Python socket ipv6 over network not working

I am trying to connect a server to a client in python with sockets. The problem is that with ipv6 binding, it works on my local network. What I want is to connect it to another network. These programs are written in Python 3

Here is the code of server.py:

import socket

HOST = someip
PORT = someport

server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
server.bind((HOST, PORT))

server.listen()

Source code of client.py:

import socket
HOST = someip
PORT = someport

client = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
client.connect((HOST, PORT))

I think it is a port forwarding problem. I know the code does nothing right now, but I want to first establish the connection.

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