int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *serial);
int sd_bus_send_with_reply(sd_bus *bus, sd_bus_message *m, sd_message_handler_t callback, void *userdata, uint64_t usec, uint64_t *serial);
int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *serial);
int sd_bus_send_with_reply(sd_bus *bus, sd_bus_message *m, sd_message_handler_t callback, void *userdata, uint64_t usec, uint64_t *serial);