A sussy Java Program that demonstrate TCP/IP connection

//Fully explanation: http://www2.ic.uff.br/~michael/kr1999/2-application/2_06-sockettcp.htm
//Note: Turn Off or Open Port on Firewall both server and client slide please
//Server-side code

package sussyserver;
import java.io.*;
import java.net.*;
public class SussyServer {

    public static void main(String[] args) throws IOException {
        String clientSentence;
        String capitalizedSentence;
        ServerSocket welcomeSocket = new ServerSocket(6789); //Replace 6789 to listening port you want
        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);
        }

    }

}

//Client-slide code

package sussyclient;
import java.io.*;
import java.net.*;

public class SussyClient {

    public static void main(String[] args) throws IOException {
        String sentence;
        String modifiedSentence;
        BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
        Socket clientSocket = new Socket("localhost", 6789); //Replace "localhost" to the IP Server. Example "69.69.69.69". The 6789 is the port - must be corressponding with server side
        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();


    }

}