Nodejs reverse proxy server (nginx)

I have already running 2 servers at digital ocean and I installed nginx for webserver and nodejs for app server.

For app server : Nodeapp Directory : /var/appdata/myapp/ Nodejs app running at 4680 Port; However in the app server I have couple iptables options(firewall)

IPTABLES Options I did for appserver:

*filter

# Default policy is to drop all traffic
-P INPUT DROP
-P FORWARD DROP
-P OUTPUT DROP

# Allow all loopback traffic
-A INPUT -i lo -j ACCEPT
-A OUTPUT -o lo -j ACCEPT

# Allow ping.
-A INPUT -p icmp -m state --state NEW --icmp-type 8 -j ACCEPT

# Allow incoming SSH, HTTP and HTTPS traffic
-A INPUT -i eth0 -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT
-A OUTPUT -o eth0 -p tcp -m multiport --sports 22,80,443 -m state --state ESTABLISHED -j ACCEPT

# Allow inbound traffic from established connections.
# This includes ICMP error returns.
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Log what was incoming but denied (optional but useful).
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables_INPUT_denied: " --log-level 7

# Allow outgoing SSH, HTTP and HTTPS traffic
# This is useful because we won't be able to download and install 
# NPM packages otherwise and use git over SSH
-A OUTPUT -o eth0 -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT
-A INPUT -i eth0 -p tcp -m multiport --sports 22,80,443 -m state --state ESTABLISHED -j ACCEPT

# Allow dns lookup
-A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT
-A INPUT -p udp -i eth0 --sport 53 -j ACCEPT

# Set rate limits for DOS attack prevention (optional)
# The rates here greatly depend on your application
-A INPUT -p tcp -m multiport --dports 80,443 -m limit --limit 250/minute --limit-burst 1000 -j ACCEPT

# Log any traffic which was sent to you
# for forwarding (optional but useful).
-A FORWARD -m limit --limit 5/min -j LOG --log-prefix "iptables_FORWARD_denied: " --log-level 7

COMMIT

For Webserver default config is like this-

    listen 80 default_server;
    listen [::]:80 default_server;

    # SSL configuration
    #
    # listen 443 ssl default_server;
    # listen [::]:443 ssl default_server;
    #
    # Note: You should disable gzip for SSL traffic.
    # See: https://bugs.debian.org/773332
    #
    # Read up on ssl_ciphers to ensure a secure configuration.
    # See: https://bugs.debian.org/765782
    #
    # Self signed certs generated by the ssl-cert package
    # Don't use them in a production server!
    #
    # include snippets/snakeoil.conf;

    root /var/www/html;

    # Add index.php to the list if you are using PHP
    index index.html index.htm index.nginx-debian.html;

    server_name _;

    location / {
            proxy_pass http://10.135.9.223:4680 ;
            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;
    }

With All these option I almost write down everything I guess but if anything missed pls let me tell. So the main problem here is when I enter url for http://web-server-ip-address it responds 504 gateway timed out

EDIT : When I disable the firewall there is no problem.

Solution

Disabled the firewall and take an advantage on cloudflare if you're not familiar with those types of errors