#include <sys/poll.h>
#include <netinet/in.h>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sys/socket.h>
#include <unistd.h>
#define PORT 40000

static int server_fd;
static struct sockaddr_in sock_address;

static void createServer() {
    int opt = 1;

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

//    // Forcefully attaching socket to the port 8080
//    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
//        perror("setsockopt");
//        exit(EXIT_FAILURE);
//    }

    sock_address.sin_family = AF_INET;
    sock_address.sin_addr.s_addr = INADDR_ANY;
    sock_address.sin_port = htons(PORT);

    // Forcefully attaching socket to the port
    if (bind(server_fd, (sockaddr*)&sock_address, sizeof(sock_address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
    if (listen(server_fd, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }
}

int openSocket() {
    int sock;
    int addrlen = sizeof(sock_address);

    if ((sock = accept(server_fd, (sockaddr*)&sock_address, (socklen_t*)&addrlen)) < 0) {
        perror("accept");
        exit(EXIT_FAILURE);
    }

    return sock;
}

static struct pollfd fdList[2];

int main() {
    createServer();

    fdList[0].fd = STDIN_FILENO;
    fdList[0].events = POLLIN;

    while (true) {
        int sock = openSocket();
        printf("Connected fd=%d\n", sock);
        fdList[1].fd = sock;
        fdList[1].events = POLLIN;

        while (true) {
            if (poll(fdList, 2, -1) < 1) {
                continue;
            }

            if (fdList[1].revents & POLLNVAL) {
                printf("POLLNVAL\n");
                break;
            }

            if (fdList[1].revents & POLLHUP) {
                printf("closed by peer\n");
                close(fdList[1].fd);
                break;
            }

            if (fdList[1].revents & POLLIN) {
                char buff[1024];
                ssize_t size = read(fdList[1].fd, buff, sizeof(buff));
                if (size < 0) {
                    printf("closed by peer\n");
                    break;
                }

                write(STDOUT_FILENO, buff, size);
            }

            // получены данные из STDIN
            if (fdList[0].revents & POLLIN) {
                char buff[1024];
                ssize_t size = read(fdList[0].fd, buff, sizeof(buff));
                if (size < 0) {
                    printf("stdin EOL\n");
                    return 0;
                }

                write(fdList[1].fd, buff, size);
            }
        }

        // closing the connected socket
        close(sock);
        // closing the listening socket
        shutdown(server_fd, SHUT_RDWR);
    }
}