Change this on a per app basis.
If you have an app your device that needs to accept or listen for incoming connections, you can easily allow it do so by disabling Force Block Incoming Connections within the app settings in Portmaster.
This will allow the app to accept connections coming from anywhere. If you would rather limit where this app may connect to and accept connections from, you can easily limit it using the settings Force Block LAN and Force Block Internet Access.
If you want even more control, you can use the Incoming Rules to very specifically allow who is allowed to connect. If you use rules, be sure to select “Block everything else” from the Quick Settings menu in order to block everything you did not specifically allow.
If you don't see the "Incoming Rules" make sure you are in Advanced mode, alternatively you can search for Incoming in the search field.
You should not disable Force Block Incoming Connections in the global settings. This can be dangerous.