Hi there, Shibi
I’m still new here, but I runned into a similar situation last week. The easiest way to use your domain for two different servers is by using a sub-domain. You can do that by creating an A Record on your DNS provider specifying the hostname as sub-domain.your-domain.com, or just the sub-domain, and then point out the IP of the discourse instance.
This article may help with the above solution.
The solution I suggested above may help you with that. I think this way of using it as a resource for your other application may be harder to set up.
By using the official cloud setup script, it will run on port 80 by default.
Could you please give more details on that?
If you do so, you won’t be able to send any emails like invitations and account register confirmations. But probably you can’t ignore the smtp setup.
By the way, 443 is the HTTPS port, it is used to establish the encryption. This means your domain is probably not configured correctly and the Discourse setup is not being able to reach your server.