Why is not visible the local server from the Internet?

The essence is this:
Your local network has the RPi to the server on port 30003. The server is available from the local network and I want it to be accessible from the Internet.
For this I set up a port forward rule on the router and use a Dynamic DNS service because I have gray ip.
When I go to the address with the DNS service without specifying the port, I see the admin panel of your router. And if you add the right port, the browser cannot establish a connection.
What could be the reason?
July 2nd 19 at 13:51
3 answers
July 2nd 19 at 13:53
Solution
Several possible reasons:
1. Transfer port is incorrectly configured
2. firewall blocks connections from outside to port
3. The server's listening port 30003, accepts connections only from local area

The third option you can check with the command:
sudo netstat-tulpn
1. Similar to portforwarding on the same piece of metal works
2. As you can see (RPi3, latest Raspbian)?
3. That's the right port:
` tcp 0 0 0.0.0.0:30002 0.0.0.0:* LISTEN 939/fr24feed - Jaunita.Glov commented on July 2nd 19 at 13:56
30002 or 30003 in question? - Daphne_Roob commented on July 2nd 19 at 13:59
OK, will delete the comment. - Daphne_Roob commented on July 2nd 19 at 14:02
in General, both. And both are not working. - Jaunita.Glov commented on July 2nd 19 at 14:05
July 2nd 19 at 13:55
Solution
"For this I have configured port forwarding on the router and use a Dynamic DNS service because I have gray ip."
If you have gray IP, the Dynamic DNS will not help you. It helps if you have a non-static white IP.

Well, examples of IP addresses would be nice, because apparently you have something nedostroi, but without figures we can only guess
July 2nd 19 at 13:57
Solution
In General, the problem like as dared. The server is not responding, if we look at the dynamic dns address from the same local network. Via mobile Internet, for example, everything works.

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