Java network communication over UDP socket

net_udp_receiver.java

Directories to net_udp_receiver.java in the repository: java/cz/petrfaltus/net

package cz.petrfaltus.net;

import java.io.IOException;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import static java.lang.System.out;

public class net_udp_receiver {
    private static final int RECEIVER_PORT = 10000;
    private static final int BUFFER_SIZE = 4096;

    public static void main(String[] args) {
        out.println("UDP IPv4 datagram socket receiver");

        try {
            DatagramSocket socket = new DatagramSocket(RECEIVER_PORT);
            out.println("- socket created and bound on port " + RECEIVER_PORT);

            byte[] buffer = new byte[BUFFER_SIZE];

            boolean stop = false;
            while (stop == false) {
                DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

                socket.receive(packet);
                String msg = new String(packet.getData(), 0, packet.getLength());
                InetAddress peer = packet.getAddress();
                out.println("- message " + msg.length() + "B of " + packet.getLength() + "B received from " + peer.getHostAddress() + ":" + packet.getPort() + " on port " + socket.getLocalPort());
                out.println("|" + msg + "|");

                if (msg.equals("stop")) {
                    // received message "stop" to stop the receiver
                    stop = true;
                }
            }

            socket.close();
            out.println("- socket closed");
        } catch (IOException e) {
            out.println("- " + e);
        }
    }
}

net_udp_sender.java

package cz.petrfaltus.net;

import java.io.IOException;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import java.text.DateFormat;
import java.text.SimpleDateFormat;

import java.util.Date;

import static java.lang.System.out;

public class net_udp_sender {
    private static final String RECEIVER_ADDRESS = "127.0.0.1";
    private static final int RECEIVER_PORT = 10000;

    public static void main(String[] args) {
        out.println("UDP IPv4 datagram socket sender");

        try {
            DatagramSocket socket = new DatagramSocket();
            out.println("- socket created");

            String msg;
            if (args.length > 0) {
                msg = args[0]; // message is the first parameter, for example "stop" to stop the receiver
            } else {
                Date now = new Date();
                DateFormat date_format = new SimpleDateFormat("d.M.yyyy 'in' H:mm:ss");

                msg = "This is Java message sent at " + date_format.format(now);
            }
            out.println("|" + msg + "|");

            byte[] buffer = msg.getBytes();
            InetAddress receiver_address = InetAddress.getByName(RECEIVER_ADDRESS);
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length, receiver_address, RECEIVER_PORT);

            InetAddress peer = packet.getAddress();
            out.println("- for " + peer.getHostAddress() + ":" + packet.getPort() + " bound on port " + socket.getLocalPort());

            socket.send(packet);
            out.println("- message " + buffer.length + "B of " + msg.length() + "B sent to " + RECEIVER_ADDRESS + ":" + RECEIVER_PORT);

            socket.close();
            out.println("- socket closed");
        } catch (IOException e) {
            out.println("- " + e);
        }
    }
}

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