// server.c (debug version)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>

#define PORT 5000

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    socklen_t addrlen = sizeof(address);
    char buffer[1024];

    const char *ack = "ACK";

    // Create socket
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) { perror("socket failed"); exit(EXIT_FAILURE); }

    // Disable Nagle
    if (setsockopt(server_fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt)) < 0)
        perror("setsockopt TCP_NODELAY failed");

    // Bind
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    if (listen(server_fd, 3) < 0) {
        perror("listen failed");
        exit(EXIT_FAILURE);
    }

    printf("Server listening on port %d...\n", PORT);

    new_socket = accept(server_fd, (struct sockaddr*)&address, &addrlen);
    if (new_socket < 0) { perror("accept failed"); exit(EXIT_FAILURE); }
    printf("Client connected!\n");

    while (1) {
        int valread = read(new_socket, buffer, sizeof(buffer) - 1);
        if (valread > 0) {
            buffer[valread] = '\0';
            printf("Received: %s\n", buffer);
            fflush(stdout);

            send(new_socket, ack, strlen(ack), 0);
            printf("Sent: ACK\n");
        } else if (valread == 0) {
            printf("Client disconnected.\n");
            break;
        } else {
            perror("read failed");
            break;
        }
    }

    close(new_socket);
    close(server_fd);
    return 0;
}