int read_timeout(int ms, int fd, void *data, int bytes);
int read_parent(int ms);
int send_parent(int64_t value, const void *data, int bytes);
int read_child(int ms);
int send_child(int64_t value, const void *data, int bytes);
int read_timeout(int ms, int fd, void *data, int bytes);
int read_parent(int ms);
int send_parent(int64_t value, const void *data, int bytes);
int read_child(int ms);
int send_child(int64_t value, const void *data, int bytes);