GodotTicTacToe/scripts/MainMenu.cs

using Godot;
using System;

public class MainMenu : Panel {

    private Net Net;

    private LineEdit IPAddressEdit;
    private LineEdit PortEdit;

    public override void _Ready() {
        Net = (Net) GetNode("/root/Net");
        var IPAddressNode = GetNode("IPAddress");
        var PortNode = GetNode("Port");
        if (IPAddressNode is LineEdit) {
            IPAddressEdit = (LineEdit) IPAddressNode;
        }
        if (PortNode is LineEdit) {
            PortEdit = (LineEdit) PortNode;
        }
    }

    private void OnLaunchServer() {
        GD.print("Launch Server!");
        string address;
        int port;
        SetAddressAndPort(out address, out port, "*", 7070);
        Net.StartServer(address, port);
    }


    private void OnLaunchClient() {
        GD.print("Launch Client!");
        string address;
        int port;
        SetAddressAndPort(out address, out port, "localhost", 7070);
        Net.StartClient(address, port);
    }

    private void SetAddressAndPort(out string address, out int port, string defaultAddress, int defaultPort) {
        if (IPAddressEdit == null || IPAddressEdit.GetText() == "") {
            address = defaultAddress;
        } else {
            address = IPAddressEdit.GetText();
        }
        port = defaultPort;
        if (PortEdit != null && PortEdit.GetText() != "") {
            //port =  PortEdit.GetText();
            int temp_port;
            Int32.TryParse(PortEdit.GetText(), out temp_port);
            if (temp_port > 80) {
                port = temp_port;
            }
        }
    }
}