Couldn't establish network communication with server

[Zoro]

I am trying to set up a multiplayer game with my niece. When I create a game and she tries to connect, she gets the "Couldn't establish network communication with server" error. When she creates a game and I try to connect, I get the same error. I have configured my router for forwarding on port 34197. The attached log was saved shortly after the last connect attempt failed. Has anyone written a troubleshooting checklist for multiplayer connection problems?

[Zoro]

Yesterday, I was not able to create a multiplayer game with my niece. She was connected to the internet from her house and I from mine. When either one of us hosted a multiplayer game, the other could see it under "Browse public games", but we could not connect. We got the "Couldn't establish network communication with server" every time (as described in my earlier post).

Today, I'm trying to debug the problem without my niece's help. I have two computers on my desk. I'm logged into one with my Factorio account and the other with hers. I have fiddled with the settings in Windows Firewall, but I still cannot create a multiplayer game through "Browse public games". I've discovered that I can create a multiplayer game through "Play on LAN".

Question: If I have two computers on the same LAN, should it be possible to create a multiplayer game through "Browse public games"?