nginx (nginx/1.10.0 ) not working after ubuntu OS upgrade - amazon-web-services

Question

I upgraded ubuntu and after up-gradation, example.com (name changed) stopped working and giving below error. I am using nginx (nginx/1.10.0 ) and ubuntu (release 16.04). The whole setup is on AWS EC2
502 Bad Gateway
Below are contents from nginx error log
[error] 1201#1201: *27 connect() failed (111: Connection refused) while connecting to upstream, client: 171.76.106.51, server: example.com, request: "GET /favicon.ico HTTP/1.1", upstream: "http://127.0.0.1:3000/favicon.ico", host: "public IP", referrer: "https://publicIP/"
Below is nginx.conf file
user www-data;
worker_processes 4;
pid /run/nginx.pid;
events {
worker_connections 768;
# multi_accept on;
}
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";
include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}
nginx sites-enabled default has symlink to sites-available default and below is the content
server {
listen 80 default_server;
listen [::]:80 default_server ipv6only=on;
root /usr/share/nginx/html;
index index.html index.htm;
# Make site accessible from http://localhost/
server_name localhost;
location / {
try_files $uri $uri/ =404;
}
}
Another nginx conf file
server {
listen 443 ssl;
server_name example.com;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_ciphers 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';
root /usr/share/nginx/html;
index index.html index.htm;
# Make site accessible from http://localhost/
server_name localhost;
location / {
proxy_pass http://localhost:3000/;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forward-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forward-Proto http;
proxy_set_header X-Nginx-Proxy true;
proxy_redirect off;
}
}
server {
listen 80;
server_name example.com;
return 301 https://$host$request_uri;
}
When I am doing http://localhost:3000/ it says connection refused
Resolving localhost (localhost)... 127.0.0.1
Connecting to localhost (localhost)|127.0.0.1|:3000... failed: Connection refused.
When I am doing "wget www.google.com" its says connected
Can you please help here ?