+int para_select(int n, fd_set *readfds, fd_set *writefds,
+ struct timeval *timeout_tv);
+int mark_fd_nonblock(int fd);
+void para_fd_set(int fd, fd_set *fds, int *max_fileno);
+__must_check int para_fread(void *dest, size_t nbytes, size_t nmemb, FILE *stream);