Since this is a custom made dongle, I think you need to contact the ISP for help or maybe instructions posted on line. And you might look into port triggering instead of port following. Are there any help screens in your device's admin menu? I note in my Netgear router, full instructions are provided which I will copy here. though yours will likely be a bit different.
Port Forwarding / Port Triggering Help
Port triggering is an advanced feature that you can use for gaming and other Internet applications. Port forwarding can typically be used to enable similar functionality, but it is static and has some limitations.
Port triggering opens an incoming port temporarily and does not require the server on the Internet to track your IP address if it is changed by DHCP, for example.
Port triggering monitors outbound traffic. When the router detects traffic on the specified outbound port, it remembers the IP address of the computer that sent the data and triggers the incoming port. Incoming traffic on the triggered port is then forwarded to the triggering computer.
Using the Port Forwarding / Port Triggering screen, you can make local computers or servers available to the Internet for different services (for example, FTP or HTTP), to play Internet games (like Quake III), or to use Internet applications (like CU-SeeMe).
Port forwarding is designed for FTP, Web server, or other server-based services. Once port forwarding is set up, requests from the Internet are forwarded to the proper server.
Port triggering allows requests from the Internet only after a designated port is triggered. Port triggering applies to chat and Internet games.
Port Triggering
Note: If Disable Port Triggering box is checked, all port triggering function will be disabled but the configuration information will remain in the router.
Port Triggering Timeout
Enter a value up to 9999 minutes. The Port Triggering Timeout value controls the inactivity timer for the designated inbound port(s). The inbound port(s) will be closed when the inactivity timer expires.
For Internet Games or Applications
Before starting, you'll need to know which service, application or game you'll be configuring. Also, you'll need to have the outbound port ( triggering port ) address for this game or application.
To setup a computer to play Internet games or use Internet applications:
1. Click Add Service button.
2. Enter a service name in the Service Name box.
3. Under Service User, select Any (default) will allow this service to be used by everyone in your network. Otherwise, select Single address and enter the PC's IP address to restrict the service to a particular PC.
4. Select Service Type.
5. Enter the outbound port number in Triggering Port box.
6. Enter the inbound connection port information such as Connection Type, Starting Port and Ending Port boxes. These information can be obtained from the game or applications manual or support website.
7. Click Apply button.
To modify a service entry:
1. Select the entry's radio button of the table.
2. Click Edit Service.
3. Modify the service.
4. Click Apply button.
To delete a service entry:
1. Select the entry's radio button of the table.
2. Click Delete Service button.