python, tcpServer tcpClient, [WinError 10061]

when I try to run tcpServer and tcpClient on the same local network, it works, but I can't run them on the external network. The OS refuses the connection.

''Main builtins.ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it''

• I checked whether tcpServer is running or not using netstat, and it is in the listening state.

What am I supposed to do?

Thanks