// server_rcvlowat_demo.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define PORT 9090
#define RCVLOWAT_VAL 10

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

    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) { perror("socket"); exit(1); }

    // Set SO_RCVLOWAT
    if (setsockopt(server_fd, SOL_SOCKET, SO_RCVLOWAT,
                   &(int){RCVLOWAT_VAL}, sizeof(int)) < 0) {
        perror("setsockopt SO_RCVLOWAT");
    } else {
        printf("[Server] SO_RCVLOWAT set to %d\n", RCVLOWAT_VAL);
    }

    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"); exit(1);
    }

    listen(server_fd, 3);
    printf("[Server] Listening on port %d...\n", PORT);

    client_fd = accept(server_fd, (struct sockaddr *)&address, &addrlen);
    printf("[Server] Client connected!\n");

    char buffer[1024] = {0};
    printf("[Server] Waiting for at least %d bytes...\n", RCVLOWAT_VAL);

    int valread = recv(client_fd, buffer, sizeof(buffer), 0);
    if (valread < 0) perror("recv");
    else printf("[Server] recv() returned %d bytes: %.*s\n", valread, valread, buffer);

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