failed (111: Connection refused) while connecting to upstream with nginx

Getting failed (111: Connection refused) while connecting to upstream

I've commented out a few things I have tried. Not sure why this isn't working as expected.

I have a server running on 4000 and I'm not sure where to go from here. I deleted the default configuration as well.

server { 
       #  listen        0.0.0.0:80;
       listen           80;
        # listen        127.0.0.1;
        listen          [::]:80;
        server_name     rotb.io www.rotb.io;


        location / {
        #       proxy_set_header   X-Forwarded-For $remote_addr;
        #       proxy_set_header   Host $http_host;
                proxy_pass http://127.0.0.1:4000/;

        }
}