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

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:

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:

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:

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:

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:

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:

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:

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:

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:

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:

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:

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

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:

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:

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 must be lesser or equal to the offset plus the length of the packet's 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:

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