P-Box.

[ SENDER SIDE ]

import java.io.*;
import java.net.*;
public class sender
{
public static void main(String args[])throws Exception
{
int i,pos;
String input="",output="",key="241503";
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
Socket soc=new Socket("localhost",3030);
DataOutputStream dos=new DataOutputStream(soc.getOutputStream());
System.out.print("Enter Data To Send [length = 6] : ");
input=br.readLine();
for(i=0;i<input.length();i++)
{
pos=Integer.parseInt(key.charAt(i)+"");
output=output+input.charAt(pos);
}
System.out.println("Encrypted Data is "+output);
dos.writeUTF(output);
}
}

[ RECEIVER SIDE ]

import java.io.*;
import java.net.*;
public class receiver
{
public static void main(String args[])throws Exception
{
int i,pos;
String input="",output="",key="241503";
ServerSocket ss=new ServerSocket(3030);
Socket soc=ss.accept();
DataInputStream dis=new DataInputStream(soc.getInputStream());
input=dis.readUTF();
for(i=0;i<input.length();i++)
{
pos=key.indexOf(""+i);
output=output+input.charAt(pos);
}
System.out.println("Encrypted Data is "+output);
}
}