The phone sends the call information per Action URLs to the specified TCP port on your PC. The TCP port must therefore be enabled in your (Windows-) firewall. If you use a different firewall, you must configure it manually.

If the filrewall blocks incoming TCP connections, you don't get any TAPI call events.

Example configuration of Windows 11 firewall for TCP port 8080:

1. Open the firewall configuration by: [Start > Settings] and enter "Firewall" in the search bar at the top. Select "Windows Defender Firewall" from the search results.
2. Click [Advanced Settings] on the left. A new window will open.
3. Click [Incoming Rules] on the left and then [New Rule...] on the right.
4. Select "Port" as the rule type and click [Next...].
5. Select "TCP" and enter 8080 in the "Specific Local Ports" field.
6. Next, confirm "Allow connection".
7. In the next step, "Profile," only the "Domain" and "Private" boxes should be checked.
8. In the final step, enter a name. For example: "enable TCP port 8080 for snom TAPI"

Tip: Command file for automatic firewall configuration:win_firewall_cfg.cmd