Ok my title is a little bit convoluted. Allow me to explain.
I have a server in my LAN that listens for HTTP connections at let's say
192.168.1.10:1234. I can access this address from my other computers and everything works as expected.
Now to access this server from the Internet I have forwarded the port 5678 to the port 1234.
If I go to a PC outside my house and enter
188.8.131.52:5678 (my ISP address with the forwarded port) in the web browser, I am able to access my server.
If I do the same exactly thing from within my LAN I get a timeout error.
What is wrong here?
(I am newbie in networking so please forgive my ignorance.)