The target point is unreachable

how to know the target point unreachable?

Can you explain further what exactly you are trying to achieve?

If you want to determine weather a robot target is reachable by the robot you will need to do an inverse-kinematics calculation.

I control robot using port 30003, write C++ using urscript, like this
I want to know whether the target point is reachable before I send the target point to robot.
Beside I write a IK program to judge the target point is reachable, if I can use script like is_within_safety_limits(pose) ,get_inverse_kin_has_solution to judge? Can I get the return value in PC via port 30003?