// tcp_server_congestion.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>

#define PORT 9090
#define BUF_SIZE 1024

int main() {
    int server_fd, client_fd;
    struct sockaddr_in addr;
    socklen_t addrlen = sizeof(addr);
    char buffer[BUF_SIZE];
    const char *message = "Hello from server with congestion control\n";

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

    // Bind
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port = htons(PORT);

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

    // Listen
    if (listen(server_fd, 5) < 0) {
        perror("Listen failed");
        exit(EXIT_FAILURE);
    }

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

    // Accept
    if ((client_fd = accept(server_fd, (struct sockaddr *)&addr, &addrlen)) < 0) {
        perror("Accept failed");
        exit(EXIT_FAILURE);
    }

    // Get current congestion algorithm
    char cong[16];
    socklen_t len = sizeof(cong);
    if (getsockopt(client_fd, IPPROTO_TCP, TCP_CONGESTION, cong, &len) == 0) {
        printf("Current congestion algorithm: %s\n", cong);
    }

    // Change congestion algorithm (example: reno)
    const char *new_cong = "reno";
    if (setsockopt(client_fd, IPPROTO_TCP, TCP_CONGESTION, new_cong, strlen(new_cong)) != 0) {
        perror("setsockopt TCP_CONGESTION");
    } else {
        printf("Switched to congestion algorithm: %s\n", new_cong);
    }

    // Send data
    send(client_fd, message, strlen(message), 0);

    // Receive something
    int n = recv(client_fd, buffer, BUF_SIZE, 0);
    if (n > 0) {
        buffer[n] = '\0';
        printf("Received from client: %s\n", buffer);
    }

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