I have my own TS 3 server.
I do use Avast as my Anti-virus program and renew my license once a year.
Friends cannot connect to my TS server. I have done the following:
I have made an exception to TS 3 Server in the firewall
Is your firewall network profile in private or puplic mode?
Setting up Firewall Application Rules in Avast Antivirus
https://support.avast.com/en-eu/article/Antivirus-Firewall-Application-Rules
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NOTE:The Network profiles control the settings which determine how strictly Firewall protects your PC.
Private: a lower level of security suitable for when your PC is connected to a trusted network such as your home or work network.
This profile enables better connectivity, and permits all communication within the network.
Public: a higher level of security suitable for when your PC is connected to a public network such as in a cafe or airport.
Because public networks present greater security risks, no incoming communication is permitted when this profile is set.
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