tcp-rdhup.c

// date: 2020-07-06
// license: GPLv3 https://www.gnu.org/licenses/gpl-3.0.txt
// author: nanpuyue <nanpuyue@gmail.com> https://blog.nanpuyue.com

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>

#define MAX_EVENTS 10

void fail(const char *desc)
{
    perror(desc);
    exit(EXIT_FAILURE);
}

void set_nonblock(int fd)
{
    int flags = fcntl(fd, F_GETFL);
    if (flags == -1)
        fail("fcntl(F_GETFL)");

    if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
        fail("fcntl(F_SETFL)");
}

int connect_socket(const char *ip, int port)
{
    int fd = socket(AF_INET, SOCK_STREAM, 6);
    if (fd < 0)
        fail("socket");

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    if (inet_pton(AF_INET, ip, &addr.sin_addr) == 0)
    {
        printf("inet_pton: Invalid address");
        exit(EXIT_FAILURE);
    }

    if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
        fail("connect");

    set_nonblock(fd);

    return fd;
}

int main()
{
    struct epoll_event event, events[MAX_EVENTS];
    int epfd, socket, ready;

    epfd = epoll_create1(0);
    if (epfd == -1)
        fail("epoll_create1");

    socket = connect_socket("127.0.0.1", 8000);

    event.events = EPOLLRDHUP;
    event.data.fd = socket;
    if (epoll_ctl(epfd, EPOLL_CTL_ADD, socket, &event) == -1)
        fail("epoll_ctl(EPOLL_CTL_ADD)");

    for (;;)
    {
        ready = epoll_wait(epfd, events, MAX_EVENTS, -1);
        if (ready == -1)
            fail("epoll_wait");

        for (int i = 0; i < ready; ++i)
        {
            if (events[i].data.fd == socket)
            {
                printf("events: 0x%x\n", events[i].events);
                exit(EXIT_SUCCESS);
            }
        }
    }
}