Library initialisation, the global session, and rclcpp::ok().

rclcpp::init_in() boots the transport; rclcpp::shutdown_in() tears it down. rclcpp::ok() reports whether the global session is alive (false after shutdown or after a fatal transport error).

RCLCPP_TRY(rclcpp::init_in("tcp/127.0.0.1:7447"));
while (rclcpp::ok()) rclcpp::spin_once(100);
rclcpp::shutdown_in();