Question

Practice socket programming with threads: Write an 'echo' server using UDP. (This server does not need to be multi-threaded, but make sure that you do know how to implement a multi-threaded server when asked.) Each request is handled by replying to the client with the unmodified string the client sent.

Also, write an 'echo' client to test your server. Each client will send 20 sequentially numbered messages to the server & receive the replies. This code needs to be in java.

Answer 1

import java.io.*;
import java.net.*;
public class udpserver {
public static void main(String args[]) throws Exception
{
String rev;
System.out.println("Waiting for client");
          
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
      
DatagramSocket server = new DatagramSocket(2100);

DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
server.receive(receivePacket);
      
ans =new String( receivePacket.getData());
sendData=ans.getBytes();
      
InetAddress ip = receivePacket.getAddress();
int port = receivePacket.getPort();
                 

  
                              
DatagramPacket sendPacket = new DatagramPacket(sendData,sendData.length,ip, port);
server.send(sendPacket);
  
}

import java.net.*;
import java.io.*;
public class udpclient {
public static void main(String args[]) throws Exception
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
DatagramSocket client = new DatagramSocket();
byte[] sendData = new byte [1024];
byte[] receiveData = new byte[1024];
      
InetAddress ip = InetAddress.getLocalHost();
      
System.out.println("Enter String");
String r = br.readLine();
      
sendData = r.getBytes();
      
DatagramPacket clientPacket = new DatagramPacket(sendData, sendData.length, ip,2100);
client.send(clientPacket);
      
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
client.receive(receivePacket);
      
String ans = new String(receivePacket.getData());
receiveData=ans.getBytes();
System.out.println("FROM SERVER:" +ans);
client.close();
}