BitStuffingUDPServer.java

import java.net.*;

class BitStuffingUDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket serverSocket = new DatagramSocket(6789);
        System.out.println("UDP Bit Stuffing Server is running on port 6789...");

        byte[] receiveBuffer = new byte[1024];
        byte[] sendBuffer;
        DatagramPacket sendPacket;

        while (true) {
            DatagramPacket receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);
            serverSocket.receive(receivePacket);
            InetAddress clientAddress = receivePacket.getAddress();
            int clientPort = receivePacket.getPort();

            while (true) {
                
                
                receiveBuffer = new byte[1024]; // Clear buffer
                receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);
                serverSocket.receive(receivePacket);
                String inputData = new String(receivePacket.getData(), 0, receivePacket.getLength());

                

                // Perform Bit Stuffing
                String stuffedData = bitStuff(inputData);
                System.out.println("Stuffed Data: " + stuffedData);

                // Send stuffed data back to client
                sendBuffer = ("Stuffed Data: " + stuffedData + "\n").getBytes();
                sendPacket = new DatagramPacket(sendBuffer, sendBuffer.length, clientAddress, clientPort);
                serverSocket.send(sendPacket);

                // Perform Bit unstuffing
                String originalData = bitUnstuff(stuffedData);
                System.out.println("De-Stuffed Data: " + originalData);

                
            }
        }
    }

    // Method to perform bit stuffing
    public static String bitStuff(String data) {
        StringBuilder stuffedData = new StringBuilder("01111110"); // Start flag byte
        int count = 0;

        for (int i = 0; i < data.length(); i++) {
            if (data.charAt(i) == '1') {
                count++;
                stuffedData.append("1");
                if (count == 5) {
                    stuffedData.append("0"); // Stuff a '0' after five consecutive '1's
                    count = 0;
                }
            } else {
                stuffedData.append("0");
                count = 0;
            }
        }
        stuffedData.append("01111110"); // End flag byte
        return stuffedData.toString();
    }

    // Method to perform bit unstuffing
    public static String bitUnstuff(String data) {
        StringBuilder unstuffedData = new StringBuilder();
        int count = 0;

        // Remove flag bytes first
        String actualData = data.substring(8, data.length() - 8);

        for (int i = 0; i < actualData.length(); i++) {
            if (actualData.charAt(i) == '1') {
                count++;
                unstuffedData.append("1");
                if (count == 5 && i + 1 < actualData.length() && actualData.charAt(i + 1) == '0') {
                    i++; // Skip the stuffed '0'
                    count = 0;
                }
            } else {
                unstuffedData.append("0");
                count = 0;
            }
        }
        return unstuffedData.toString();
    }
}