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

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class SimpleTcpClient {
    public final static String PASSWORD = "password";

    public static void main(String args[]) throws Exception {
        String message = "A Secret Message";

        // Create connection
        InetAddress serverAddress = InetAddress.getByName("localhost");
        int serverPort = 7896;
        Socket socket = new Socket(serverAddress, serverPort);

        // Create Key
        byte key[] = PASSWORD.getBytes();
        DESKeySpec desKeySpec = new DESKeySpec(key);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        SecretKey secretKey = keyFactory.generateSecret(desKeySpec);

        // Init the Cipher
        Cipher desCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        desCipher.init(Cipher.ENCRYPT_MODE, secretKey);

        // Create streams
        OutputStream os = socket.getOutputStream();
        CipherOutputStream cos = new CipherOutputStream(os, desCipher);

        // Print the message to the outputstream
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(cos));
        pw.println(message);
        pw.close();

        // Send message
        cos.close();

        // close socket
        socket.close();
    }
}

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

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class SimpleTcpServer {
    public final static String PASSWORD = "password";

    public static void main(String args[]) throws Exception {
        // Create connection
        int serverPort = 7896;
        ServerSocket serverSocket = new ServerSocket(serverPort);
        Socket socket = serverSocket.accept(); // blocking call

        // Create Key
        byte key[] = PASSWORD.getBytes();
        DESKeySpec desKeySpec = new DESKeySpec(key);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        SecretKey secretKey = keyFactory.generateSecret(desKeySpec);

        // Init the Cipher
        Cipher desCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        desCipher.init(Cipher.DECRYPT_MODE, secretKey);

        // Create the encrypted inputstream
        InputStream is = socket.getInputStream();
        CipherInputStream cis = new CipherInputStream(is, desCipher);

        // Read the message
        BufferedReader br = new BufferedReader(new InputStreamReader(cis));
        System.out.println(br.readLine());
    }
}