Hello AD5XJ,
Thank you for your comment.
The information about your gateway settings is a little bit confusing; we are not sure if you have these mentioned two ports (4000 and 4023) redirected on router by your ISP or if you have admin access to the router and you are able to redirect it by yourself.
Technically, every computer in your LAN should have a specific port redirected on your router.
If you want to reach more than one computer from WAN, you must set, on the router, the port forwarding to local IP and port 4000.
For example:
first computer – WAN port 8001 forward to IP 192.168.1.10 and port 4000
second computer – WAN port 8002 forward to IP 192.168.1.11 and port 4000.
Regards
Tom