Some info on firewalls
What you probably have is a firewall/router that connects to the Internet. This router has a public IP address. And it hides or "masquerades" all addresses for the computers on your internal LAN. What you need to do is to configure the router/firewall to direct TCP/IP (and UDP) traffic to the internal IP address for the GPS trackers you are using. Depending on which GPS trackers you use, you may need to open more ports. You also need to open port 80 for your web server.
You can see your firewall/routers IP address by going to this site:
The address you see there. That is the one you should enter in the GpsGate Client, or tracking device.
You can read more about IP-masquerading here on Wikipedia:
So a step by step solution is:
1. Check your public IP address
2. Configure your firewall/router to forward TCP/IP (and UDP) traffic for the port your GPS tracker is using. This is device dependent, different types of devices uses different ports.
3. Web Server. Configure your firewall/router to forward TCP/IP traffic from port 80 to address your internal IP address on port 80
4. Configure the GpsGate client or tracker to send data to the address found in step 1
Note! Please do not forget to check if you have the Windows Firewall enabled!