to the length of the packet's data buffer.
    Parameters:
      `length` - the length to set for this packet.
    Throws:
      `IllegalArgumentException` - if the length is negative, or if the length plus the offset is greater than the length of the packet's data buffer.
    Since:
      1.1
    See Also:
      - `getLength()`
      - `setData(byte[], int, int)`