I have tried many times , and the App server is reachable from LB host and not from other app servers. Still I am facing the issue.
The following commsnd I used to do the same
sudo yum install -y iptables iptables-services
sudo systemctl enable iptables
sudo systemctl start iptables
sudo iptables -I INPUT -p tcp -s 172.16.239.4 --dport 3003 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 3003 -j DROP
sudo iptables -L -n --line-numbers
sudo service iptables save