You can use the TAPI- lines from https://uacsta.de/ and from https://ip-softphone.de/ easy to use locally or easily on a server (z.B. terminal server) centrally for up to 255 - also any mixed clients.
In this compact tutorial you will learn which settings have to be made in the firewall of the server .
Activate port 21077 on the firewall on the server if no VPN is used : All transmitted data are encrypted. Please note that the Server- firewall allows the initial port (in the example "21077" TCP) for incoming data or use the TAPI-Server environment for security reasons better in a VPN environment. Without VPN you have to configure the Windows firewall z.B. in just a few steps
With the required Restart the changes will take effect .
Click hereto get back to the TAPI-Server tutorial .