#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>
#include <fcntl.h>
#include <errno.h>

int main(int argc, char *argv[]) {
	int sock;
	int efd;
	int one = 1;
	int port;
	int res;
	int optval;
	int optlen = sizeof(optval);

	struct sockaddr_in server;
	struct epoll_event ev;

	/* first argument is the destination addr as an ipv4 literal */
	/* second argument is the destination port */

	if (argc < 3) {
		printf("usage: %s <target_ipv4_address> <port>\n", argv[0]);
		return 1;
	}

	port = atoi(argv[2]);

	efd = epoll_create1(O_CLOEXEC);
	if (efd < 0) {
		perror("epoll_create1");
		return 1;
	}

	sock = socket(PF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP);
	if (sock < 0) {
		perror("socket");
		return 1;
	}
	if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &one, sizeof(one)) < 0) {
		perror("setsockopt");
		return 1;
	}

	server.sin_addr.s_addr = inet_addr(argv[1]);
	server.sin_family = AF_INET;
	server.sin_port = htons(port);

	res = connect(sock, (struct sockaddr *)&server, sizeof(server));

	if (res >= 0) {
		printf("connect succeeded, not interesting\n");
		return 1;
	}

	if (errno != EINPROGRESS) {
		perror("connect");
		return 1;
	}

	/* try to "miss" the epoll event */
	sleep(5);

	ev.events = EPOLLIN|EPOLLOUT|EPOLLET|EPOLLRDHUP;
	ev.data.fd = sock;

	if (epoll_ctl(efd, EPOLL_CTL_ADD, sock, &ev) < 0) {
		perror("epoll_ctl");
		return 1;
	}

	res = epoll_wait(efd, &ev, 1, 10000);
	if (res < 0) {
		perror("epoll_wait");
		return 1;
	}

	if (res == 0) {
		printf("no events\n");
		return 1;
	}

	if (res > 1) {
		printf("impossible number of events: %d\n", res);
	}

	if (getsockopt(ev.data.fd, SOL_SOCKET, SO_ERROR, &optval, &optlen) < 0) {
		perror("getsockopt");
	}
	close(ev.data.fd);

	printf("socket fd %d has errno %d\n", ev.data.fd, optval);
}