I'm looking for a way to do voice chatting over my LAN without an Internet connection. The two machines both run Linux (they are Raspberry Pis, with the latest Raspbian Stretch Lite installed).
Programs like Skype won't do the job, because they require an Internet connection and only run with a GUI. TeamSpeak would probably run without an Internet connection, but I don't think that there is a way to start it without a desktop environment.
Do you know a program that would meet these requirements? Preferably an open source solution?