I need an explaining for each step in this code and the reason of it. import java.io.*; import java.net.*; import java.util.Base64; import javax.crypto.Cipher; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; public class TCPServer { /** * args the command line arguments */ public static void main(String[] args) { // TODO code application logic here int port = 6000; try (ServerSocket serverSocket = new ServerSocket(port)) { System.out.println("Server is listening on port " + port); while (true) { System.out.println("waiting for a client to connect."); Socket socket = serverSocket.accept(); System.out.println("New client connected"); DataInputStream dis = new DataInputStream(socket.getInputStream()); DataOutputStream dos = new DataOutputStream(socket.getOutputStream()); int option; String text; System.out.println("Waiting for mode."); option=dis.readInt(); switch(option) { case 1: System.out.println("open mode activated."); dos.writeUTF("open mode activated."); do { text=dis.readUTF(); System.out.println("client sent: " + text); dos.writeUTF(text); }while(!text.equals("exit")); break; case 2: System.out.println("secure mode activated."); dos.writeUTF("secure mode activated."); String keyString="1234567890123456"; String ivString="6543210987654321"; IvParameterSpec iv=new IvParameterSpec(ivString.getBytes("UTF-8")); SecretKeySpec key=new SecretKeySpec(keyString.getBytes("UTF-8"),"AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING"); cipher.init(Cipher.DECRYPT_MODE, key, iv); String plainString=""; do { text=dis.readUTF(); System.out.println("client sent: " + text); byte[] plainText = cipher.doFinal(Base64.getDecoder().decode(text)); plainString=new String(plainText); System.out.println("plain text is: " + plainString); dos.writeUTF(text); }while(!plainString.equals("exit")); break; case 3: socket.close(); System.out.println("client has disconnected"); break; } } } catch (Exception ex) { /*System.out.println("Server exception: " + ex.getMessage()); ex.printStackTrace(); */ System.out.println("port : " + port); } } } .

1. I need an explaining for each step in this code and the reason of it.
import java.io.*;
import java.net.*;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class TCPServer {
/**
* args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
int port = 6000;
try (ServerSocket serverSocket = new ServerSocket(port)) {
System.out.println("Server is listening on port " + port);
while (true) {
System.out.println("waiting for a client to connect.");
Socket socket = serverSocket.accept();
System.out.println("New client connected");
DataInputStream dis = new DataInputStream(socket.getInputStream());
DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
int option;
String text;
System.out.println("Waiting for mode.");
option=dis.readInt();
switch(option)
{
case 1:
System.out.println("open mode activated.");
dos.writeUTF("open mode activated.");
do
{
text=dis.readUTF();
System.out.println("client sent: " + text);
dos.writeUTF(text);

2. }while(!text.equals("exit"));
break;
case 2:
System.out.println("secure mode activated.");
dos.writeUTF("secure mode activated.");
String keyString="1234567890123456";
String ivString="6543210987654321";
IvParameterSpec iv=new IvParameterSpec(ivString.getBytes("UTF-8"));
SecretKeySpec key=new SecretKeySpec(keyString.getBytes("UTF-8"),"AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, key, iv);
String plainString="";
do
{
text=dis.readUTF();
System.out.println("client sent: " + text);
byte[] plainText = cipher.doFinal(Base64.getDecoder().decode(text));
plainString=new String(plainText);
System.out.println("plain text is: " + plainString);
dos.writeUTF(text);
}while(!plainString.equals("exit"));
break;
case 3:
socket.close();
System.out.println("client has disconnected");
break;
}
}
} catch (Exception ex) {
/*System.out.println("Server exception: " + ex.getMessage());
ex.printStackTrace();
*/
System.out.println("port : " + port);
}
}
}