Help!How to validate the client position in headless unity?

I am planning to develop client-server RPG. Client builds by unity, server builds by Java, and the server will deliver kinetic events to headless unity to simulation. Like random inspect player‘s position, move NPC to target point. Every clients need calculate themselves motion, send position to server per 100ms, the server check a part of them. If the position is illegal, then disconnect the client.

1. The Java server will check the distance between current position and the last position, it need less then a threshold value.

2. The headless unity need check others. Like the player can’t through the wall, jump higher then other players, and other things I didn’t think of.

My question is the headless unity how to validate player’s discrete position?