int set_option(int, int, const void *, socklen_t);
int get_option(int, int, void *, socklen_t *) const;
unsigned do_write(const char *, unsigned);
int set_option(int, int, const void *, socklen_t);
int get_option(int, int, void *, socklen_t *) const;
unsigned do_write(const char *, unsigned);