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#include<stdio.h>
#include<string.h>
#include<sys/types.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdlib.h>
#include<sys/select.h>
#include<pthread.h>

#define timeoutValue 5
#define packetCount 10
#define windowSize 3

typedef struct Packet {
    int id;
    int sent;
} Packet;

Packet packets[packetCount];
pthread_t thread[packetCount], receivedThread;
int sockfd;
struct sockaddr_in addr;
int windowStart, windowEnd;
int nextToSend;

void* sendPacket(void* sendToPacket) {
    Packet* packet = (Packet*)sendToPacket;
    char buffer[1024];
    while (packet->sent == 0) {
        printf("Client: Sending packet %d\n", packet->id);
        bzero(buffer, 1024);
        sprintf(buffer, "%d", packet->id);
        sendto(sockfd, buffer, 1024, 0, (struct sockaddr*)&addr, sizeof(addr));
        sleep(timeoutValue);
        if (packet->sent == 0) {
            printf("Client: Timeout for packet %d\n", packet->id);
        }
    }
    return NULL;
}

void* receivePacket(void* arg) {
    char buffer[1024];
    socklen_t addr_size = sizeof(addr);
    while (1) {
        bzero(buffer, 1024);
        recvfrom(sockfd, buffer, 1024, 0, (struct sockaddr*)&addr, &addr_size);
        
        char msg[20];
        int packetID;
        sscanf(buffer, "%s%d", msg, &packetID);
        
        if (strcmp(msg, "NACK") == 0) {
            printf("Client: Received negative acknowledgment for packet %d. Sending again.\n", packetID);
            pthread_cancel(thread[packetID - 1]);
            pthread_create(&thread[packetID - 1], NULL, sendPacket, (void*)&packets[packetID - 1]);
        }
        else if (strcmp(msg, "ACK") == 0) {
            printf("Client: Received ACK for packet %d\n", packetID);
            packets[packetID - 1].sent = 1;
            if (windowStart == packetID - 1) {
                while (packets[windowStart].sent == 1 && windowStart < windowEnd) {
                    windowStart++;
                    if (windowEnd < packetCount - 1) {
                        windowEnd++;
                    }
                }
            }
        }
        else {
            printf("Client: Invalid message\n");
        }
    }
    return NULL;
}
void main() {
    for (int i = 0; i < packetCount; i++) {
        packets[i].id = i + 1;
        packets[i].sent = 0;
    }
    char* ip = "127.0.0.100";
    int port = 5570;
    socklen_t addr_size;
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("[-] Socket error");
        exit(1);
    }
    memset(&addr, '\0', sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = inet_addr(ip);
    pthread_create(&receivedThread, NULL, receivePacket, NULL);
    windowStart = 0;
    windowEnd = windowStart + windowSize - 1;
    while (windowStart <= windowEnd && windowStart < packetCount) {
        pthread_create(&thread[windowStart], NULL, sendPacket, (void*)&packets[windowStart]);
        nextToSend++;
    }
    close(sockfd);
}