Can I override the default server_port for in-game server?

[gugu ge]

I’ve been playing DST recently and need to do manual port-forwarding, but I can’t select an external port (because of NAT).

Since I’m playing caves, I’d like to at least set a correct server_port (same with its external port) for the caves so others can connect properly. 

However, modifying server.ini doesn’t work for in-game servers: the server_port is always automatically overwritten at startup.

Is there a way to change the server_port without migrating to a Dedicated Server?

[GimplyGoose]

I'm not aware of a way to change the ports without using a dedicated server. You could look into using port triggering if your router supports it. It might be able to do what you need. Otherwise, maybe just use a dedicated server.