How to ensure the connection of the server with a large number of devices?

Question

Computer networks

Good afternoon, I am developing an information system that will consist of a central server and several devices. The server can send commands to devices and receive a response from them.
I can’t think of a better way to connect the server and devices, because the dedicated ip address will be only for the server, but not for devices.
How would you provide such a connection? I would not want to load a weak server with a large number of requests from devices that simply check if the server has new commands for them.
With feedback, everything is simple, the device simply sends data to the specified ip.
Thanks for answers!
PS We can assume that I can program the devices as I want.

Answer 1

Use websocket or long pooling.

Answer 2

The server can only be loaded with keep alive messages from devices. Upon updating the data, the server will give the devices information on the last known and active IP. Actually, transferring data simultaneously to a large number of devices will be a problem.