The error message you have shared indicates that you are attempting to use NetSim's inbuilt socket interface meant for the CLI interpreter to execute various networking commands for devices in NetSim.

The recommended approach is to use dedicated TCP socket interface for interfacing with your python program.

Socket Server (NetSim):

In NetSim, you can write a socket server program that listens for incoming connections from external clients. This program can be integrated into your simulation model to start listening for connections when the simulation starts.

Socket Client (Python):

As part of your Python program, you can create a socket client that connects to the socket server implemented in NetSim. This client can then communicate with the server, exchanging information throughout the simulation.

You could check the knowledgebase https://support.tetcos.com/support/home. In the same link you could also raise a support ticket with the developers who are usually responsive.