Java DatagramSocket and DatagramPacket

Java DatagramSocket and DatagramPacket classes are used for connection-less socket programming.

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Java DatagramSocket class

Java DatagramSocket class represents a connection-less socket for sending and receiving datagram packets.

A datagram is basically an information but there is no guarantee of its content, arrival or arrival time.

Commonly used Constructors of DatagramSocket class

• DatagramSocket() throws SocketEeption: it creates a datagram socket and binds it with the available Port Number on the localhost machine.
• DatagramSocket(int port) throws SocketEeption: it creates a datagram socket and binds it with the given Port Number.
• DatagramSocket(int port, InetAddress address) throws SocketEeption: it creates a datagram socket and binds it with the specified port number and host address.

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Java DatagramPacket class

Java DatagramPacket is a message that can be sent or received. If you send multiple packet, it may arrive in any order. Additionally, packet delivery is not guaranteed.

Commonly used Constructors of DatagramPacket class

• DatagramPacket(byte[] barr, int length): it creates a datagram packet. This constructor is used to receive the packets.
• DatagramPacket(byte[] barr, int length, InetAddress address, int port): it creates a datagram packet. This constructor is used to send the packets.

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Example of Sending DatagramPacket by DatagramSocket

1. //DSender.java  
2. import java.net.*;  
3. public class DSender{  
4.   public static void main(String[] args) throws Exception {  
5.     DatagramSocket ds = new DatagramSocket();  
6.     String str = "Welcome java";  
7.     InetAddress ip = InetAddress.getByName("127.0.0.1");  
8.      
9.     DatagramPacket dp = new DatagramPacket(str.getBytes(), str.length(), ip, 3000);  
10.     ds.send(dp);  
11.     ds.close();  
12.   }  
13. }  

Example of Receiving DatagramPacket by DatagramSocket

1. //DReceiver.java  
2. import java.net.*;  
3. public class DReceiver{  
4.   public static void main(String[] args) throws Exception {  
5.     DatagramSocket ds = new DatagramSocket(3000);  
6.     byte[] buf = new byte[1024];  
7.     DatagramPacket dp = new DatagramPacket(buf, 1024);  
8.     ds.receive(dp);  
9.     String str = new String(dp.getData(), 0, dp.getLength());  
10.     System.out.println(str);  
11.     ds.close();  
12.   }  
13. }