Nginx Reverse Proxy Subdomain for Node Applications - node.js

Question

I am quite new to NGINX configuation. I have looked through many posts looking for someone else who ran into this problem and found a working solution.
I have 2 node.js web-applications that will run on 2 separate ports (81, 82 for example).
My initial intention was to use a reverse proxy so that visitors could hit the same physical box, but be served different content based on the domain they used.
I was successful in having to separate sites render based on their domain. One of the applications has a subdomain tied to it (app.exampleb.com) and it seems that any time I try to access that subdomain, nginx serves me a page stating "that I have configured the server successfully"...... Thanks nginx.
I have placed the following in my nginx.conf file:
http {
##
# Basic Settings
##
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;
# server_names_hash_bucket_size 64;
# server_name_in_redirect off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
##
# Logging Settings
##
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
##
# Gzip Settings
##
gzip on;
gzip_disable "msie6";
# gzip_vary on;
# gzip_proxied any;
# gzip_comp_level 6;
# gzip_buffers 16 8k;
# gzip_http_version 1.1;
# gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
##
# nginx-naxsi config
##
# Uncomment it if you installed nginx-naxsi
##
#include /etc/nginx/naxsi_core.rules;
##
# nginx-passenger config
##
# Uncomment it if you installed nginx-passenger
##
#passenger_root /usr;
#passenger_ruby /usr/bin/ruby;
server {
listen 80;
server_name examplea.com;
location / {
proxy_pass http://localhost:81;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
server {
listen 80;
server_name app.examplea.com;
location / {
proxy_pass http://localhost:81;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
server {
listen 80;
server_name exampleb.com;
location / {
proxy_pass http://localhost:82;
}
}
##
# Virtual Host Configs
##
include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}

Answer 1

The full config should be this:
server {
listen 80;
server_name example.com;
location / {
proxy_pass http://localhost:81;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
Place it inside the http {} directive in nginx.conf
Remember to restart nginx