QuickBooks Point of Sale ports, the following processes can be interrupted: Electronic Funds Transfer – Intuit Merchant Service credit card processing.
Database Server Manager – (Server installation only) Ability to connect and write to company file
Intuit Entitlement Service – Product license and user validation.
Attempt following steps and configure a Windows firewall for QuickBooks Point of Sale:
1:- Configure Windows firewall
2:- On your keyboard, press Windows+R to open the run command.
3:- Type in control and click OK to open the Control Panel.
4:- Set the “view by” to Small Icons and select Windows Firewall.
5:- Select Advanced Settings and click Inbound.
6:- Click New Rule.
7:- Select Port and click Next.
8:- Enter the port numbers and click Next (See Point of Sale Firewall Ports section).
9:- Select Allow Connection and click Next.
10:- Name your firewall rule (e.g. POS) and click Finish
11:- Follow steps 5-9 to create a new Outbound Rule.
If any problem occurs after performed above steps contact QuickBooks Customer Support
If you want to more detail about this visit here Firewall configuration for QuickBooks Point of Sale