Port forwarding in D-LINK DIR-524 router

I have Tomcat installed and I want to access it via internet. I can access it locally via localhost:8080/appname, but not from internet via http://externalip:8080/appname.

I have configured my D-LINK DIR-524 router to pass-through port 8080 as shown below. I have also turned off Windows Firewall as well as my antivirus, but still the same problem.

Any ideas?

Solution 1:

Some routers prevent loopback connections as a security feature. Most consumer-grade routers don't have any prohibition against it, it just doesn't work.

The reason it doesn't work is that the router implements request-answer algorithms, so is not programmed to handle the case where the answer is actually another request. In other words, the router implements the algorithm of request-answer rather than request-request-answer-answer.

I suggest trying this from outside of your network to see if you are getting the same results.