Cannot connect to server bound to loopback address. Is this intended?

[MJVville]

I'm not sure if this is intended behavior, but when I start wayvnc using the default IP 127.0.0.1 or localhost, I cannot connect to it. When I look with wireshark, it says that the computer I ran wayvnc on immediately responds to any initial SYN message with a RST message. If I start the server using the IP 0.0.0.0 or the computer's local IP 192.168.xx.xx, everything works fine. If this is not intended behavior, I can escalate this to an issue and/or provide more details. I am running sway on NixOS.

[any1]

That is the intended behaviour.

[Consolatis]

I'm not sure if this is intended behavior, but when I start wayvnc using the default IP 127.0.0.1 or localhost, I cannot connect to it.

You can actually connect to it, but only from the same system. The reason being that this IP address is only available at the loopback network interface. It is not specific to wayvnc. You can for example use this in combination with forwarding the port via a ssh connection to encrypt the VNC traffic.

0.0.0.0 on the other side binds to all IP (v4) addresses configured on the system (and thus usually all network interfaces).