import socket

localIP     = "127.0.0.1"
localPort   = 20001
bufferSize  = 1024

msgFromServer       = "Hello UDP Client"
bytesToSend         = str.encode(msgFromServer)

# Create a datagram socket
UDPServerSocket = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
# Bind to address and ip

UDPServerSocket.bind((localIP, localPort))
print("UDP server up and listening")

# Listen for incoming datagrams
while(True):
    bytesAddressPair = UDPServerSocket.recvfrom(bufferSize)
    message = bytesAddressPair[0]
    address = bytesAddressPair[1]
    
    clientMsg = "Message from Client:{}".format(message)
    clientIP  = "Client IP Address:{}".format(address)
    
    print(clientMsg)
    print(clientIP)

    # Sending a reply to client
    UDPServerSocket.sendto(bytesToSend, address)

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
  
public class udpBaseServer_2
{
    public static void main(String[] args) throws IOException
    {
        // Step 1 : Create a socket to listen at port 1234
        DatagramSocket ds = new DatagramSocket(1234);
        byte[] receive = new byte[65535];
  
        DatagramPacket DpReceive = null;
        while (true)
        {
  
            // Step 2 : create a DatgramPacket to receive the data.
            DpReceive = new DatagramPacket(receive, receive.length);
  
            // Step 3 : revieve the data in byte buffer.
            ds.receive(DpReceive);
  
            System.out.println("Client:-" + data(receive));
  
            // Exit the server if the client sends "bye"
            if (data(receive).toString().equals("bye"))
            {
                System.out.println("Client sent bye.....EXITING");
                break;
            }
  
            // Clear the buffer after every message.
            receive = new byte[65535];
        }
    }
  
    // A utility method to convert the byte array
    // data into a string representation.
    public static StringBuilder data(byte[] a)
    {
        if (a == null)
            return null;
        StringBuilder ret = new StringBuilder();
        int i = 0;
        while (a[i] != 0)
        {
            ret.append((char) a[i]);
            i++;
        }
        return ret;
    }
}

package main

import (
	"fmt"
	"log"
	"net"
	"time"
)

func main() {
	// listen to incoming udp packets
	udpServer, err := net.ListenPacket("udp", ":1053")
	if err != nil {
		log.Fatal(err)
	}
	defer udpServer.Close()

	for {
		buf := make([]byte, 1024)
		_, addr, err := udpServer.ReadFrom(buf)
		if err != nil {
			continue
		}
		go response(udpServer, addr, buf)
	}

}

func response(udpServer net.PacketConn, addr net.Addr, buf []byte) {
	time := time.Now().Format(time.ANSIC)
	responseStr := fmt.Sprintf("time received: %v. Your message: %v!", time, string(buf))

	udpServer.WriteTo([]byte(responseStr), addr)
}