Miscellany

import java.io.*;
import java.net.*;
class UDPClient {
public static void main(String args[]) throws Exception
{
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket(5432);
InetAddress IPAddress = InetAddress.getByName("127.0.0.1");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}
}






import java.io.*;
import java.net.*;
class UDPServer {
public static void main (String args[ ]) throws Exception
{
DatagramSocket serverSocket = new DatagramSocket( 9876);
byte[ ] receiveData = new byte[1024];
byte[ ] sendData = new byte[1024];
while(true)
{
DatagramPacket receivePacket = new DatagramPacket(
receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData());
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket(
sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
}
}
}




import java.io.*;
import java.net.*;

class TCPServer {

  public static void main(String argv[]) throws Exception
    {
      String clientSentence;
      String capitalizedSentence;

      ServerSocket welcomeSocket = new ServerSocket(6789);
 
      while(true) {
 
                   Socket connectionSocket = welcomeSocket.accept();

           BufferedReader inFromClient =
             new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));

           DataOutputStream  outToClient =
             new DataOutputStream(connectionSocket.getOutputStream());

           clientSentence = inFromClient.readLine();

           capitalizedSentence = clientSentence.toUpperCase() + '\n';

           outToClient.writeBytes(capitalizedSentence);
        }
    }
} 


import java.io.*;
import java.net.*;
class TCPClient {

    public static void main(String argv[]) throws Exception
    {
        String sentence;
        String modifiedSentence;

        BufferedReader inFromUser =
          new BufferedReader(new InputStreamReader(System.in));

        Socket clientSocket = new Socket("127.0.0.1", 6789);

       // Remember to replace the “hostname” with the workstation name or IP address

        DataOutputStream outToServer =
          new DataOutputStream(clientSocket.getOutputStream());

        BufferedReader inFromServer =
          new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

        sentence = inFromUser.readLine();

        outToServer.writeBytes(sentence + '\n');

        modifiedSentence = inFromServer.readLine();

        System.out.println("FROM SERVER: " + modifiedSentence);

        clientSocket.close();
                  
    }
}