You keep saying "without using port" and that literally just does not make sense. I think you're talking about port forwarding, and that your problem is actually that you don't know how to port forward properly.
Is a guide to port forwarding explained. If you think you're having problems with this. Port forwarding is a router configuration that defines forwarding rules for your network.
So basically it tells your router which machine to forward network requests to when packets come in. Without this step, your network has no idea what to do with incoming network packets. This is absolutely required by basically any server hosting application. Sometimes, disabling your router's firewall just simply isn't enough because port forwarding is more than just a network security configuration, it's a network routing configuration..
Edit: Also just reread something jc posted about having multiple routers. this is insane. but like, if you can't modify your network layout, you're gonna have to make port forwarding rules on each individual router. So you'll have to tell the router connected to your modem, to forward packets to the router connected to your other route. then tell the router that's connected to your computer that you just forwarded to from the router to forward packets to the hosting pc.
Edit2: So I'm going out of town this weekend, but when i get back on Sunday, if you haven't figured this out, i can help you set it up if you join my discord server. https://discord.gg/szADqTM