Couldn't establish network communication with server! (only some servers, HELP!)

[josesoto1993]

I bought the game recently to play with two friends but we could not establish a connection

When I try to enter his game (and many others) I get the "Couldn't establish network communication with server" error

if I create the map, I get an error indicating "Failed to determine External IP Address. Others players might not be able to connect."

We have same Factorio version (0.15.37, build 30927)

any ideas ??

[josesoto1993]

Oh, I forget, I can login in some multiplayers games...

[Raxo]

i have the same

[josesoto1993]

it was my router, use dmz and you can play :) (or at least it works for me)

[IEVERLAST]

Sounds like you need to open your ports for player connection outside your LAN.

Factorio servers use port 34197.
The port can be changed in the config file.
Factorio uses UDP only. Make sure you configure your router's port forwarding correctly. (The game builds its own "reliable delivery" layer built on UDP to deal with packet loss and reordering issues.)
Make sure there is no firewall or anti-virus blocking the UDP-packets.