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Solving issue of port 16000 blocked even after portforward
So you have set up your Options.ini, you made the exceptions in the firewall and you've finally done the portforwarding people told you about... but you still can't connect to players, and the port tester fails to connect.
Finding the reason can be difficult, but a common problem that not many people know about is actually caused by your ISP (internet service provider). Most addresses you will find on the internet use the protocol IPv4, however this type of IP has been around for a long time and the addresses are running out. There is another protocol called IPv6, which will fix this issue, but it takes time to transition to this protocol with already established services. So in the meantime, a lot of ISPs have resorted into using something called Carrier-Grade Network Address Translation or CGNAT/CGN for short. This technology allows multiple users to share the same public IP-address, saving address-space.
A regular NAT takes a Private IP (the IP used on your home network to identify your computer, 192.168.1.25 for example), then converts it into a Public IP (the IP displayed on the internet, 85.132.133.196 for example). The difference between this and CGNAT is that multiple users behind a cgnat will share the same Public IP, but each user connected with this IP will be logged with a tag to identify where the traffic should be routed back to. Since this means you do not have your own unique IPv4 address but rather shares one with other people, it also means that you cannot control the ports for this IP and thus portforwarding is not possible. Your ISP is in control of the ports and if they do not have the specific port you need open, in this case 16000 udp, this is most likely what is causing the connection problems. (note: this explanation is simplified)
So how do you know if you're behind CGNAT? First you can see if your public IP displayed on websites such as whatismyip.com is the same as the WAN IP listed in your router settings. If they are not the same, chances are you're behind cgnat. Some routers don't show WAN IP in the settings, sadly. But the best way to find out is to call your ISP and ask if you are behind a CGNAT or NAT444. If they say you are, tell them that you want it gone and you need a dedicated Public IP. Some ISPs will do this for free, others will charge you a small fee for it. Some even state on their website that they are using this technology so you can make sure beforehand that it's their doing.
If you want a more detailed explanation follow these links:
https://chrisgrundem...cgn-lsn-breaks/
https://www.a10netwo...rier-grade-nat/
https://www.networkw...-grade-nat.html
Edit: Made it easier to understand while including links to more detailed explanations.
I'm not yet entirely sure this is what's causing my issue, I still need to ask my ISP to provide me with a public IP to test it, but I've been searching for DAYS why all the instructions I've been following didn't work. This should be pinned with the other set of "Network issues" potential solutions.
