This issue was resolved by setting up the port forward as described on the Factorio Wiki: https://wiki.factorio.com/Multiplayer#S ... layer_Game

I'm not sure why i was able to join some servers but not others without the port forward, but setting up UDP on 34197 worked.

So if we are talking about a dedicated host server, that's got to be the standalone version, i.e. non-Steam. Obviously the Steam and Standalone versions should be identical, but that the is the only thing I can figure that is causing this multiplayer issue. If I'm wrong, I would love to be corrected...

Greetings, Tacker. It seems you have the same problem I have with joining specific multiplayer servers. Same symptoms: no ping in server list, server does not see a join attempt, local game tries to sync mods, others can join the server but you can't. See thread here: https://forums.factorio.com/vie...

Yarp. Here's my log when trying to join. When i view the server on the multiplayer game list, the ping does not resolve and says "can't reach". 20.996 Info UDPSocket.cpp:27: Opening socket at (IP ADDR:({0.0.0.0:0})) 44.950 Info UDPSocket.cpp:218: Closing socket 44.951 Info UDPSocket.cpp:24...

"Couldn't establish network communication with the server." is the error message when trying to join friend's hosted server. Friend and i can both join a random MP server in the server list, but i cannot join his server from the server list or by IP. We have configured firewall settings on...