Why does Ice connection state failed when connecting via webRTC?

Question

WebRTC

Good afternoon!
I'm trying to establish a webRTC connection between the front (tab in the browser) and the server (golang) in order to save the recording from the webcam on the server. I successfully exchange SPD and ICE candidates. As a result, both on the server and on the front, the Gathering state goes to completed, and the Ice connection state goes to checking. After some time, an event arrives on the server that Ice connection state failed. Tell me why this can happen? If necessary, I can attach pieces of code or a trace from chrome://webrtc-internals/ .

I noticed that the answer sdp from the server comes with IP 0.0.0.0, it seemed strange to me, is this normal? Now I have both the front and the server on the same computer localhost