Login to Plesk with the admin user
On the left hand side menu bar, select Tools & Settings under the Server management section.
On the next page, click on the Firewall option under the security section.
On the Firewall page, make sure that the Firewall is ON as shown in the image. Click on Firewall Rules.
On the Firewall Rules page click on Add Firewall Rule
On the “Adding a New Rule” page, make sure the option of Switch on the rule is checked.
Specify the rule name in the box
Select all the profiles as shown in the image
For Action option click select Allow option
Specify the port range that is associated with your service or program as shown in the image and select the proper protocol as per the requirements of the service or program.
Under Remote Address box leave the default value All as it is OR if you want to restrict the access to a limited IP you can specify the IP in Add an IP address or a network box and then click on Add button.
Once you are done with filling all the values as per your requirements, click on the OK button and you can see the new firewall rule you just added.