无法从服务器外部访问linux上的asp.net核心mvc应用程序

Question

It's an asp.net core 2.1 mvc application hosted on an ubuntu 18.04 with Nginx. UFW is disabled. The web application was working in the beginning. When I found out it's down it has been some time.

Using a browser I go to thesite.com, the browser was redirected to https://www.thesite.com:5001/ with error:

This site can't be reached

ERR_CONNECTION_TIMED_OUT

The port number was attached so it seems at least an outside request can reach Nginx. Then inside the box when I ran

wget https://localhost --no-check-certificate

I could get index.html which is the correct response. So it seems to me the web application is taking https requests.

I have never changed default listening port, to verify, I ran this to check listening ports

sudo netstat -tnlp | grep :5001

The result shows dotnet is listening on port 5001 and 5000.

In another attempt, I used visual studio debugger to attach to the linux dotnet process, and set a few breakpoints. I could see that when using a browser the breakpoint was not reached. But when using wget like above the breakpoint was reached.

Any advice is appreciated. Thank you.

Answer 1

Well, I changed two things in /etc/nginx/sites-enabled/www.thesite.com file, and the web app is online again.

1. In the Location section, change bypass_proxy line, from http to https

2. In upstream section, change "server 127.0.0.1:5000;" to "server 127.0.0.1:5001;"

That solved the problem. Although I don't know why.

Also, I figured out how long the web app has been down, it was only one day. Because another service that was making use of the web app was working fine until the day before. I don't know why the nginx config file quit working without any change. I guess this is a special case, hopefully, it can help someone.