DatagramPacket setLength(int) in Java

setLength(int): This method is available in the java.net.DatagramPacket class of Java.

Syntax:

void java.net.DatagramPacket.setLength(int length)

This method takes one argument. This method sets the length for this packet. The length of the packet isthe 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.

Note: The length must be lesser or equal to the offset plus the length of the packet's buffer.

Parameters: One parameter is required for this method.

length: the length to set for this packet.

Returns: NA

Throws:

1. IllegalArgumentException - if the length is negative,or if the length plus the offset is greater than the length of the packet's data buffer.

Approach 1: When no exception

Java

package com.DatagramPacket;

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class DatagramPacketsetLength {
    public static void main(String[] args) 
                 throws UnknownHostException {

        byte buf[] = { 'a', 'b', 'c', 'd', 'e' };
        int offset = 0, length = 5;
        InetAddress address = InetAddress.getLocalHost();
        int port = 100;
        DatagramPacket datagramPacket = 
        new DatagramPacket(buf, offset, length, address, port);

        datagramPacket.setLength(length);
        System.out.println("Successfully sets the length");
    }
}

Output:

Successfully sets the length

Approach 2: IllegalArgumentException 

Java

package com.DatagramPacket;

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class DatagramPacketsetLength {
    public static void main(String[] args) 
                    throws UnknownHostException {

        byte buf[] = { 'a', 'b', 'c', 'd', 'e' };
        int offset = 0, length = 50;
        InetAddress address = InetAddress.getLocalHost();
        int port = 100;
        DatagramPacket datagramPacket = 
        new DatagramPacket(buf, offset, length, address, port);

        datagramPacket.setLength(length);
        System.out.println("Successfully sets the length");
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: illegal length or offset
	at java.base/java.net.DatagramPacket.setData(DatagramPacket.java:300)
	at java.base/java.net.DatagramPacket.<init>(DatagramPacket.java:137)
	at com.DatagramPacket.DatagramPacketsetLength.main(DatagramPacketsetLength.java:14)

Some other methods of DatagramPacket class

DatagramPacket(byte[], int): This method constructs a DatagramPacket for receiving packets of length.

DatagramPacket(byte[], int, int): This method constructs a DatagramPacket for receiving length packets, specifying an offset into the buffer.

DatagramPacket(byte[], int, SocketAddress): This method constructs a datagram packet for sending packets of length to the specified port number on the specified host

DatagramPacket(byte[], int, InetAddress, int): This method constructs a datagram packet for sending packets of length to the specified port number on the specified host.

DatagramPacket(byte[], int, int, SocketAddress): This method constructs a datagram packet for sending packets of length with offset to the specified port number on the specified host.

DatagramPacket(byte[], int, int, InetAddress, int): This method constructs a datagram packet for sending length packets with offset to the specified port number on the specified host.

getAddress(): This method 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.

getData(): This method returns the data buffer.

getLength(): This method returns the length of the data to be sent or the length of the data received.

getOffset(): This method returns the offset of the data to be sent or the offset of the data received.

getPort(): This method 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.

getSocketAddress(): This method returns the SocketAddress (usually IP address + port number) of the remote host that this packet is being sent to or is coming from.

setAddress(InetAddress): This method sets the IP address of the machine to which this datagram is being sent.

setData(byte[]): This method sets the data buffer for this packet. With the offset of this DatagramPacket set to 0, and the length set to the length of buf.

setData(byte[], int, int): This method sets the data buffer for this packet. This sets the data, length, and offset of the packet.

setLength(int): This method sets 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.

setPort(int): This method sets the port number on the remote host to which this datagram is being sent.

setSocketAddress(SocketAddress): This method sets the SocketAddress (usually IP address + port number) of the remote host to which this datagram is being sent.