different Subdomains pointing to same droplet ip with different ports
I am trying have different sub domains resolving to the same IP (same droplet) but with different ports, pointing to single nginx server; which in turn points to apache.
I am trying to set some thing like this .
example.com point to droplet ip with port 80
dev.example.com point to droplet ip with port 8081
info.example.com point to droplet ip with port 8080
and so on.
I have currently set up nginx to listen to port 80 and forward to apache @ port 8080 which works fine.
But I am confused how should go about to do the same for sub domains.
I set up the nginx server soley ofr proxy server as several article point to same, iam not sure this is re right direction I am in.
i did find a similar question https://www.digitalocean.com/community/questions/subdomains-pointing-to-same-droplet-in-different-ports
but the answer here is not exactly what my question is and also very vague for a beginner like me.
Any help in this regard will be highly appreciated.