package tcp;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @author kokotchy
 */
public class TCPServer {
    private ServerSocket welcomeSocket;
   
   
    public static void main(String[] args) {
        TCPServer server = new TCPServer();
    }
   
    public TCPServer() {
        String clientSentence;
        String capitalizedSentence;
        try {
            welcomeSocket = new ServerSocket(6789);
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("Start listening on port 6789");
        while (true) {
            try {
                Socket connectionSocket = welcomeSocket.accept();
                System.out.println("Connection from "+connectionSocket.getRemoteSocketAddress()+" on port "+connectionSocket.getLocalPort());
                BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
                DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
                clientSentence = inFromClient.readLine();
                System.out.println("Receive : "+clientSentence);
                capitalizedSentence = clientSentence.toUpperCase() + "\n";
                System.out.println("Send : "+capitalizedSentence);
                outToClient.writeBytes(capitalizedSentence);
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;

/**
 * @author kokotchy
 */
public class TCPClient {
    private Socket clientSocket;
    private DataOutputStream outToServer = null;
   
    public static void main(String[] args) {
        TCPClient client = new TCPClient();
    }
   
    public TCPClient() {
        String sentence = null;
        String modifiedSentence = null;
        BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
        try {
            clientSocket = new Socket("127.0.0.1",6789);
            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();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

package udp;

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

/**
 * @author kokotchy
 */
public class UDPServer {

    public static void main(String[] args) {
        UDPServer server = new UDPServer();
    }
   
    public UDPServer() {
        try {
            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);
            }
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

package udp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

/**
 * @author kokotchy
 */
public class UDPClient {

    public static void main(String[] args) {
        UDPClient client = new UDPClient();
    }
   
    public UDPClient() {
        try {
            BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
            DatagramSocket clientSocket = new DatagramSocket();
            InetAddress IPAddress = InetAddress.getByName("localhost");
            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();
        }
        catch (SocketException e) {
            e.printStackTrace();
        }
        catch (UnknownHostException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}