Parameter overwritten

Internal port overwritten and ignored when specified, because of this code:
```

# default internal port to local port if internal ip is local ip
if not self.internal_port and self.internal_ip == self.get_local_ip():
    internal_port = self.get_open_local_port()
# otherwise random port
else:
    internal_port = self._get_random_dynamic_port()
```