Here is how to allow spesific IP & Port via UFW
Say if we want to allow 121.111.231.234 with port 3310 on TCP, you can type :
sudo ufw allow from 121.111.231.234 proto tcp to any port 3310
you can view the result :
To delete the rules with :
sudo ufw delete allow from 10.0.0.46 proto tcp to any port 3310