import java.io.
*;
import java.net.*;
public class SlidingReceiver {
public static void main(String[] args) throws Exception {
DatagramSocket socket = new DatagramSocket(9876);
byte[] buffer = new byte[1024]; // Increased buffer size to receive packet data
int expectedPacket = 0; // Track the next expected packet
boolean[] receivedPackets = new boolean[256]; // Array to track received packets
while (true) {
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
String receivedData = new String(packet.getData(), 0, packet.getLength());
// Split the received data into sequence number and character
String[] parts = receivedData.split(":");
int seqNum = Integer.parseInt(parts[0]) ; // Convert to 0-based index
char receivedChar = parts[1].charAt(0);
// Print received character and its sequence number
System.out.println("Received packet: " + receivedChar + " (Received Sequence Number: " +
seqNum + ")");
// Check if the packet was already received
if (!receivedPackets[seqNum]) {
receivedPackets[seqNum] = true; // Mark this packet as received
// Send ACK for the received packet
byte[] ackData = new byte[1];
ackData[0] = (byte) expectedPacket; // Acknowledgment number
DatagramPacket ackPacket = new DatagramPacket(ackData, ackData.length,
packet.getAddress(), packet.getPort());
socket.send(ackPacket);
System.out.println("Sent ACK: " + expectedPacket);
expectedPacket++; // Move to the next expected packet
} else {
System.out.println("Duplicate packet received: " + receivedChar);
import java.io.*;
import java.net.*;
public class SlidingSender {
public static void main(String[] args) throws Exception {
DatagramSocket socket = new DatagramSocket();
InetAddress receiverAddress = InetAddress.getByName("localhost");
int receiverPort = 9876;
int windowSize = 4;
String message = "Hello, Sliding Window!";
byte[] data = message.getBytes();
int base = 0;
boolean[] sentPackets = new boolean[data.length]; // Track sent packets
while (base < data.length) {
// Send packets in the current window
for (int i = base; i < base + windowSize && i < data.length; i++) {
if (!sentPackets[i]) { // Only send if not already sent
// Create a packet with sequence number and character
String packetData = i + ":" + (char) data[i]; // Sequence number:character
DatagramPacket packet = new DatagramPacket(packetData.getBytes(),
packetData.length(), receiverAddress, receiverPort);
socket.send(packet);
sentPackets[i] = true; // Mark this packet as sent
System.out.println("Sent packet: " + packetData);
// Wait for ACK
byte[] ackBuffer = new byte[1];
DatagramPacket ackPacket = new DatagramPacket(ackBuffer, ackBuffer.length);
socket.receive(ackPacket);
int ack = ackBuffer[0];
System.out.println("Received ACK: " + ack);
if (ack >= base) {
base = ack + 1; // Move the base forward
socket.close();
