ENTITY* is a POINTER to an entity object. The pointer is ONLY valid on the system that created it. In your case the server. Sending the pointer to another system will result in a dangling pointer and a crash or unexpected behavior. You have to send the clients the information they need to create their own entities (and pointers).

edit:// If you have synchronised entities make an array with handles instead of pointers. I think they are valid over network.

edit2:// Furthermore you need send_data_id, as send_var_id only sends one var (4 Byte).