FD_SETSIZE
#ifndef FD_SETSIZE
unsigned long fds[(FD_SETSIZE + FD_SETBITMASK) / FD_SETIDXMASK];
int __size = (FD_SETSIZE+FD_SETBITMASK) / FD_SETIDXMASK;\
ret = select(FD_SETSIZE, &rfds, NULL, NULL, NULL);
rc = select(FD_SETSIZE, NULL, &wfd, NULL, tv);
for (int i = prev_fd + 1; i < FD_SETSIZE; ++i) {