The phrase likely refers to a service or application running on your local machine (port 11501 ) that is configured to accept connections only from your own system (i.e., localhost / 127.0.0.1 ), not from other devices on the network.
Another service might be using port 11501. Use a terminal command to see what is using that port: Windows: netstat -ano | findstr :11501 Linux/macOS: lsof -i :11501 3. Securing Your Localhost localhost11501 exclusive