#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/socket.h>

int connect_wait (
	int sockno,
	struct sockaddr * addr,
	size_t addrlen,
	struct timeval * timeout)
{
	int res, opt;

	// get socket flags
	if ((opt = fcntl (sockno, F_GETFL, NULL)) < 0) {
		return -1;
	}

	// set socket non-blocking
	if (fcntl (sockno, F_SETFL, opt | O_NONBLOCK) < 0) {
		return -1;
	}

	// try to connect
	if ((res = connect (sockno, addr, addrlen)) < 0) {
		if (errno == EINPROGRESS) {
			fd_set wait_set;

			// make file descriptor set with socket
			FD_ZERO (&wait_set);
			FD_SET (sockno, &wait_set);

			// wait for socket to be writable; return after given timeout
			res = select (sockno + 1, NULL, &wait_set, NULL, timeout);
		}
	}
	// connection was successful immediately
	else {
		res = 1;
	}

	// reset socket flags
	if (fcntl (sockno, F_SETFL, opt) < 0) {
		return -1;
	}

	// an error occured in connect or select
	if (res < 0) {
		return -1;
	}
	// select timed out
	else if (res == 0) {
		errno = ETIMEDOUT;
		return 1;
	}
	// almost finished...
	else {
		socklen_t len = sizeof (opt);

		// check for errors in socket layer
		if (getsockopt (sockno, SOL_SOCKET, SO_ERROR, &opt, &len) < 0) {
			return -1;
		}

		// there was an error
		if (opt) {
			errno = opt;
			return -1;
		}
	}

	return 0;
}