Cant connect to TcpListener

I'm reimplementing my old voice chat app (written in C++) in Rust, finished the first version, tested all locally. Now starting to test it on different machines and can't connect to the server. I have 2 PCs in one local network, one is running a server app and the other is running a client app. The TcpStream::connect() just returns 'connection refused'. The server has a firewall rule for the needed port. I know that it should work because I tried exactly the same thing but with my app in C++. I even tried just starting my old C++ server app and TcpStream::connect() to it from a different machine in Rust - it works, but no matter what I can't connect to my Rust server. Moreover, I tried a simple example code from std::net::TcpListener - Rust, and it's also not working.
So, any ideas on how to investigate this?

What ip did you bind the listener to?

127.0.0.1, just like in the example.

Change it to 0.0.0.0

yep :), thanks, gotta read about the difference.