title: How to connect to localhost using external IP address?
body: <p>I've searched in general, and looked at suggested responses here, so I hope this isn't immediately marked as a duplicate. So here goes.  </p>
  
  <p>I'm building a simple web app with an Angular server using port 3000 on my desktop. I've been testing it with the standard "localhost:3000" URL. I then wanted to make it accessible to others outside my home for testing and review. So I did the expected port forwarding in my router of port 3000 to my local machine at 10.0.0.90. I then constructed a link using my external IP (router's "WAN IP") like "[wan ip]:3000". And this has worked as expected, enabling external access as well as internal access. The only thing funny at the time was having to add "--host 0.0.0.0" to the server invocation.</p>
  
  <p>But here's the problem. My original setup, where everything worked, was a Comcast modem with my router (TP-Link) hanging off of it. Recently, I switched to their Xfinity Gateway combo modem/router (Arris TG1682G). Now, I can't get to the server using the [wan ip]:3000 URL. I can't even ping that URL, they all time out. So, while on the phone with Comcast tech support, and not being able to determine why I had this problem (even after upgrading router firmware and rebooting it), I asked him to try [wan ip]:3000, and it worked! It also doesn't work from any other machines on my local network. But, when I changed my laptop wireless connection from my house Xfinity router to an external one (one of the many "xfinitywifi"s seen in a list of networks, besides numerous neighbors), it again worked! Poking around in Xfinity router admin pages, I didn't see anything that sounded like it was involved with this.</p>
  
  <p>So, any idea what's going on, and how to fix? Thanks for any ideas or guidance.</p>