Numerical controller with DNC operation function using a plurality of communication lines

A numerical controller capable of DNC operation using an NC program acquired from a host through a communication path, the numerical controller comprising:

• a numerical control unit that controls a machine tool based on the NC program;
• a plurality of communication units that use different communication paths to receive the NC program;
• and
• a DNC operation management unit that supplies the NC program received by the communication units to the numerical control unit, wherein
• each of the plurality of communication units comprises:
• a reception data buffer that stores the NC program;
• and
• an NC program reception unit that receives the NC program from the host to store the NC program in the reception data buffer, wherein
• the DNC operation management unit
• acquires the NC program from the reception data buffer included in one of the plurality of communication units to supply the NC program to the numerical control unit and
• comprises a reception management unit that switches an acquisition destination of the NC program to the reception data buffer of another communication unit when a communication failure of the communication path used by the one of the plurality of communication units is detected, and wherein
• the reception management unit detects the communication failure of the communication path used by the communication unit based on a remaining amount of the NC program stored in the reception data buffer of the communication unit being an acquisition destination of the NC program.