I'm having problems with the number of simultaneous connections in ubuntu server 20.04

I'm working with suntech st310u I have 80 devices installed with 2 hours of operation to receive the positions, only the devices that are still connected that send normally, the new connections cannot connect. More if you restart the server back to normal for an approximate time of 2 hours.

What I could understand and that when the device loses connection it comes back in another and the previous one remains open! So the connection number is low.

Have you read the optimization guide we have in the documentation section?

yes and I made the modifications, but it didn't solve it, I'll check everything again