Configure nginx for different ports - ruby-on-rails

Question

I have set up my nginx configuration on which I am running two websites on same port .My problem is I don't want to specify port number whenever I opening my website .I am running my websites on port 81 .My problem is if I have these two website abc.com:81 and xyz.com:81 .I need to include the port number while opening them which I don't want so can anyone tell me the possible solution ..
Here is my nginx configuration
user abc;
worker_processes 2;
error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
keepalive_timeout 65;
passenger_root /usr/local/rvm/gems/ruby-2.2.3/gems/passenger-5.0.30;
passenger_ruby /usr/local/rvm/gems/ruby-2.2.3/wrappers/ruby;
passenger_max_pool_size 50;
passenger_min_instances 5;
passenger_max_instances_per_app 0;
passenger_pool_idle_time 0;
passenger_max_preloader_idle_time 0;
passenger_app_env staging;
passenger_friendly_error_pages on;
server {
listen 81 default_server;
passenger_enabled on;
server_name abc.com;
root /var/www/project/current/public;
location / {
}
error_page 404 /404.html;
location = /40x.html {
root /var/www/project/current/public;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /var/www/project/current/public;
}
}
server {
listen 81 ;
passenger_enabled on;
root /var/www/new_project/current/public;
server_name xyz.com;
if (-f $document_root/system/maintenance.html)
{
rewrite ^(.*)$ /system/maintenance.html last;
break;
}
error_page 500 502 503 504 /500.html;
location = /500.html
{
root /var/www/new_project/current/public;
}
error_page 404 /404.html;
location = /404.html
{
root /var/www/new_project/current/public;
}
}
}

Answer 1

The default port for HTTP is port 80. Thus, if you listen on port 80, you don't need to specify the port number in the URL since clients will default to port 80 if no other port is specified in the URL.
For all other ports, it is necessary to add the port in the URL though since the client has no other way to figure out the port to connect to in any other way.