Java DatagramSocket Class

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Java includes the DatagramSocket class to handle UDP (User Datagram Protocol) communication processes. UDP operates without establishing connections and offers faster transmission by not ensuring message delivery unlike TCP.

 

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The DatagramSocket serves as the tool for sending DatagramPacket objects across network connections.

Syntax

DatagramSocket socket = new DatagramSocket(); // for sending
DatagramSocket socket = new DatagramSocket(port); // for receiving

Methods of DatagramSocket

Method Description
send(DatagramPacket p) Sends a UDP packet
receive(DatagramPacket p) Receives a UDP packet
close() Closes the socket
getPort() Returns the port number
getInetAddress() Returns the destination address
isClosed() Checks if the socket is closed

Example

UDP Server (Receiver)

import java.net.*;

public class UDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9876);
        byte[] buffer = new byte[1024];

        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
        System.out.println("Server is waiting...");

        socket.receive(packet); // blocks until a packet is received

        String message = new String(packet.getData(), 0, packet.getLength());
        System.out.println("Received: " + message);

        socket.close();
    }
}

Example

UDP Client (Sender)

import java.net.*;

public class UDPClient {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket();
        String message = "Hello, UDP Server!";
        InetAddress address = InetAddress.getByName("localhost");

        byte[] buffer = message.getBytes();
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length, address, 9876);

        socket.send(packet);
        System.out.println("Packet sent.");
        socket.close();
    }
}

Output

Server Console:

Server is waiting...
Received: Hello, UDP Server!

Client Console:

 Packet sent.
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