GL-X300B communication with control using RS485

Routers
1

We have GL-X300B control and our Android application be able to communicate via TCP/IP protocol using 192.168.8.1 port 502 with our device using RS485 connection only if our phone is connected to WiFi network GL-X300B-938. We are having installed SIM card. We are unable to connect over internet to our device. What are we missing?

2

Hi

Could you clarify what you’re trying to achieve?

If the SIM card provides a public IP—or a privately reachable IP within your enterprise network—please open the required port under Admin Panel → Network → Firewall → Open Ports on Router. You’ll then be able to access the port directly using the SIM’s IP address and port number.

If the SIM card is a standard CGNAT SIM, you’ll likely need to set up a VPN server and access the port through the VPN instead.

4

Hello!

Your phone can only reach the device on local Wi‑Fi because 192.168.8.1 is a private LAN address, not routable over the internet. To access it remotely you need to expose it safely: either get a public IP and set up port forwarding, or use a VPN/Dynamic DNS. Also check firewall rules, since most routers block inbound traffic by default, and note that many SIM‑based carriers don’t allow incoming connections. Without port forwarding or a VPN, 192.168.8.1 will only ever work inside your Wi‑Fi.

5

My Settings for WiFi connection (which works if I close WireGuard tunnel on the phone): IP Address 192.168.8.1, Port 502. I setup WireGuard server: IP Address 10.0.0.1/24, Port 51820.

I setup both ports on router as open. I tried IP Address 10.0.0.1 and 10.0.0.1/24 with port 51820. And nothing works! With 10.0.0.1/24 my app even locked up.

6

Could you please clarify:

Previously mentioned:

  1. What is the goal of your setup?
  2. Does the SIM provide a public IP or a reachable IP within an enterprise private cellular network, or is it a CGNAT address?

Additionally:
3. What firmware version is the device running?

Please note that you will need:

  1. A SIM that provides a public IP or a reachable IP within an enterprise private cellular network in order to configure the X300B as a WireGuard VPN server and allow access from other devices
  2. When using the X300B as a WireGuard VPN server, you also need to open the port used by the RS485 TCP transparent transmission server (port 502, as you mentioned) on the X300B so that other devices can access it
  3. You can then access it using the WireGuard VPN server’s address along with the RS485 TCP transparent transmission server’s listening port (502)