Fill in the name (myserver), external port number (80,8080 ... any one), protocol (TCP), internal port number (80), protocol (TCP), IP address of internal server (192.168.1.99).
Go back to the router's status page, check the router's dynamic external network address (for example, 234.23. 1 12.56), and then log in to the external network (not on the current computer) 234.23.12.56: 8080. Check the results.
However, your mobile broadband is connected to the external network by dialing the number, and the external network address 234.23. 1 12.56 will change at any time. This method is not suitable for establishing long-term mapping. It's better to change it in other ways.