// server_nagle.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 5000

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    socklen_t addrlen = sizeof(address);

    char buffer[1024] = {0};
    const char *ack = "ACK";

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

    // 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);

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

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

        send(new_socket, ack, strlen(ack), 0);
    }

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